From 48be80d01d904bd3b2cf575ef0e61057c640ea22 Mon Sep 17 00:00:00 2001
From: Adrian Sieber <36796532+ad-si@users.noreply.github.com>
Date: Thu, 10 Apr 2025 10:37:23 +0000
Subject: [PATCH 1/4] Upgrade to GHC 9.6.6 (#4568)

* Upgrade CI

* Back to the previous haskell image

* Use new spavo

* Upgrade node to latest supported lts

* Upgrade to GHC 9.6.6

- Switch from `ansi-wl-pprint` to `prettyprinter`
- Add several `extra-deps`

* Upgrade CI to use GHC 9.6.6

* Upgrade GitHub Actions

* CI: Upgrade to macos-15, specify exact version of Ubuntu

* CI: Upgrade Stack from 2.15.1 to 3.3.1

* CI: Include stack.yaml.lock file and use it for the cache's file hashes

* CI: Also include `purescript.cabal` in cache's file hashes

* Update documentation

* CI: Remove obsolete directory ownership changes

* CI: Add safe.directory configuration for Ubuntu 24.04

* CI: Fix container ownership issues in workflow configuration

* CI: Simplify container configuration and fix working directory ownership for Ubuntu 24.04

* Update version ranges of dependencies

* Update Cabal version range and allow newer dependencies in stack configuration

* Update Cabal version to 3.10.3.0 in stack configuration

* Enable allow-newer option in stack configuration

* Update dependency versions in purescript.cabal and stack.yaml

* Update weeder installation and streamline CI workflow

* Fix wrapping of run commands

* Remove obsolete quotes

* Add missing `--name` flag to `spago init`

* Add Adrian Sieber to contributors

* Add changelog entry for GHC upgrade

* Use new weeder.toml config file format

* Install missing `jq` dependency

* CI: Use `-y` flag for all `apt-get install` runs

* Vendor pattern-arrows

* Run haskell container on ubuntu-latest, use macos-13 and macos-14

* CI: Use strings instead of arrays for matrix.os

* Fix Hlint warnings

* Add arm64 Linux to testing matrix

* Correctly match only self-hosted Linux runner

* Don't use self-hosted runners anymore, as GitHub runners cover all cases

* Mention glibc bump from `2.28` to `2.31` in changelog

* Upgrade to latest version of aeson-better-errors from Hackage

* Remove obsolete `allow-newer` section, delete .stack-work on make clean

* Re-add `allow-newer` block, improve dependency bounds

* Downgrade haskeline to 0.8.2 to avoid libtinfo issues

* Update aeson-better-errors and use cheapskate fork

* Fix build errors in stack

These errors are present in the Cabal build and seem to be caused
by Cabal and Stack using different versions of mtl, with 2.3.x notably
changing re-exports for certain modules.

---------

Co-authored-by: Fabrizio Ferrai <fabrizio.ferrai@gmail.com>
Co-authored-by: Justin Garcia <purefunctor@gmail.com>
---
 .github/workflows/ci.yml                      | 121 +++++++-----------
 .gitignore                                    |   1 -
 CHANGELOG.d/internal_upgrade_to_ghc_9.6.md    |   2 +
 CONTRIBUTORS.md                               |   1 +
 INSTALL.md                                    |   5 +-
 LICENSE                                       |  24 ----
 Makefile                                      |   5 +
 app/Command/Docs.hs                           |  15 ++-
 app/Main.hs                                   |   9 +-
 cabal.project                                 |   5 +
 ci/build-package-set.sh                       |  16 +--
 purescript.cabal                              |  47 +++----
 src/Control/Monad/Supply/Class.hs             |   2 +
 src/Control/PatternArrows.hs                  | 118 +++++++++++++++++
 src/Language/PureScript/CodeGen/JS.hs         |   1 -
 .../PureScript/CoreImp/Optimizer/TCO.hs       |   2 +-
 .../Docs/RenderedCode/RenderType.hs           |   4 +-
 src/Language/PureScript/Linter/Exhaustive.hs  |   1 -
 src/Language/PureScript/Pretty/Types.hs       |   4 +-
 .../PureScript/Sugar/BindingGroups.hs         |   6 +-
 src/Language/PureScript/TypeChecker/Monad.hs  |   1 +
 .../PureScript/TypeChecker/Synonyms.hs        |   1 +
 stack.yaml                                    |  30 ++---
 stack.yaml.lock                               |  58 +++++++++
 update-changelog.hs                           |   3 +-
 weeder.dhall                                  |  41 ------
 weeder.toml                                   |  40 ++++++
 27 files changed, 347 insertions(+), 216 deletions(-)
 create mode 100644 CHANGELOG.d/internal_upgrade_to_ghc_9.6.md
 create mode 100644 src/Control/PatternArrows.hs
 create mode 100644 stack.yaml.lock
 delete mode 100644 weeder.dhall
 create mode 100644 weeder.toml

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 2cd314dbf1..3557db1a6f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -20,6 +20,7 @@ on:
       - purescript.cabal
       - Setup.hs
       - stack.yaml
+      - stack.yaml.lock
       - update-changelog.hs
       - weeder.dhall
   release:
@@ -32,7 +33,7 @@ defaults:
 env:
   CI_PRERELEASE: "${{ github.event_name == 'push' && github.ref == 'refs/heads/master' }}"
   CI_RELEASE: "${{ github.event_name == 'release' }}"
-  STACK_VERSION: "2.15.1"
+  STACK_VERSION: "3.3.1"
 
 concurrency:
   # We never want two prereleases building at the same time, since they would
@@ -53,16 +54,18 @@ jobs:
       fail-fast: false # do not cancel builds for other OSes if one fails
       matrix:
         include:
-          - # If upgrading the Haskell image, also upgrade it in the lint job below
-            os: ["ubuntu-latest"]
-            image: haskell:9.2.8@sha256:b3b2f3909c7381bb96b8f18766f9407a3d6f61e0f07ea95e812583ac4f442cbb
-          - os: ["macOS-14"]
-          - os: ["windows-2019"]
-          - os: ["self-hosted", "macos", "ARM64"]
-          - os: ["self-hosted", "Linux", "ARM64"]
+          - image: haskell:9.6.6  # Also upgrade version in the lint job below
+            os: ubuntu-latest  # Exact version is not important, as it's only the container host)
+
+          - image: haskell:9.6.6
+            os: ubuntu-24.04-arm  # Exact version is not important, as it's only the container host
+
+          - os: macos-13  # x64
+          - os: macos-14  # arm64
+          - os: windows-2019  # x64
 
     runs-on: "${{ matrix.os }}"
-    container: "${{ matrix.image }}"
+    container:  "${{ matrix.image }}"
 
     outputs:
       do-not-prerelease: "${{ steps.build.outputs.do-not-prerelease }}"
@@ -71,43 +74,40 @@ jobs:
     steps:
       - # We need `gh` installed on the Linux version. Otherwise, release artifacts won't be uploaded.
         name: "(Linux only) Install gh"
-        if: "contains(matrix.os, 'ubuntu-latest')"
+        if: startsWith(matrix.image, 'haskell')
         run: |
           curl -fsSL https://cli.github.com/packages/githubcli-archive-keyring.gpg | dd of=/usr/share/keyrings/githubcli-archive-keyring.gpg
           chmod go+r /usr/share/keyrings/githubcli-archive-keyring.gpg
           echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/githubcli-archive-keyring.gpg] https://cli.github.com/packages stable main" | tee /etc/apt/sources.list.d/github-cli.list > /dev/null
           apt-get update
-          apt-get install gh
+          apt-get install -y gh
 
-      - uses: "actions/checkout@v2"
-      - uses: "actions/setup-node@v2"
+      - uses: "actions/checkout@v4"
+      - uses: "actions/setup-node@v4"
         with:
-          node-version: "16"
+          node-version: "22"
 
       - id: "haskell"
         name: "(Non-Linux only) Install Haskell"
-        # Note: here we exclude the self-hosted runners because this action does not work on ARM
-        # and their Haskell environment is instead provided by a nix-shell
-        # See https://github.com/purescript/purescript/pulls/4455
-        if: "!contains(matrix.os, 'ubuntu-latest') && !contains(matrix.os, 'self-hosted')"
+        if: startsWith(matrix.os, 'macos') || startsWith(matrix.os, 'windows')
         uses: "haskell-actions/setup@v2"
         with:
+          ghc-version: "9.6.6"
           enable-stack: true
           stack-version: "${{ env.STACK_VERSION }}"
           stack-no-global: true
 
-      - name: "(Linux only) Check Stack version and fix working directory ownership"
-        if: "contains(matrix.os, 'ubuntu-latest')"
+      - name: "(Linux only) Fix working directory ownership"
+        if: startsWith(matrix.image, 'haskell')
         run: |
-          [ "$(stack --numeric-version)" = "$STACK_VERSION" ]
           chown root:root .
 
-      - uses: "actions/cache@v2"
+      - uses: "actions/cache@v4"
         with:
           path: |
             /root/.stack
             ${{ steps.haskell.outputs.stack-root }}
-          key: "${{ matrix.image || runner.os }}--MdyPsf-${{ hashFiles('stack.yaml') }}"
+          key: "${{ matrix.image || runner.os }}--MdyPsf-${{ hashFiles('stack.yaml.lock', 'purescript.cabal') }}"
 
       - name: "(Windows only) Configure Stack to store its programs in STACK_ROOT"
         # This ensures that the local GHC and MSYS binaries that Stack installs
@@ -122,16 +122,16 @@ jobs:
         run: "ci/fix-home ci/build.sh"
 
       - name: "(Linux only) Glob tests"
-        if: "contains(matrix.os, 'ubuntu-latest')"
+        if: startsWith(matrix.image, 'haskell')
         working-directory: "sdist-test"
         # We build in this directory in build.sh, so this is where we need to
         # launch `stack exec`. The actual glob checks happen in a temporary directory.
         run: |
-          apt-get install tree
+          apt-get install -y tree
           ../ci/fix-home stack exec bash ../glob-test.sh
 
       - name: "(Linux only) Build the entire package set"
-        if: "contains(matrix.os, 'ubuntu-latest')"
+        if: startsWith(matrix.image, 'haskell')
         # We build in this directory in build.sh, so this is where we need to
         # launch `stack exec`. The actual package-set building happens in a
         # temporary directory.
@@ -144,11 +144,11 @@ jobs:
         # Moreover, npm has a hook issue that will cause spago to fail to install
         # We upgrade npm to fix this
         run: |
-          npm i -g npm@8.8.0
+          apt-get install -y jq
           ../ci/fix-home stack --haddock exec ../ci/build-package-set.sh
 
       - name: Verify that 'libtinfo' isn't in binary
-        if: "runner.os == 'Linux'"
+        if: runner.os == 'Linux'
         working-directory: "sdist-test"
         run: |
           if [ $(ldd $(../ci/fix-home stack path --local-doc-root)/../bin/purs | grep 'libtinfo' | wc -l) -ge 1 ]; then
@@ -157,17 +157,6 @@ jobs:
             exit 1
           fi
 
-      - name: "(Self-hosted Linux ARM64 only) Patch the binary to work on non-Nix systems"
-        if: "runner.os == 'Linux' && runner.arch == 'ARM64'"
-        working-directory: "sdist-test"
-        # The self-hosted build happens inside a nix-shell that provides a working stack binary
-        # on ARM systems, and while the macOS binary is fine - because macOS binaries are almost
-        # statically linked), the linux ones are all pointing at the nix store.
-        # So here we first point the binary to the right linker that should work on a generic linux,
-        # and then fix the RUNPATH with the right location to load the shared libraries from
-        run: |
-          patchelf --set-interpreter /usr/lib/ld-linux-aarch64.so.1 --set-rpath /usr/lib/aarch64-linux-gnu $(stack path --local-doc-root)/../bin/purs
-
       - name: "(Release/prerelease only) Create bundle"
         if: "${{ env.CI_RELEASE == 'true' || env.CI_PRERELEASE == 'true' && steps.build.outputs.do-not-prerelease != 'true' }}"
         run: |
@@ -199,7 +188,7 @@ jobs:
 
       - name: "(Prerelease only) Upload bundle"
         if: "${{ env.CI_PRERELEASE == 'true' && steps.build.outputs.do-not-prerelease != 'true' }}"
-        uses: "actions/upload-artifact@v3"
+        uses: "actions/upload-artifact@v4.6.0"
         with:
           name: "${{ runner.os }}-${{ runner.arch }}-bundle"
           path: |
@@ -208,59 +197,39 @@ jobs:
 
       - name: "(Release only) Publish bundle"
         if: "${{ env.CI_RELEASE == 'true' }}"
-        # This requires the gh command line tool to be installed on our
-        # self-hosted runners
         env:
           GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
         run: "gh release upload --clobber ${{ github.ref_name }} sdist-test/bundle/*.{tar.gz,sha}"
 
   lint:
-    runs-on: "ubuntu-latest"
-    # At the moment, this is a different image from the image used for
-    # compilation, though the GHC versions match. This is because the
-    # compilation image uses an old version of glibc, which we want because it
-    # means our published binaries will work on the widest number of platforms.
-    # But the HLint binary downloaded by this job requires a newer glibc
-    # version.
-    container: haskell:9.2.8@sha256:b3b2f3909c7381bb96b8f18766f9407a3d6f61e0f07ea95e812583ac4f442cbb
+    container: haskell:9.6.6
+    runs-on: ubuntu-latest  # Exact version is not important, as it's only the container host
 
     steps:
-      - uses: "actions/checkout@v2"
+      - uses: "actions/checkout@v4"
 
       - name: "Fix working directory ownership"
         run: |
           chown root:root .
 
-      - uses: "actions/cache@v2"
+      - uses: "actions/cache@v4"
         with:
           path: |
             /root/.stack
-          key: "lint-${{ hashFiles('stack.yaml') }}"
+          key: "lint-${{ hashFiles('stack.yaml.lock', 'purescript.cabal') }}"
 
       - run: "ci/fix-home ci/run-hlint.sh --git"
         env:
           VERSION: "3.5"
 
-      # Note: the weeder version will need to be updated when we next update our version
-      # of GHC.
-      #
-      # weeder-2.2.0 has somewhat strange version deps. It doesn't appear to
-      # support the exact versions of dhall and generic-lens in LTS-18.
-      # However, forcing it to use the versions of dhall and generic-lens in
-      # LTS-18 doesn't cause any problems when building, so the following
-      # commands build weeder while ignoring version constraints.
       - name: Install weeder
         run: |
-          # The `stack.yaml` file is copied to a separate file so that
-          # adding `allow-newer: true` doesn't affect any subsequant
-          # calls to `stack`.
-          cp stack.yaml stack-weeder.yaml
-          # `allow-newer: true` is needed so that weeder-2.2.0 can be
-          # installed with the dependencies present in LTS-18.
-          echo 'allow-newer: true' >> stack-weeder.yaml
-          ci/fix-home stack --no-terminal --jobs=2 build --copy-compiler-tool --stack-yaml ./stack-weeder.yaml weeder-2.4.0
+          ci/fix-home stack --no-terminal --jobs=2 \
+            build --copy-compiler-tool weeder-2.8.0
 
-      - run: "ci/fix-home stack --no-terminal --jobs=2 build --fast --ghc-options -fwrite-ide-info"
+      - run: |
+          ci/fix-home stack --no-terminal --jobs=2 \
+            build --fast --ghc-options -fwrite-ide-info
 
       - run: "ci/fix-home stack exec weeder"
 
@@ -268,26 +237,28 @@ jobs:
       # reference from our test suite to count in the above check; the fact
       # that a function is tested is not evidence that it's needed. But we also
       # don't want to leave weeds lying around in our test suite either.
-      - run: "ci/fix-home stack --no-terminal --jobs=2 build --fast --test --no-run-tests --ghc-options -fwrite-ide-info"
+      - run: |
+          ci/fix-home stack --no-terminal --jobs=2 \
+            build --fast --test --no-run-tests --ghc-options -fwrite-ide-info
 
       - run: "ci/fix-home stack exec weeder"
 
   make-prerelease:
-    runs-on: "ubuntu-latest"
+    runs-on: ubuntu-latest
     needs:
       - "build"
       - "lint"
     if: "${{ github.event_name == 'push' && needs.build.outputs.do-not-prerelease != 'true' }}"
     steps:
-      - uses: "actions/download-artifact@v3"
+      - uses: "actions/download-artifact@v4"
       - uses: "ncipollo/release-action@v1.10.0"
         with:
           tag: "v${{ needs.build.outputs.version }}"
           artifacts: "*-bundle/*"
           prerelease: true
           body: "This is an automated preview release. Get the latest stable release [here](https://github.com/purescript/purescript/releases/latest)."
-      - uses: "actions/checkout@v3"
-      - uses: "actions/setup-node@v3"
+      - uses: "actions/checkout@v4"
+      - uses: "actions/setup-node@v4"
         with:
           node-version: "16.x"
           registry-url: "https://registry.npmjs.org"
diff --git a/.gitignore b/.gitignore
index 0454beffcb..73b2b4678f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,7 +3,6 @@ bin
 dist
 cabal-dev
 .cabal-sandbox
-stack.yaml.lock
 cabal.sandbox.config
 dist-newstyle/
 cabal.project.local*
diff --git a/CHANGELOG.d/internal_upgrade_to_ghc_9.6.md b/CHANGELOG.d/internal_upgrade_to_ghc_9.6.md
new file mode 100644
index 0000000000..6622b6baed
--- /dev/null
+++ b/CHANGELOG.d/internal_upgrade_to_ghc_9.6.md
@@ -0,0 +1,2 @@
+* Upgrade GHC to [`9.6.6`](https://downloads.haskell.org/~ghc/9.6.6/docs/users_guide/9.6.6-notes.html), Stackage LTS `22.43`
+* Minimum required glibc version is bumped from [`2.28` to `2.31`](https://sourceware.org/glibc/wiki/Glibc%20Timeline)
diff --git a/CONTRIBUTORS.md b/CONTRIBUTORS.md
index aa5ddefd3f..cfbb98e362 100644
--- a/CONTRIBUTORS.md
+++ b/CONTRIBUTORS.md
@@ -16,6 +16,7 @@ If you would prefer to use different terms, please use the section below instead
 | :------- | :--- | :------ |
 | [@5outh](https://github.com/5outh) | Benjamin Kovach | [MIT license] |
 | [@actionshrimp](https://github.com/actionshrimp) | David Aitken | [MIT license] |
+| [@ad-si](https://github.com/ad-si) | Adrian Sieber | [MIT license] |
 | [@adnelson](https://github.com/adnelson) | Allen Nelson | [MIT license] |
 | [@alexbiehl](https://github.com/alexbiehl) | Alexander Biehl | [MIT license] |
 | [@andreypopp](https://github.com/andreypopp) | Andrey Popp | [MIT license] |
diff --git a/INSTALL.md b/INSTALL.md
index 0bccc516c7..03f7748636 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -4,12 +4,13 @@ If you are having difficulty installing the PureScript compiler, feel free to as
 
 ## Requirements
 
-The PureScript compiler is built using GHC 9.2.8, and should be able to run on any operating system supported by GHC 9.2.8. In particular:
+The PureScript compiler is built using GHC 9.6.6, and should be able to run on any operating system supported by GHC 9.6.6.
+In particular:
 
 * for Windows users, versions predating Vista are not officially supported,
 * for macOS / OS X users, versions predating Mac OS X 10.7 (Lion) are not officially supported.
 
-See also <https://www.haskell.org/ghc/download_ghc_9_2_8.html> for more details about the operating systems which GHC 9.2.8 supports.
+See also <https://www.haskell.org/ghc/download_ghc_9_6_6.html> for more details about the operating systems which GHC 9.6.6 supports.
 
 ## Official prebuilt binaries
 
diff --git a/LICENSE b/LICENSE
index 490ff3651c..713d3371a3 100644
--- a/LICENSE
+++ b/LICENSE
@@ -107,7 +107,6 @@ PureScript uses the following Haskell library packages. Their license files foll
   optparse-applicative
   parallel
   parsec
-  pattern-arrows
   pretty
   primitive
   process
@@ -3186,29 +3185,6 @@ parsec LICENSE file:
   negligence or otherwise) arising in any way out of the use of this software,
   even if advised of the possibility of such damage.
 
-pattern-arrows LICENSE file:
-
-  The MIT License (MIT)
-
-  Copyright (c) 2013 Phil Freeman
-
-  Permission is hereby granted, free of charge, to any person obtaining a copy of
-  this software and associated documentation files (the "Software"), to deal in
-  the Software without restriction, including without limitation the rights to
-  use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
-  the Software, and to permit persons to whom the Software is furnished to do so,
-  subject to the following conditions:
-
-  The above copyright notice and this permission notice shall be included in all
-  copies or substantial portions of the Software.
-
-  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
-  FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
-  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
-  IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
-  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-
 pretty LICENSE file:
 
   This library (libraries/pretty) is derived from code from
diff --git a/Makefile b/Makefile
index 53da1f3710..91235d9c8f 100644
--- a/Makefile
+++ b/Makefile
@@ -4,6 +4,7 @@ package = purescript
 exe_target = purs
 stack_yaml = STACK_YAML="stack.yaml"
 stack = $(stack_yaml) stack
+stack_dir = .stack-work
 
 .DEFAULT_GOAL := help
 
@@ -14,6 +15,10 @@ $(bin_dir)/hlint: ci/install-hlint.sh
 clean: ## Remove build artifacts
 	rm -fr $(bin_dir)
 	rm -fr $(build_dir)
+	rm -fr $(stack_dir)
+	rm -fr dist-newstyle
+	rm -fr .psci_modules
+	rm -fr .test_modules
 
 help: ## Print documentation
 	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}'
diff --git a/app/Command/Docs.hs b/app/Command/Docs.hs
index 987023c98c..22bd6bdd3f 100644
--- a/app/Command/Docs.hs
+++ b/app/Command/Docs.hs
@@ -15,7 +15,8 @@ import Language.PureScript.Docs qualified as D
 import Language.PureScript.Docs.Tags (dumpCtags, dumpEtags)
 import Language.PureScript.Glob (PSCGlobs(..), toInputGlobs, warnFileTypeNotFound)
 import Options.Applicative qualified as Opts
-import Text.PrettyPrint.ANSI.Leijen qualified as PP
+import Prettyprinter qualified as PP
+import Prettyprinter.Render.Terminal (AnsiStyle)
 import SharedCLI qualified
 import System.Directory (getCurrentDirectory, createDirectoryIfMissing, removeFile)
 import System.Exit (exitFailure)
@@ -113,10 +114,10 @@ defaultOutputForFormat fmt =
     Ctags -> "tags"
 
 pscDocsOptions :: Opts.Parser PSCDocsOptions
-pscDocsOptions = 
-  PSCDocsOptions <$> format 
-                 <*> output 
-                 <*> compileOutputDir 
+pscDocsOptions =
+  PSCDocsOptions <$> format
+                 <*> output
+                 <*> compileOutputDir
                  <*> many SharedCLI.inputFile
                  <*> SharedCLI.globInputFile
                  <*> many SharedCLI.excludeFiles
@@ -150,9 +151,9 @@ infoModList :: Opts.InfoMod a
 infoModList = Opts.fullDesc <> footerInfo where
   footerInfo = Opts.footerDoc $ Just examples
 
-examples :: PP.Doc
+examples :: PP.Doc AnsiStyle
 examples =
-  PP.vcat $ map PP.text
+  PP.vcat
     [ "Examples:"
     , "  write documentation for all modules to ./generated-docs:"
     , "    purs docs \"src/**/*.purs\" \".psc-package/*/*/*/src/**/*.purs\""
diff --git a/app/Main.hs b/app/Main.hs
index c925a4a313..ff4e04ab6d 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -13,9 +13,10 @@ import Command.REPL qualified as REPL
 import Control.Monad (join)
 import Data.Foldable (fold)
 import Options.Applicative qualified as Opts
+import Prettyprinter qualified as Doc
+import Prettyprinter.Render.Terminal (AnsiStyle)
 import System.Environment (getArgs)
 import System.IO qualified as IO
-import Text.PrettyPrint.ANSI.Leijen qualified as Doc
 import Version (versionString)
 
 
@@ -39,11 +40,11 @@ main = do
             "For example, `purs compile --help` displays options specific to the `compile` command."
         , Doc.hardline
         , Doc.hardline
-        , Doc.text $ "purs " ++ versionString
+        , Doc.pretty $ "purs " ++ versionString
         ]
 
-    para :: String -> Doc.Doc
-    para = foldr (Doc.</>) Doc.empty . map Doc.text . words
+    para :: String -> Doc.Doc AnsiStyle
+    para = foldr (\x y -> x <> Doc.softline <> y) mempty . map Doc.pretty . words
 
     -- | Displays full command help when invoked with no arguments.
     execParserPure :: Opts.ParserInfo a -> [String] -> Opts.ParserResult a
diff --git a/cabal.project b/cabal.project
index 51c7ecb87d..61c5c9bd35 100644
--- a/cabal.project
+++ b/cabal.project
@@ -1,2 +1,7 @@
 packages:
   purescript.cabal
+
+source-repository-package
+   type: git
+   location: https://github.com/purescript/cheapskate.git
+   tag: 8bfaf4beeb108e97a274ed51303f278905979e87
diff --git a/ci/build-package-set.sh b/ci/build-package-set.sh
index 12a6fcb34c..f11b556871 100755
--- a/ci/build-package-set.sh
+++ b/ci/build-package-set.sh
@@ -5,7 +5,7 @@ shopt -s nullglob
 
 psroot=$(dirname "$(dirname "$(realpath "$0")")")
 
-if [[ "${CI:-}" && "$(echo $psroot/CHANGELOG.d/breaking_*)" ]]; then
+if [[ "${CI:-}" && "$(echo "$psroot"/CHANGELOG.d/breaking_*)" ]]; then
   echo "Skipping package-set build due to unreleased breaking changes"
   exit 0
 fi
@@ -16,23 +16,17 @@ export PATH="$tmpdir/node_modules/.bin:$PATH"
 cd "$tmpdir"
 
 echo ::group::Ensure Spago is available
-which spago || npm install spago@0.20.8
+which spago || npm install spago@0.93.43
 echo ::endgroup::
 
 echo ::group::Create dummy project
-echo 'let upstream = https://github.com/purescript/package-sets/releases/download/XXX/packages.dhall in upstream' > packages.dhall
-echo '{ name = "my-project", dependencies = [] : List Text, packages = ./packages.dhall, sources = [] : List Text }' > spago.dhall
-spago upgrade-set
-# Override the `metadata` package's version to match `purs` version
-# so that `spago build` actually works
-sed -i'' "\$c in upstream with metadata.version = \"v$(purs --version | { read v z && echo $v; })\"" packages.dhall
-spago install $(spago ls packages | while read name z; do if [[ $name != metadata ]]; then echo $name; fi; done)
+spago init --name purescript-dummy
 echo ::endgroup::
 
 echo ::group::Compile package set
-spago build
+spago ls packages --json | jq -r 'keys[]' | xargs spago install
 echo ::endgroup::
 
 echo ::group::Document package set
-spago docs --no-search
+spago docs
 echo ::endgroup::
diff --git a/purescript.cabal b/purescript.cabal
index 0d32ce4814..93b02ebbc9 100644
--- a/purescript.cabal
+++ b/purescript.cabal
@@ -153,18 +153,17 @@ common defaults
     -- modules must be parseable by this library otherwise the compiler
     -- will reject them. It should therefore always be pinned to a single
     -- specific version.
-    aeson >=2.0.3.0 && <2.1,
-    aeson-better-errors >=0.9.1.1 && <0.10,
-    ansi-terminal >=0.11.3 && <0.12,
+    aeson >=2.0.3.0 && <2.2,
+    aeson-better-errors >=0.9.1.3 && <0.10,
+    ansi-terminal >=0.11.3 && <1.1,
     array >=0.5.4.0 && <0.6,
-    base >=4.16.2.0 && <4.17,
+    base >=4.16.2.0 && <4.19,
     blaze-html >=0.9.1.2 && <0.10,
     bower-json >=1.1.0.0 && <1.2,
     boxes >=0.1.5 && <0.2,
     bytestring >=0.11.3.1 && <0.12,
-    Cabal >=3.6.3.0 && <3.7,
+    Cabal >=3.10.3.0 && <3.11,
     cborg >=0.2.7.0 && <0.3,
-    serialise >=0.2.5.0 && <0.3,
     cheapskate >=0.1.1.2 && <0.2,
     clock >=0.8.3 && <0.9,
     containers >=0.6.5.1 && <0.7,
@@ -177,38 +176,38 @@ common defaults
     file-embed >=0.0.15.0 && <0.1,
     filepath >=1.4.2.2 && <1.5,
     Glob >=0.10.2 && <0.11,
-    haskeline >=0.8.2 && <0.9,
+    haskeline ==0.8.2,
     language-javascript ==0.7.0.0,
-    lens >=5.1.1 && <5.2,
+    lens >=5.1.1 && <5.3,
     lifted-async >=0.10.2.2 && <0.11,
     lifted-base >=0.2.3.12 && <0.3,
-    memory >=0.17.0 && <0.18,
+    memory >=0.17.0 && <0.19,
     monad-control >=1.0.3.1 && <1.1,
     monad-logger >=0.3.36 && <0.4,
     monoidal-containers >=0.6.2.0 && <0.7,
-    mtl >=2.2.2 && <2.3,
+    mtl >=2.2.2 && <2.4,
     parallel >=3.2.2.0 && <3.3,
     parsec >=3.1.15.0 && <3.2,
-    pattern-arrows >=0.0.2 && <0.1,
-    process ==1.6.13.1,
+    process >=1.6.19.0 && <1.7,
     protolude >=0.3.1 && <0.4,
     regex-tdfa >=1.3.1.2 && <1.4,
     safe >=0.3.19 && <0.4,
     scientific >=0.3.7.0 && <0.4,
+    semialign >=1.2.0.1 && <1.4,
     semigroups ==0.20.*,
-    semialign >=1.2.0.1 && <1.3,
+    serialise >=0.2.5.0 && <0.3,
     sourcemap >=0.1.7 && <0.2,
     stm >=2.5.0.2 && <2.6,
     stringsearch >=0.3.6.6 && <0.4,
-    template-haskell >=2.18.0.0 && <2.19,
-    text >=1.2.5.0 && <1.3,
-    these >=1.1.1.1 && <1.2,
-    time >=1.11.1.1 && <1.12,
-    transformers >=0.5.6.2 && <0.6,
+    template-haskell >=2.18.0.0 && <2.21,
+    text >=1.2.5.0 && <2.1,
+    these >=1.1.1.1 && <1.3,
+    time >=1.11.1.1 && <1.13,
+    transformers >=0.5.6.2 && <0.7,
     transformers-base >=0.4.6 && <0.5,
     utf8-string >=1.0.2 && <1.1,
-    vector >=0.12.3.1 && <0.13,
-    witherable >=0.4.2 && <0.5
+    vector >=0.12.3.1 && <0.14,
+    witherable >=0.4.2 && <0.5,
 
 library
   import: defaults
@@ -217,6 +216,7 @@ library
     Control.Monad.Logger
     Control.Monad.Supply
     Control.Monad.Supply.Class
+    Control.PatternArrows
     Language.PureScript
     Language.PureScript.AST
     Language.PureScript.AST.Binders
@@ -403,10 +403,11 @@ executable purs
   main-is: Main.hs
   ghc-options: -fno-warn-unused-do-bind -threaded -rtsopts -with-rtsopts=-N -Wno-unused-packages
   build-depends:
-    ansi-wl-pprint >=0.6.9 && <0.7,
+    prettyprinter >=1.6 && <1.8,
+    prettyprinter-ansi-terminal >=1.1.1 && <1.2,
     exceptions >=0.10.4 && <0.11,
     network >=3.1.2.7 && <3.2,
-    optparse-applicative >=0.17.0.0 && <0.18,
+    optparse-applicative >=0.17.0.0 && <0.19,
     purescript
   if flag(release)
     cpp-options: -DRELEASE
@@ -440,7 +441,7 @@ test-suite tests
   build-depends:
     purescript,
     generic-random >=1.5.0.1 && <1.6,
-    hspec >= 2.10.7 && < 3,
+    hspec >= 2.11.10 && < 3,
     HUnit >=1.6.2.0 && <1.7,
     newtype >=0.2.2.0 && <0.3,
     QuickCheck >=2.14.2 && <2.15,
diff --git a/src/Control/Monad/Supply/Class.hs b/src/Control/Monad/Supply/Class.hs
index e8656f0c69..b10b42d549 100644
--- a/src/Control/Monad/Supply/Class.hs
+++ b/src/Control/Monad/Supply/Class.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE TypeOperators #-}
+
 -- |
 -- A class for monads supporting a supply of fresh names
 --
diff --git a/src/Control/PatternArrows.hs b/src/Control/PatternArrows.hs
new file mode 100644
index 0000000000..b01d1cccdc
--- /dev/null
+++ b/src/Control/PatternArrows.hs
@@ -0,0 +1,118 @@
+-----------------------------------------------------------------------------
+--
+-- Module      :  Control.PatternArrows
+-- Copyright   :  (c) Phil Freeman 2013
+-- License     :  MIT
+--
+-- Maintainer  :  Phil Freeman <paf31@cantab.net>
+-- Stability   :  experimental
+-- Portability :
+--
+-- |
+-- Arrows for Pretty Printing
+--
+-----------------------------------------------------------------------------
+
+{-# LANGUAGE GeneralizedNewtypeDeriving, GADTs #-}
+
+module Control.PatternArrows where
+
+import Prelude
+
+import Control.Arrow ((***), (<+>))
+import Control.Arrow qualified as A
+import Control.Category ((>>>))
+import Control.Category qualified as C
+import Control.Monad.State
+import Control.Monad.Fix (fix)
+
+-- |
+-- A first-order pattern match
+--
+-- A pattern is a Kleisli arrow for the @StateT Maybe@ monad. That is, patterns can fail, and can carry user-defined state.
+--
+newtype Pattern u a b = Pattern { runPattern :: A.Kleisli (StateT u Maybe) a b } deriving (A.Arrow, A.ArrowZero, A.ArrowPlus)
+
+instance C.Category (Pattern u) where
+    id = Pattern C.id
+    Pattern p1 . Pattern p2 = Pattern (p1 C.. p2)
+
+instance Functor (Pattern u a) where
+  fmap f (Pattern p) = Pattern $ A.Kleisli $ fmap f . A.runKleisli p
+
+-- |
+-- Run a pattern with an input and initial user state
+--
+-- Returns Nothing if the pattern fails to match
+--
+pattern_ :: Pattern u a b -> u -> a -> Maybe b
+pattern_ p u = flip evalStateT u . A.runKleisli (runPattern p)
+
+-- |
+-- Construct a pattern from a function
+--
+mkPattern :: (a -> Maybe b) -> Pattern u a b
+mkPattern f = Pattern $ A.Kleisli (lift . f)
+
+-- |
+-- Construct a pattern from a stateful function
+--
+mkPattern' :: (a -> StateT u Maybe b) -> Pattern u a b
+mkPattern' = Pattern . A.Kleisli
+
+-- |
+-- Construct a pattern which recursively matches on the left-hand-side
+--
+chainl :: Pattern u a (a, a) -> (r -> r -> r) -> Pattern u a r -> Pattern u a r
+chainl g f p = fix $ \c -> g >>> ((c <+> p) *** p) >>> A.arr (uncurry f)
+
+-- |
+-- Construct a pattern which recursively matches on the right-hand side
+--
+chainr :: Pattern u a (a, a) -> (r -> r -> r) -> Pattern u a r -> Pattern u a r
+chainr g f p = fix $ \c -> g >>> (p *** (c <+> p)) >>> A.arr (uncurry f)
+
+-- |
+-- Construct a pattern which recursively matches on one-side of a tuple
+--
+wrap :: Pattern u a (s, a) -> (s -> r -> r) -> Pattern u a r -> Pattern u a r
+wrap g f p = fix $ \c -> g >>> (C.id *** (c <+> p)) >>> A.arr (uncurry f)
+
+-- |
+-- Construct a pattern which matches a part of a tuple
+--
+split :: Pattern u a (s, t) -> (s -> t -> r) -> Pattern u a r
+split s f = s >>> A.arr (uncurry f)
+
+-- |
+-- A table of operators
+--
+data OperatorTable u a r = OperatorTable { runOperatorTable :: [ [Operator u a r] ] }
+
+-- |
+-- An operator:
+--
+--  [@AssocL@] A left-associative operator
+--
+--  [@AssocR@] A right-associative operator
+--
+--  [@Wrap@] A prefix-like or postfix-like operator
+--
+--  [@Split@] A prefix-like or postfix-like operator which does not recurse into its operand
+--
+data Operator u a r where
+  AssocL :: Pattern u a (a, a) -> (r -> r -> r) -> Operator u a r
+  AssocR :: Pattern u a (a, a) -> (r -> r -> r) -> Operator u a r
+  Wrap   :: Pattern u a (s, a) -> (s -> r -> r) -> Operator u a r
+  Split  :: Pattern u a (s, t) -> (s -> t -> r) -> Operator u a r
+
+-- |
+-- Build a pretty printer from an operator table and an indecomposable pattern
+--
+buildPrettyPrinter :: OperatorTable u a r -> Pattern u a r -> Pattern u a r
+buildPrettyPrinter table p = foldl (\p' ops -> foldl1 (<+>) (flip map ops $ \case
+    AssocL pat g -> chainl pat g p'
+    AssocR pat g -> chainr pat g p'
+    Wrap pat g -> wrap pat g p'
+    Split pat g -> split pat g
+  ) <+> p') p $ runOperatorTable table
diff --git a/src/Language/PureScript/CodeGen/JS.hs b/src/Language/PureScript/CodeGen/JS.hs
index 14d122a37d..3a4e371187 100644
--- a/src/Language/PureScript/CodeGen/JS.hs
+++ b/src/Language/PureScript/CodeGen/JS.hs
@@ -9,7 +9,6 @@ module Language.PureScript.CodeGen.JS
 import Prelude
 import Protolude (ordNub)
 
-import Control.Applicative (liftA2)
 import Control.Monad (forM, replicateM, void)
 import Control.Monad.Except (MonadError, throwError)
 import Control.Monad.Reader (MonadReader, asks)
diff --git a/src/Language/PureScript/CoreImp/Optimizer/TCO.hs b/src/Language/PureScript/CoreImp/Optimizer/TCO.hs
index 34746ae3db..a1d4a47c2b 100644
--- a/src/Language/PureScript/CoreImp/Optimizer/TCO.hs
+++ b/src/Language/PureScript/CoreImp/Optimizer/TCO.hs
@@ -3,7 +3,7 @@ module Language.PureScript.CoreImp.Optimizer.TCO (tco) where
 
 import Prelude
 
-import Control.Applicative (empty, liftA2)
+import Control.Applicative (empty)
 import Control.Monad (guard)
 import Control.Monad.State (State, evalState, get, modify)
 import Data.Functor (($>), (<&>))
diff --git a/src/Language/PureScript/Docs/RenderedCode/RenderType.hs b/src/Language/PureScript/Docs/RenderedCode/RenderType.hs
index a082b4b833..c6a985b09b 100644
--- a/src/Language/PureScript/Docs/RenderedCode/RenderType.hs
+++ b/src/Language/PureScript/Docs/RenderedCode/RenderType.hs
@@ -233,7 +233,7 @@ renderTypeWithRole = \case
 renderType' :: PrettyPrintType -> RenderedCode
 renderType'
   = fromMaybe (internalError "Incomplete pattern")
-  . PA.pattern matchType ()
+  . PA.pattern_ matchType ()
 
 renderTypeVars :: [(TypeVarVisibility, Text, Maybe PrettyPrintType)] -> RenderedCode
 renderTypeVars tyVars = mintersperse sp (map renderTypeVar tyVars)
@@ -252,4 +252,4 @@ renderTypeAtom = renderTypeAtom' . convertPrettyPrintType maxBound
 renderTypeAtom' :: PrettyPrintType -> RenderedCode
 renderTypeAtom'
   = fromMaybe (internalError "Incomplete pattern")
-  . PA.pattern matchTypeAtom ()
+  . PA.pattern_ matchTypeAtom ()
diff --git a/src/Language/PureScript/Linter/Exhaustive.hs b/src/Language/PureScript/Linter/Exhaustive.hs
index 697fefe8a0..eb03da41e0 100644
--- a/src/Language/PureScript/Linter/Exhaustive.hs
+++ b/src/Language/PureScript/Linter/Exhaustive.hs
@@ -11,7 +11,6 @@ module Language.PureScript.Linter.Exhaustive
 import Prelude
 import Protolude (ordNub)
 
-import Control.Applicative (Applicative(..))
 import Control.Arrow (first, second)
 import Control.Monad (unless)
 import Control.Monad.Writer.Class (MonadWriter(..))
diff --git a/src/Language/PureScript/Pretty/Types.hs b/src/Language/PureScript/Pretty/Types.hs
index 20de0ed9e2..9b3be46937 100644
--- a/src/Language/PureScript/Pretty/Types.hs
+++ b/src/Language/PureScript/Pretty/Types.hs
@@ -238,7 +238,7 @@ forall_ = mkPattern match
 typeAtomAsBox' :: PrettyPrintType -> Box
 typeAtomAsBox'
   = fromMaybe (internalError "Incomplete pattern")
-  . PA.pattern (matchTypeAtom defaultOptions) ()
+  . PA.pattern_ (matchTypeAtom defaultOptions) ()
 
 typeAtomAsBox :: Int -> Type a -> Box
 typeAtomAsBox maxDepth = typeAtomAsBox' . convertPrettyPrintType maxDepth
@@ -280,7 +280,7 @@ unicodeOptions = TypeRenderOptions False True False
 typeAsBoxImpl :: TypeRenderOptions -> PrettyPrintType -> Box
 typeAsBoxImpl tro
   = fromMaybe (internalError "Incomplete pattern")
-  . PA.pattern (matchType tro) ()
+  . PA.pattern_ (matchType tro) ()
 
 -- | Generate a pretty-printed string representing a 'Type'
 prettyPrintType :: Int -> Type a -> String
diff --git a/src/Language/PureScript/Sugar/BindingGroups.hs b/src/Language/PureScript/Sugar/BindingGroups.hs
index d2f9aebf2b..835e775f81 100644
--- a/src/Language/PureScript/Sugar/BindingGroups.hs
+++ b/src/Language/PureScript/Sugar/BindingGroups.hs
@@ -114,8 +114,8 @@ createBindingGroups moduleName = mapM f <=< handleDecls
 
       valueDeclarationInfo = M.fromList $ swap <$> valueDeclarationKeys
       findDeclarationInfo i = (M.findWithDefault False i valueDeclarationInfo, i)
-      computeValueDependencies = (`intersect` valueDeclarationKeys) . fmap findDeclarationInfo . usedIdents moduleName 
-  
+      computeValueDependencies = (`intersect` valueDeclarationKeys) . fmap findDeclarationInfo . usedIdents moduleName
+
       makeValueDeclarationVert = (,,) <$> id <*> makeValueDeclarationKey <*> computeValueDependencies
       valueDeclarationVerts = makeValueDeclarationVert <$> values
 
@@ -267,7 +267,7 @@ toDataBindingGroup
   -> m Declaration
 toDataBindingGroup (AcyclicSCC (d, _, _)) = return d
 toDataBindingGroup (CyclicSCC ds')
-  | Just kds@((ss, _):|_) <- nonEmpty $ concatMap (kindDecl . getDecl) ds' = throwError . errorMessage' ss . CycleInKindDeclaration $ fmap snd kds
+  | Just kds@((ss, _) :| _) <- nonEmpty $ concatMap (kindDecl . getDecl) ds' = throwError . errorMessage' ss . CycleInKindDeclaration $ fmap snd kds
   | not (null typeSynonymCycles) =
       throwError
         . MultipleErrors
diff --git a/src/Language/PureScript/TypeChecker/Monad.hs b/src/Language/PureScript/TypeChecker/Monad.hs
index b6382e6707..b33127200d 100644
--- a/src/Language/PureScript/TypeChecker/Monad.hs
+++ b/src/Language/PureScript/TypeChecker/Monad.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE GADTs #-}
+{-# LANGUAGE TypeOperators #-}
 
 -- |
 -- Monads for type checking and type inference and associated data types
diff --git a/src/Language/PureScript/TypeChecker/Synonyms.hs b/src/Language/PureScript/TypeChecker/Synonyms.hs
index 567ae415ef..8d2cf7886c 100644
--- a/src/Language/PureScript/TypeChecker/Synonyms.hs
+++ b/src/Language/PureScript/TypeChecker/Synonyms.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE GADTs #-}
+{-# LANGUAGE TypeOperators #-}
 
 -- |
 -- Functions for replacing fully applied type synonyms
diff --git a/stack.yaml b/stack.yaml
index 88b27b1a46..afbac89bca 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,6 +1,6 @@
 # Please update Haskell image versions under .github/workflows/ci.yml together to use the same GHC version
 # (or the CI build will fail)
-resolver: lts-20.26
+resolver: lts-22.43
 pvp-bounds: both
 packages:
 - '.'
@@ -13,20 +13,14 @@ extra-deps:
 # `async` to be used as an object key:
 # https://github.com/erikd/language-javascript/issues/131
 - language-javascript-0.7.0.0
-# Fix issue with libtinfo.
-# See https://github.com/purescript/purescript/issues/4253
-- process-1.6.13.1
-# The Cabal library is not in Stackage
-- Cabal-3.6.3.0
-# hspec versions 2.9.3 to 2.10.6 depend on ghc
-# ghc depends on terminfo by default, but that can be ignored
-# if one uses the '-terminfo' flag.
-# Unfortunately, hspec doesn't expose a similar flag.
-#
-# Using hspec >= 2.10.7 addresses this.
-- hspec-2.10.9
-- hspec-core-2.10.9
-- hspec-discover-2.10.9
+- bower-json-1.1.0.0
+- haskeline-0.8.2
+- these-1.2.1
+- aeson-better-errors-0.9.1.3
+
+- github: purescript/cheapskate
+  commit: 8bfaf4beeb108e97a274ed51303f278905979e87
+
 nix:
   packages:
   - zlib
@@ -37,8 +31,10 @@ nix:
 flags:
   aeson-pretty:
     lib-only: true
-  these:
-    assoc: false
   haskeline:
     # Avoids a libtinfo dynamic library dependency
     terminfo: false
+
+allow-newer: true
+allow-newer-deps:
+- haskeline
diff --git a/stack.yaml.lock b/stack.yaml.lock
new file mode 100644
index 0000000000..0af2cebb41
--- /dev/null
+++ b/stack.yaml.lock
@@ -0,0 +1,58 @@
+# This file was autogenerated by Stack.
+# You should not edit this file by hand.
+# For more information, please see the documentation at:
+#   https://docs.haskellstack.org/en/stable/topics/lock_files
+
+packages:
+- completed:
+    hackage: language-javascript-0.7.0.0@sha256:3eab0262b8ac5621936a4beab6a0f97d0e00a63455a8b0e3ac1547b4088dae7d,3898
+    pantry-tree:
+      sha256: b0f28d836cb3fbde203fd7318a896c3a20acd8653a905e1950ae2d9a64bccebf
+      size: 2244
+  original:
+    hackage: language-javascript-0.7.0.0
+- completed:
+    hackage: bower-json-1.1.0.0@sha256:a136aaca67bf0d15c336f5864f7e9d40ebe046ca2cb4b25bc4895617ea35f9f6,1864
+    pantry-tree:
+      sha256: 3acd48e7012f246ad44c7c17cd6340362b1dc448c1d93156280814e76d9e0589
+      size: 419
+  original:
+    hackage: bower-json-1.1.0.0
+- completed:
+    hackage: haskeline-0.8.2@sha256:3b4b594095d64f5fa199b07bdca7d6b790313ed7f380a1b061845507e6563880,6005
+    pantry-tree:
+      sha256: 17ee6b093c5135399b8e6bc3a63d9c6a4b0bc2100b495d2d974bc1464769de39
+      size: 2955
+  original:
+    hackage: haskeline-0.8.2
+- completed:
+    hackage: these-1.2.1@sha256:35c57aede96c15ea1fed559ac287b1168eb2b2869d79e62ed8c845780b7ea136,2294
+    pantry-tree:
+      sha256: dc6366ac715dfdf5338a615f71b9ed0542c403a6afcbedcddbc879e947aea6b3
+      size: 351
+  original:
+    hackage: these-1.2.1
+- completed:
+    hackage: aeson-better-errors-0.9.1.3@sha256:1bfdda3982368cafc7317b9f0c1f7267a6b0bbac9515ae1fad37f2b19178f567,2071
+    pantry-tree:
+      sha256: 1c14247866dfb8052506c179e4725b8a7ce1472a4fb227d61576d862d9494551
+      size: 492
+  original:
+    hackage: aeson-better-errors-0.9.1.3
+- completed:
+    name: cheapskate
+    pantry-tree:
+      sha256: a2253619f50d26f0137a802e51e5e7103ee52b1f71bc060d93a0979dcbefa2c8
+      size: 12069
+    sha256: 959fc7a6ca7e0a743b06b0c287aa4a1c3ec7fc740e5830a4a841d43e925a6d73
+    size: 62502
+    url: https://github.com/purescript/cheapskate/archive/8bfaf4beeb108e97a274ed51303f278905979e87.tar.gz
+    version: 0.1.1.2
+  original:
+    url: https://github.com/purescript/cheapskate/archive/8bfaf4beeb108e97a274ed51303f278905979e87.tar.gz
+snapshots:
+- completed:
+    sha256: 08bd13ce621b41a8f5e51456b38d5b46d7783ce114a50ab604d6bbab0d002146
+    size: 720271
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/22/43.yaml
+  original: lts-22.43
diff --git a/update-changelog.hs b/update-changelog.hs
index b9296440d4..291160ceca 100755
--- a/update-changelog.hs
+++ b/update-changelog.hs
@@ -25,7 +25,8 @@
   , RecordWildCards
   , TupleSections
   , ViewPatterns
-#-}
+ #-} -- Hlint requires this leading space
+
 -- |
 -- This script updates CHANGELOG.md with the contents of CHANGELOG.d, and
 -- empties CHANGELOG.d. It takes care of:
diff --git a/weeder.dhall b/weeder.dhall
deleted file mode 100644
index 95686c45e8..0000000000
--- a/weeder.dhall
+++ /dev/null
@@ -1,41 +0,0 @@
-{ roots =
-  [ "^Main\\.main$"
-  , "^PscIdeSpec\\.main$"
-
-  -- These declarations are used in Pursuit. (The Types declarations are
-  -- reexported in the L.P.Docs module, and referenced from there, but Weeder
-  -- isn't that smart.)
-  , "^Language\\.PureScript\\.Docs\\.AsHtml\\.packageAsHtml$"
-  , "^Language\\.PureScript\\.Docs\\.Types\\.asUploadedPackage$"
-  , "^Language\\.PureScript\\.Docs\\.Types\\.getLink$"
-  , "^Language\\.PureScript\\.Docs\\.Types\\.getLinksContext$"
-  , "^Language\\.PureScript\\.Docs\\.Types\\.packageName$"
-  , "^Language\\.PureScript\\.Docs\\.Types\\.verifyPackage$"
-
-  -- These declarations are believed to be used in other projects that we want
-  -- to continue to support.
-  , "^Language\\.PureScript\\.CoreFn\\.FromJSON\\.moduleFromJSON$"
-  , "^Language\\.PureScript\\.CST\\.Print\\.printModule$"
-
-  -- These declarations are there to be used during development or testing.
-  , "^Language\\.PureScript\\.Ide\\.Imports\\.parseImport$"
-  , "^Language\\.PureScript\\.TypeChecker\\.Monad\\.debug"
-
-  -- These declarations are used by Template Haskell code.
-  , "^Language\\.PureScript\\.Constants\\.TH\\."
-
-  -- These declarations are produced by Template Haskell when generating
-  -- pattern synonyms; this confuses Weeder.
-  , "^Language\\.PureScript\\.Constants\\..*\\.\\$[bm]"
-
-  -- These declarations are unprincipled exceptions that we don't mind
-  -- supporting just in case they're used now or in the future.
-  , "^Language\\.PureScript\\.CST\\.Parser\\.parseExpr$"
-
-  -- These declarations are generated by tools; it doesn't matter if they're
-  -- unused because we can't do anything about them.
-  , "^Language\\.PureScript\\.CST\\.Parser\\.happy"
-  , "^Paths_purescript?\\."
-  ]
-, type-class-roots = True
-}
diff --git a/weeder.toml b/weeder.toml
new file mode 100644
index 0000000000..1a8249a2e2
--- /dev/null
+++ b/weeder.toml
@@ -0,0 +1,40 @@
+roots = [
+  "^Main\\.main$",
+  "^PscIdeSpec\\.main$",
+
+  # These declarations are used in Pursuit. (The Types declarations are
+  # reexported in the L.P.Docs module, and referenced from there, but Weeder
+  # isn't that smart.)
+  "^Language\\.PureScript\\.Docs\\.AsHtml\\.packageAsHtml$",
+  "^Language\\.PureScript\\.Docs\\.Types\\.asUploadedPackage$",
+  "^Language\\.PureScript\\.Docs\\.Types\\.getLink$",
+  "^Language\\.PureScript\\.Docs\\.Types\\.getLinksContext$",
+  "^Language\\.PureScript\\.Docs\\.Types\\.packageName$",
+  "^Language\\.PureScript\\.Docs\\.Types\\.verifyPackage$",
+
+  # These declarations are believed to be used in other projects that we want
+  # to continue to support.
+  "^Language\\.PureScript\\.CoreFn\\.FromJSON\\.moduleFromJSON$",
+  "^Language\\.PureScript\\.CST\\.Print\\.printModule$",
+
+  # These declarations are there to be used during development or testing.
+  "^Language\\.PureScript\\.Ide\\.Imports\\.parseImport$",
+  "^Language\\.PureScript\\.TypeChecker\\.Monad\\.debug",
+
+  # These declarations are used by Template Haskell code.
+  "^Language\\.PureScript\\.Constants\\.TH\\.",
+
+  # These declarations are produced by Template Haskell when generating
+  # pattern synonyms; this confuses Weeder.
+  "^Language\\.PureScript\\.Constants\\..*\\.\\$[bm]",
+
+  # These declarations are unprincipled exceptions that we don't mind
+  # supporting just in case they're used now or in the future.
+  "^Language\\.PureScript\\.CST\\.Parser\\.parseExpr$",
+
+  # These declarations are generated by tools; it doesn't matter if they're
+  # unused because we can't do anything about them.
+  "^Language\\.PureScript\\.CST\\.Parser\\.happy",
+  "^Paths_purescript?\\.",
+]
+type-class-roots = true

From 3b843f2c6a703b76274e2a1f03e7b9cf414b7cbb Mon Sep 17 00:00:00 2001
From: Justin Garcia <purefunctor@gmail.com>
Date: Wed, 31 Jul 2024 01:48:50 +0800
Subject: [PATCH 2/4] Implement the focus command for limiting externs

---
 src/Language/PureScript/Ide.hs         | 17 +++++++++---
 src/Language/PureScript/Ide/Command.hs |  9 +++++++
 src/Language/PureScript/Ide/State.hs   | 36 ++++++++++++++++++++++++++
 src/Language/PureScript/Ide/Types.hs   |  9 ++++++-
 4 files changed, 67 insertions(+), 4 deletions(-)

diff --git a/src/Language/PureScript/Ide.hs b/src/Language/PureScript/Ide.hs
index 57601c3d45..e0ecc4a8f7 100644
--- a/src/Language/PureScript/Ide.hs
+++ b/src/Language/PureScript/Ide.hs
@@ -22,6 +22,7 @@ import Protolude hiding (moduleName)
 
 import "monad-logger" Control.Monad.Logger (MonadLogger, logWarnN)
 import Data.Map qualified as Map
+import Data.Set qualified as Set
 import Data.Text qualified as T
 import Language.PureScript qualified as P
 import Language.PureScript.Glob (toInputGlobs, PSCGlobs(..))
@@ -37,7 +38,7 @@ import Language.PureScript.Ide.Matcher (Matcher)
 import Language.PureScript.Ide.Prim (idePrimDeclarations)
 import Language.PureScript.Ide.Rebuild (rebuildFileAsync, rebuildFileSync)
 import Language.PureScript.Ide.SourceFile (parseModulesFromFiles)
-import Language.PureScript.Ide.State (getAllModules, getLoadedModulenames, insertExterns, insertModule, populateVolatileState, populateVolatileStateSync, resetIdeState)
+import Language.PureScript.Ide.State (getAllModules, getLoadedModulenames, insertExterns, insertModule, populateVolatileState, populateVolatileStateSync, resetIdeState, setFocusedModules, getFocusedModules)
 import Language.PureScript.Ide.Types (Annotation(..), Ide, IdeConfiguration(..), IdeDeclarationAnn(..), IdeEnvironment(..), Success(..))
 import Language.PureScript.Ide.Util (discardAnn, identifierFromIdeDeclaration, namespaceForDeclaration, withEmptyAnn)
 import Language.PureScript.Ide.Usage (findUsages)
@@ -102,6 +103,8 @@ handleCommand c = case c of
     rebuildFileAsync file actualFile targets
   RebuildSync file actualFile targets ->
     rebuildFileSync file actualFile targets
+  Focus modulesToFocus ->
+    setFocusedModules modulesToFocus $> TextResult "Focused modules have been set."
   Cwd ->
     TextResult . T.pack <$> liftIO getCurrentDirectory
   Reset ->
@@ -215,10 +218,18 @@ loadModules
   => [P.ModuleName]
   -> m Success
 loadModules moduleNames = do
+  focusedModules <- getFocusedModules
   -- We resolve all the modulenames to externs files and load these into memory.
   oDir <- outputDirectory
-  let efPaths =
-        map (\mn -> oDir </> toS (P.runModuleName mn) </> P.externsFileName) moduleNames
+  let
+    -- But we only load the externs files that are in the focusedModules.
+    efModules = 
+        if Set.null focusedModules then 
+          moduleNames
+        else 
+          Set.toList $ Set.fromList moduleNames `Set.intersection` focusedModules
+    efPaths =
+        map (\mn -> oDir </> toS (P.runModuleName mn) </> P.externsFileName) efModules
   efiles <- traverse readExternFile efPaths
   traverse_ insertExterns efiles
 
diff --git a/src/Language/PureScript/Ide/Command.hs b/src/Language/PureScript/Ide/Command.hs
index ae4b6c9d8e..49e99a4474 100644
--- a/src/Language/PureScript/Ide/Command.hs
+++ b/src/Language/PureScript/Ide/Command.hs
@@ -62,6 +62,7 @@ data Command
     | List { listType :: ListType }
     | Rebuild FilePath (Maybe FilePath) (Set P.CodegenTarget)
     | RebuildSync FilePath (Maybe FilePath) (Set P.CodegenTarget)
+    | Focus [P.ModuleName]
     | Cwd
     | Reset
     | Quit
@@ -79,6 +80,7 @@ commandName c = case c of
   List{} -> "List"
   Rebuild{} -> "Rebuild"
   RebuildSync{} -> "RebuildSync"
+  Focus{} -> "Focus"
   Cwd{} -> "Cwd"
   Reset{} -> "Reset"
   Quit{} -> "Quit"
@@ -176,6 +178,13 @@ instance FromJSON Command where
           <$> params .: "file"
           <*> params .:? "actualFile"
           <*> (parseCodegenTargets =<< params .:? "codegen" .!= [ "js" ])
+      "focus" -> do
+        params' <- o .:? "params"
+        case params' of
+          Nothing -> 
+            pure (Focus [])
+          Just params ->
+            Focus <$> (map P.moduleNameFromString <$> params .:? "modules" .!= [])
       c -> fail ("Unknown command: " <> show c)
     where
       parseCodegenTargets ts =
diff --git a/src/Language/PureScript/Ide/State.hs b/src/Language/PureScript/Ide/State.hs
index 32478d7000..02481b305a 100644
--- a/src/Language/PureScript/Ide/State.hs
+++ b/src/Language/PureScript/Ide/State.hs
@@ -31,6 +31,9 @@ module Language.PureScript.Ide.State
   , populateVolatileStateSTM
   , getOutputDirectory
   , updateCacheTimestamp
+  , getFocusedModules
+  , setFocusedModules
+  , setFocusedModulesSTM
   -- for tests
   , resolveOperatorsForModule
   , resolveInstances
@@ -44,6 +47,7 @@ import Control.Lens (Ixed(..), preview, view, (%~), (.~), (^.))
 import "monad-logger" Control.Monad.Logger (MonadLogger, logWarnN)
 import Data.IORef (readIORef, writeIORef)
 import Data.Map.Lazy qualified as Map
+import Data.Set qualified as Set
 import Data.Time.Clock (UTCTime)
 import Data.Zip (unzip)
 import Language.PureScript qualified as P
@@ -141,6 +145,23 @@ setVolatileStateSTM ref vs = do
     x {ideVolatileState = vs}
   pure ()
 
+-- | Retrieves the ModifierState from the State.
+getModifierState :: Ide m => m IdeModifierState
+getModifierState = do
+  st <- ideStateVar <$> ask
+  liftIO (atomically (getModifierStateSTM st))
+
+-- | STM version of getModifierState
+getModifierStateSTM :: TVar IdeState -> STM IdeModifierState
+getModifierStateSTM ref = ideModifierState <$> readTVar ref
+
+-- | Sets the ModifierState inside Ide's state
+setModifierStateSTM :: TVar IdeState -> IdeModifierState -> STM ()
+setModifierStateSTM ref md = do
+  modifyTVar ref $ \x ->
+    x {ideModifierState = md}
+  pure ()
+
 -- | Checks if the given ModuleName matches the last rebuild cache and if it
 -- does returns all loaded definitions + the definitions inside the rebuild
 -- cache
@@ -447,3 +468,18 @@ resolveDataConstructorsForModule decls =
       & mapMaybe (preview (idaDeclaration . _IdeDeclDataConstructor))
       & foldr (\(IdeDataConstructor name typeName type') ->
                   Map.insertWith (<>) typeName [(name, type')]) Map.empty
+
+getFocusedModules :: Ide m => m (Set P.ModuleName)
+getFocusedModules = do
+  IdeModifierState{mdFocusedModules = focusedModules} <- getModifierState
+  pure focusedModules
+
+setFocusedModules :: Ide m => [P.ModuleName] -> m ()
+setFocusedModules modulesToFocus = do
+  st <- ideStateVar <$> ask
+  liftIO (atomically (setFocusedModulesSTM st modulesToFocus)) 
+
+setFocusedModulesSTM :: TVar IdeState -> [P.ModuleName] -> STM ()
+setFocusedModulesSTM ref modulesToFocus = do
+  IdeModifierState{} <- getModifierStateSTM ref
+  setModifierStateSTM ref (IdeModifierState (Set.fromList modulesToFocus))
diff --git a/src/Language/PureScript/Ide/Types.hs b/src/Language/PureScript/Ide/Types.hs
index 41532a3c51..8f8e84e18a 100644
--- a/src/Language/PureScript/Ide/Types.hs
+++ b/src/Language/PureScript/Ide/Types.hs
@@ -178,10 +178,11 @@ type Ide m = (MonadIO m, MonadReader IdeEnvironment m)
 data IdeState = IdeState
   { ideFileState :: IdeFileState
   , ideVolatileState :: IdeVolatileState
+  , ideModifierState :: IdeModifierState
   } deriving (Show)
 
 emptyIdeState :: IdeState
-emptyIdeState = IdeState emptyFileState emptyVolatileState
+emptyIdeState = IdeState emptyFileState emptyVolatileState emptyModifierState
 
 emptyFileState :: IdeFileState
 emptyFileState = IdeFileState M.empty M.empty
@@ -189,6 +190,8 @@ emptyFileState = IdeFileState M.empty M.empty
 emptyVolatileState :: IdeVolatileState
 emptyVolatileState = IdeVolatileState (AstData M.empty) M.empty Nothing
 
+emptyModifierState :: IdeModifierState
+emptyModifierState = IdeModifierState mempty
 
 -- | @IdeFileState@ holds data that corresponds 1-to-1 to an entity on the
 -- filesystem. Externs correspond to the ExternsFiles the compiler emits into
@@ -213,6 +216,10 @@ data IdeVolatileState = IdeVolatileState
   , vsCachedRebuild :: Maybe (P.ModuleName, P.ExternsFile)
   } deriving (Show)
 
+data IdeModifierState = IdeModifierState
+  { mdFocusedModules :: Set P.ModuleName
+  } deriving (Show)
+
 newtype Match a = Match (P.ModuleName, a)
            deriving (Show, Eq, Functor)
 

From d2758699f1f78a1c51a43640242bd034ccce87db Mon Sep 17 00:00:00 2001
From: Justin Garcia <purefunctor@gmail.com>
Date: Wed, 31 Jul 2024 04:27:53 +0800
Subject: [PATCH 3/4] Rename to IdeDurableState

---
 src/Language/PureScript/Ide/State.hs | 30 ++++++++++++++--------------
 src/Language/PureScript/Ide/Types.hs | 18 +++++++++++------
 2 files changed, 27 insertions(+), 21 deletions(-)

diff --git a/src/Language/PureScript/Ide/State.hs b/src/Language/PureScript/Ide/State.hs
index 02481b305a..f11f00ad81 100644
--- a/src/Language/PureScript/Ide/State.hs
+++ b/src/Language/PureScript/Ide/State.hs
@@ -65,7 +65,8 @@ import System.Directory (getModificationTime)
 resetIdeState :: Ide m => m ()
 resetIdeState = do
   ideVar <- ideStateVar <$> ask
-  liftIO (atomically (writeTVar ideVar emptyIdeState))
+  durableState <- getDurableState
+  liftIO (atomically (writeTVar ideVar (emptyIdeState { ideDurableState = durableState })))
 
 getOutputDirectory :: Ide m => m FilePath
 getOutputDirectory = do
@@ -145,21 +146,21 @@ setVolatileStateSTM ref vs = do
     x {ideVolatileState = vs}
   pure ()
 
--- | Retrieves the ModifierState from the State.
-getModifierState :: Ide m => m IdeModifierState
-getModifierState = do
+-- | Retrieves the DurableState from the State.
+getDurableState :: Ide m => m IdeDurableState
+getDurableState = do
   st <- ideStateVar <$> ask
-  liftIO (atomically (getModifierStateSTM st))
+  liftIO (atomically (getDurableStateSTM st))
 
--- | STM version of getModifierState
-getModifierStateSTM :: TVar IdeState -> STM IdeModifierState
-getModifierStateSTM ref = ideModifierState <$> readTVar ref
+-- | STM version of getDurableState
+getDurableStateSTM :: TVar IdeState -> STM IdeDurableState
+getDurableStateSTM ref = ideDurableState <$> readTVar ref
 
--- | Sets the ModifierState inside Ide's state
-setModifierStateSTM :: TVar IdeState -> IdeModifierState -> STM ()
-setModifierStateSTM ref md = do
+-- | Sets the DurableState inside Ide's state
+setDurableStateSTM :: TVar IdeState -> IdeDurableState -> STM ()
+setDurableStateSTM ref md = do
   modifyTVar ref $ \x ->
-    x {ideModifierState = md}
+    x {ideDurableState = md}
   pure ()
 
 -- | Checks if the given ModuleName matches the last rebuild cache and if it
@@ -471,7 +472,7 @@ resolveDataConstructorsForModule decls =
 
 getFocusedModules :: Ide m => m (Set P.ModuleName)
 getFocusedModules = do
-  IdeModifierState{mdFocusedModules = focusedModules} <- getModifierState
+  IdeDurableState{drFocusedModules = focusedModules} <- getDurableState
   pure focusedModules
 
 setFocusedModules :: Ide m => [P.ModuleName] -> m ()
@@ -481,5 +482,4 @@ setFocusedModules modulesToFocus = do
 
 setFocusedModulesSTM :: TVar IdeState -> [P.ModuleName] -> STM ()
 setFocusedModulesSTM ref modulesToFocus = do
-  IdeModifierState{} <- getModifierStateSTM ref
-  setModifierStateSTM ref (IdeModifierState (Set.fromList modulesToFocus))
+  setDurableStateSTM ref (IdeDurableState (Set.fromList modulesToFocus))
diff --git a/src/Language/PureScript/Ide/Types.hs b/src/Language/PureScript/Ide/Types.hs
index 8f8e84e18a..e51acc69a0 100644
--- a/src/Language/PureScript/Ide/Types.hs
+++ b/src/Language/PureScript/Ide/Types.hs
@@ -15,6 +15,7 @@ import Data.Aeson qualified as Aeson
 import Data.IORef (IORef)
 import Data.Time.Clock (UTCTime)
 import Data.Map.Lazy qualified as M
+import Data.Set qualified as S
 import Language.PureScript qualified as P
 import Language.PureScript.Errors.JSON qualified as P
 import Language.PureScript.Ide.Filter.Declaration (DeclarationType(..))
@@ -178,11 +179,11 @@ type Ide m = (MonadIO m, MonadReader IdeEnvironment m)
 data IdeState = IdeState
   { ideFileState :: IdeFileState
   , ideVolatileState :: IdeVolatileState
-  , ideModifierState :: IdeModifierState
+  , ideDurableState :: IdeDurableState
   } deriving (Show)
 
 emptyIdeState :: IdeState
-emptyIdeState = IdeState emptyFileState emptyVolatileState emptyModifierState
+emptyIdeState = IdeState emptyFileState emptyVolatileState emptyDurableState
 
 emptyFileState :: IdeFileState
 emptyFileState = IdeFileState M.empty M.empty
@@ -190,8 +191,8 @@ emptyFileState = IdeFileState M.empty M.empty
 emptyVolatileState :: IdeVolatileState
 emptyVolatileState = IdeVolatileState (AstData M.empty) M.empty Nothing
 
-emptyModifierState :: IdeModifierState
-emptyModifierState = IdeModifierState mempty
+emptyDurableState :: IdeDurableState
+emptyDurableState = IdeDurableState S.empty
 
 -- | @IdeFileState@ holds data that corresponds 1-to-1 to an entity on the
 -- filesystem. Externs correspond to the ExternsFiles the compiler emits into
@@ -216,8 +217,13 @@ data IdeVolatileState = IdeVolatileState
   , vsCachedRebuild :: Maybe (P.ModuleName, P.ExternsFile)
   } deriving (Show)
 
-data IdeModifierState = IdeModifierState
-  { mdFocusedModules :: Set P.ModuleName
+-- | @IdeDurableState@ holds data that persists across resets of the @IdeState@.
+-- This is particularly useful for configuration variables that can be modified
+-- during runtime. For instance, the module names for the "focus" feature are 
+-- stored in the drFocusedModules field, which the client populates using the
+-- @Focus@ command to specify only which modules to load.
+data IdeDurableState = IdeDurableState
+  { drFocusedModules :: Set P.ModuleName
   } deriving (Show)
 
 newtype Match a = Match (P.ModuleName, a)

From 9e5f7b902e7dc50e677a5935b0a5425cb4d9461d Mon Sep 17 00:00:00 2001
From: Justin Garcia <purefunctor@gmail.com>
Date: Wed, 31 Jul 2024 04:28:08 +0800
Subject: [PATCH 4/4] Refactor command handling in startServer

---
 app/Command/Ide.hs | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/app/Command/Ide.hs b/app/Command/Ide.hs
index f5a501af75..38fc9c7e36 100644
--- a/app/Command/Ide.hs
+++ b/app/Command/Ide.hs
@@ -28,7 +28,7 @@ import Data.ByteString.Char8 qualified as BS8
 import Data.ByteString.Lazy.Char8 qualified as BSL8
 import GHC.IO.Exception (IOErrorType(..), IOException(..))
 import Language.PureScript.Ide (handleCommand)
-import Language.PureScript.Ide.Command (Command(..), commandName)
+import Language.PureScript.Ide.Command (commandName, Command(..))
 import Language.PureScript.Ide.Util (decodeT, displayTimeSpec, encodeT, logPerf, runLogger)
 import Language.PureScript.Ide.Error (IdeError(..))
 import Language.PureScript.Ide.State (updateCacheTimestamp)
@@ -199,14 +199,22 @@ startServer port env = Network.withSocketsDo $ do
               logPerf message $ do
                 result <- runExceptT $ do
                   updateCacheTimestamp >>= \case
-                    Nothing -> pure ()
+                    Nothing -> 
+                      handleCommand cmd'
                     Just (before, after) -> do
                       -- If the cache db file was changed outside of the IDE
                       -- we trigger a reset before processing the command
                       $(logInfo) ("cachedb was changed from: " <> show before <> ", to: " <> show after)
-                      unless (isLoadAll cmd') $
-                        void (handleCommand Reset *> handleCommand (LoadSync []))
-                  handleCommand cmd'
+                      let doReload = handleCommand Reset *> handleCommand (LoadSync [])
+                      case cmd' of
+                        -- handleCommand on Load [] already resets the state.
+                        Load [] -> handleCommand cmd'
+                        -- Focus needs to fire before doReload, because we
+                        -- want to set the focused modules first before
+                        -- loading everything with LoadSync [].
+                        Focus _ -> handleCommand cmd' <* doReload
+                        -- Otherwise, just doReload and then handle.
+                        _ -> doReload *> handleCommand cmd'
                 liftIO $ catchGoneHandle $ BSL8.hPutStrLn h $ case result of
                   Right r  -> Aeson.encode r
                   Left err -> Aeson.encode err
@@ -219,11 +227,6 @@ startServer port env = Network.withSocketsDo $ do
                 hFlush stdout
           liftIO $ catchGoneHandle (hClose h)
 
-isLoadAll :: Command -> Bool
-isLoadAll = \case
-  Load [] -> True
-  _ -> False
-
 catchGoneHandle :: IO () -> IO ()
 catchGoneHandle =
   handle (\e -> case e of