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Implement a Source cache to avoid over-eager emitting #12

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Implement a Source cache to avoid over-eager emitting #12

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37 changes: 32 additions & 5 deletions wrapper-webpack-plugin.js
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Original file line number Diff line number Diff line change
Expand Up @@ -24,12 +24,19 @@ class WrapperPlugin {
this.footer = args.hasOwnProperty('footer') ? args.footer : '';
this.afterOptimizations = args.hasOwnProperty('afterOptimizations') ? !!args.afterOptimizations : false;
this.test = args.hasOwnProperty('test') ? args.test : '';

// Webpack has an internal cache based on Source identity that it uses to determine
// whether or not to re-emit assets. We use this cache to ensure that we only re-emit
// if the contents of the asset have changed, by re-using the previous Source object
// otherwise to maintain this integrity.
this._cache = new WeakMap();
}

apply(compiler) {
const header = this.header;
const footer = this.footer;
const tester = {test: this.test};
const cache = this._cache;

compiler.hooks.compilation.tap('WrapperPlugin', (compilation) => {
if (this.afterOptimizations) {
Expand All @@ -48,11 +55,31 @@ class WrapperPlugin {
const headerContent = (typeof header === 'function') ? header(fileName, chunkHash) : header;
const footerContent = (typeof footer === 'function') ? footer(fileName, chunkHash) : footer;

compilation.assets[fileName] = new ConcatSource(
String(headerContent),
compilation.assets[fileName],
String(footerContent),
);
const headerContentString = String(headerContent);
const footerContentString = String(footerContent);

const cacheKey = compilation.assets[fileName];
let content = null;
if (cache.has(cacheKey)) {
content = cache.get(cacheKey);
if (content.header !== headerContentString || content.footer !== footerContentString) {
content = null;
}
}

if (!content) {
content = {
header: headerContentString,
footer: footerContentString,
source: new ConcatSource(
headerContentString,
compilation.assets[fileName],
footerContentString)
}
cache.set(compilation.assets[fileName], content)
}

compilation.assets[fileName] = content.source;
}

function wrapChunks(compilation, chunks) {
Expand Down