Add Experimental Feature @nullIfNotFound() for Existing Resources

[tsmallig33]

Description

Adds nullable existing resource support with @nullIfNotFound decorator. Note, @nullIfNotFound() will not work until backend changes have been deployed

Example Usage

@nullIfNotFound()
resource storageAccount 'Microsoft.Storage/storageAccounts@2021-04-01' existing = {
  name: 'testStorage'
}

output safeLocation string? = storageAccount.?location
output safeSkuName string? = storageAccount.?sku.name
output safeAccessTier string? = storageAccount.?properties.accessTier

output locationWithDefault string = storageAccount.?location ?? 'westus'
output skuNameWithDefault string = storageAccount.?sku.name ?? 'Standard_LRS'
output accessTierWithDefault string = storageAccount.?properties.accessTier ?? 'Hot'

Checklist

• I have read and adhere to the contribution guide.

Microsoft Reviewers: Open in CodeFlow

[github-actions]

Test this change out locally with the following install scripts (Action run 20277551735)

VSCode

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-vsix.sh) --run-id 20277551735

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-vsix.ps1) } -RunId 20277551735"

Azure CLI

• Mac/Linux

  bash <(curl -Ls https://aka.ms/bicep/nightly-cli.sh) --run-id 20277551735

• Windows

  iex "& { $(irm https://aka.ms/bicep/nightly-cli.ps1) } -RunId 20277551735"

[github-actions]

Dotnet Test Results

   102 files   -     51     102 suites   - 51   39m 47s ⏱️ - 19m 52s
12 592 tests +     2  12 592 ✅ +     2  0 💤 ±0  0 ❌ ±0 
28 929 runs   - 14 413  28 929 ✅  - 14 413  0 💤 ±0  0 ❌ ±0 

Results for commit 0c7e587. ± Comparison against base commit 56292d6.

This pull request removes 1956 and adds 676 tests. Note that renamed tests count towards both.

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Bicep.Cli.UnitTests.Services.ReplEnvironmentTests ‑ ShouldSubmitBuffer_terminates_at_expected_point ("var foo = {
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Bicep.Cli.UnitTests.Services.ReplEnvironmentTests ‑ ShouldSubmitBuffer_terminates_at_expected_point ("var multilineString = '''
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'''")
Bicep.Cli.UnitTests.Services.ReplEnvironmentTests ‑ ShouldSubmitBuffer_terminates_at_expected_point ("var outRoleAssignments object[] = union(map(
  filter(varMockedEntraGroupIds, item => !contains(item.uniqueName, 'DevOps')),
  group => {
    principalId: group.groupId
    definition: group.roleToAssign
    relativeScope: ''
    principalType: 'Group'
  }
),[
  {
    principalId: '22222222-2222-2222-2222-222222222222'
    definition: 'Reader'
    relativeScope: ''
    principalType: 'ServicePrincipal'
  }
])")
Bicep.Cli.UnitTests.Services.ReplEnvironmentTests ‑ ShouldSubmitBuffer_terminates_at_expected_point ("var test = {
  abc: 'def' // boo
}")
Bicep.Cli.UnitTests.Services.ReplEnvironmentTests ‑ ShouldSubmitBuffer_terminates_at_expected_point ("var varMockedEntraGroupIds = [
  {
    uniqueName: 'Reader-Group'
    roleToAssign: 'Reader'
    groupId: '11111111-1111-1111-1111-111111111111'
  }
  {
    uniqueName: 'Contributor-Group'
    roleToAssign: 'Contributor'
    groupId: '22222222-2222-2222-2222-222222222222'
  }
  {
    uniqueName: 'DevOps-Group'
    groupId: '33333333-3333-3333-3333-333333333333'
  }
]")
Bicep.Core.IntegrationTests.AzTypesViaRegistryTests ‑ Bicep_compiler_handles_corrupted_extension_package_gracefully (\u001f�\u0008\u0000\u0000\u0000\u0000\u0000\u0000
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;�{C��o�<��`2op'}�\u0000\u000c\u0000\u0000,"Value cannot be null. (Parameter 'source')")
Bicep.Core.IntegrationTests.AzTypesViaRegistryTests ‑ Bicep_compiler_handles_corrupted_extension_package_gracefully (\u001f�\u0008\u0000\u0000\u0000\u0000\u0000\u0000
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�$I\u0012��\u001bN��@\u0000\u000c\u0000\u0000,"The path: index.json was not found in artifact contents")
Bicep.Core.IntegrationTests.AzTypesViaRegistryTests ‑ Bicep_compiler_handles_corrupted_extension_package_gracefully (\u001f�\u0008\u0000\u0000\u0000\u0000\u0000\u0000
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Bicep.Core.IntegrationTests.AzTypesViaRegistryTests ‑ Bicep_compiler_handles_corrupted_extension_package_gracefully (\u001f�\u0008\u0000\u0000\u0000\u0000\u0000\u0000\u0003��=
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Bicep.Core.IntegrationTests.AzTypesViaRegistryTests ‑ Bicep_compiler_handles_corrupted_extension_package_gracefully (\u001f�\u0008\u0000\u0000\u0000\u0000\u0000\u0000\u0003��=
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…

♻️ This comment has been updated with latest results.

[jeskew]

Decorators can be fully qualified, so you can't always make this determination based on syntax alone. There is a helper method that handles instance function calls, but you would need to call it with the model:

bicep/src/Bicep.Core/Semantics/SemanticModelHelper.cs

Lines 48 to 64 in 56292d6

	public static DecoratorSyntax? TryGetDecoratorInNamespace(SemanticModel semanticModel, DecorableSyntax syntax, string @namespace, string decoratorName)
	=> TryGetDecoratorInNamespace(semanticModel.Binder, semanticModel.TypeManager.GetDeclaredType, syntax, @namespace, decoratorName);
	public static DecoratorSyntax? TryGetDecoratorInNamespace(IBinder binder, Func<SyntaxBase, TypeSymbol?> getDeclaredTypeFunc, DecorableSyntax syntax, string @namespace, string decoratorName)
	{
	return syntax.Decorators.FirstOrDefault(decorator =>
	{
	if (SymbolHelper.TryGetSymbolInfo(binder, getDeclaredTypeFunc, decorator.Expression) is not FunctionSymbol functionSymbol ||
	functionSymbol.DeclaringObject is not NamespaceType namespaceType)
	{
	return false;
	}
	return LanguageConstants.IdentifierComparer.Equals(namespaceType.ExtensionName, @namespace) &&
	LanguageConstants.IdentifierComparer.Equals(functionSymbol.Name, decoratorName);
	});
	}

[tsmallig33]

Removed from SyntaxExtensions and added TryGetDecoratorInNamespace to IsResourceEnabled

[jeskew]

Is this the only place .IsNullableExistingResource() is called? If so, you could simplify a bit by doing the decorator check here.