fix: prevent TypeError when child compilations have missing assets (#741)

* fix: prevent TypeError when child compilations have missing assets

* fix: populate changeset, preserve child compilations via WeakMap, and improve coverage

* fix: preserve entrypoint metadata for appended child compilations

Author: ronakmaheshwari

.changeset/fix-child-compilations-type-error.md

@@ -0,0 +1,5 @@
+---
+"webpack-bundle-analyzer": patch
+---
+
+Fix `TypeError: Cannot read property 'forEach' of undefined` when child compilations or entrypoints have undefined or missing assets.

src/analyzer.js

@@ -79,20 +79,22 @@ function flatten(arr) {
 }
 
 /**
- * @param {StatsCompilation} bundleStats bundle stats
+ * @param {StatsCompilation[]} children child stats list
  * @param {string} assetName asset name
- * @returns {boolean} child asset bundlers
+ * @returns {StatsCompilation | undefined} child asset compilation
  */
-function getChildAssetBundles(bundleStats, assetName) {
-  return flatten(
-    (bundleStats.children || /** @type {StatsCompilation} */ ([])).find(
-      /**
-       * @param {StatsCompilation} child child stats
-       * @returns {string[][]} assets by chunk name
-       */
-      (child) => Object.values(child.assetsByChunkName || []),
-    ),
-  ).includes(assetName);
+function getChildAssetBundles(children, assetName) {
+  return children.find((child) => {
+    if (!child) return false;
+    if (
+      Array.isArray(child.assets) &&
+      child.assets.some((asset) => asset && asset.name === assetName)
+    ) {
+      return true;
+    }
+    const chunkAssets = flatten(Object.values(child.assetsByChunkName || {}));
+    return chunkAssets.includes(assetName);
+  });
 }
 
 /**
@@ -195,7 +197,7 @@ function getAssetModulesByChunk(statsAsset, modulesByChunk) {
 /** @typedef {Record<string, Record<string, boolean>>} ChunkToInitialByEntrypoint */
 
 /**
- * @param {StatsCompilation} bundleStats bundle stats
+ * @param {StatsCompilation | undefined} bundleStats bundle stats
  * @returns {ChunkToInitialByEntrypoint} chunk to initial by entrypoint
  */
 function getChunkToInitialByEntrypoint(bundleStats) {
@@ -206,8 +208,10 @@ function getChunkToInitialByEntrypoint(bundleStats) {
   const chunkToEntrypointInititalMap = {};
   for (const entrypoint of Object.values(bundleStats.entrypoints || {})) {
     for (const asset of entrypoint.assets || []) {
-      chunkToEntrypointInititalMap[asset.name] ??= {};
-      chunkToEntrypointInititalMap[asset.name][
+      const assetName = typeof asset === "string" ? asset : asset?.name;
+      if (!assetName) continue;
+      chunkToEntrypointInititalMap[assetName] ??= {};
+      chunkToEntrypointInititalMap[assetName][
         /** @type {string} */
         (entrypoint.name)
       ] = true;
@@ -255,7 +259,7 @@ function isEntryModule(statsModule) {
  */
 
 /**
- * @param {StatsCompilation} bundleStats bundle stats
+ * @param {StatsCompilation | StatsCompilation[]} bundleStats bundle stats
  * @param {string | null} bundleDir bundle dir
  * @param {ViewerDataOptions=} opts options
  * @returns {ChartData} chart data
@@ -267,34 +271,54 @@ function getViewerData(bundleStats, bundleDir, opts) {
     excludeAssets = null,
   } = opts || {};
 
+  if (!bundleStats) return [];
+
+  if (Array.isArray(bundleStats)) {
+    bundleStats = {
+      children: bundleStats,
+    };
+  }
+
   const isAssetIncluded = createAssetsFilter(excludeAssets);
 
+  // Preserve all children from the root bundleStats (e.g. for MultiCompiler or child compilations)
+  const allChildren = Array.isArray(bundleStats.children)
+    ? [...bundleStats.children]
+    : [];
+  /** @type {WeakMap<StatsAsset, StatsCompilation>} */
+  const childAssetBundles = new WeakMap();
+
   // Sometimes all the information is located in `children` array (e.g. problem in #10)
   if (
     (bundleStats.assets === null ||
       bundleStats.assets === undefined ||
       bundleStats.assets.length === 0) &&
-    bundleStats.children &&
-    bundleStats.children.length > 0
+    allChildren.length > 0
   ) {
-    const { children } = bundleStats;
-    [bundleStats] = bundleStats.children;
+    bundleStats = { ...allChildren[0] };
+    bundleStats.assets = Array.isArray(bundleStats.assets)
+      ? [...bundleStats.assets]
+      : [];
+
     // Sometimes if there are additional child chunks produced add them as child assets,
     // leave the 1st one as that is considered the 'root' asset.
-    for (let i = 1; i < children.length; i++) {
-      for (const asset of children[i].assets || []) {
+    for (let i = 1; i < allChildren.length; i++) {
+      const child = allChildren[i];
+      for (const asset of child?.assets || []) {
+        childAssetBundles.set(asset, child);
         asset.isChild = true;
-        /** @type {StatsAsset[]} */
-        (bundleStats.assets).push(asset);
+        bundleStats.assets.push(asset);
       }
     }
-  } else if (bundleStats.children && bundleStats.children.length > 0) {
+  } else if (allChildren.length > 0) {
+    bundleStats.assets = [.../** @type {StatsAsset[]} */ (bundleStats.assets)];
+
     // Sometimes if there are additional child chunks produced add them as child assets
-    for (const child of bundleStats.children) {
-      for (const asset of child.assets || []) {
+    for (const child of allChildren) {
+      for (const asset of child?.assets || []) {
+        childAssetBundles.set(asset, child);
         asset.isChild = true;
-        /** @type {StatsAsset[]} */
-        (bundleStats.assets).push(asset);
+        bundleStats.assets.push(asset);
       }
     }
   }
@@ -395,27 +419,35 @@ function getViewerData(bundleStats, bundleDir, opts) {
     }
   }
 
-  /** @typedef {{ size: number, parsedSize?: number, gzipSize?: number, brotliSize?: number, zstdSize?: number, modules: StatsModule[], tree: Folder }} Asset */
+  const rootChunkToInitialByEntrypoint =
+    getChunkToInitialByEntrypoint(bundleStats);
+
+  /** @typedef {{ size: number, parsedSize?: number, gzipSize?: number, brotliSize?: number, zstdSize?: number, modules: StatsModule[], tree: Folder, isInitialByEntrypoint: Record<string, boolean> }} Asset */
 
   const assets = bundleStats.assets.reduce((result, statAsset) => {
     /** @type {StatsModule[]} */
     let assetModules;
+    /** @type {Record<string, boolean>} */
+    let isInitialByEntrypoint;
 
     if (statAsset.isChild) {
       // Preserve child-compilation matching because child assets use a different module list.
-      const assetBundles = getChildAssetBundles(bundleStats, statAsset.name);
+      const assetBundles =
+        childAssetBundles.get(statAsset) ||
+        getChildAssetBundles(allChildren, statAsset.name);
       /** @type {StatsModule[]} */
-      const modules = assetBundles
-        ? // @ts-expect-error TODO looks like we have a bug with child compilation parsing, need to add test cases
-          getBundleModules(assetBundles)
-        : [];
+      const modules = assetBundles ? getBundleModules(assetBundles) : [];
       assetModules = modules.filter((statModule) =>
         assetHasModule(statAsset, statModule),
       );
+      isInitialByEntrypoint =
+        getChunkToInitialByEntrypoint(assetBundles)[statAsset.name] ?? {};
     } else {
       assetModules = /** @type {StatsModule[]} */ (
-        rootAssetModules.get(statAsset)
+        rootAssetModules.get(statAsset) || []
       );
+      isInitialByEntrypoint =
+        rootChunkToInitialByEntrypoint[statAsset.name] ?? {};
     }
 
     // A module that is a part of more than one asset is one stats object. Every asset that
@@ -426,6 +458,7 @@ function getViewerData(bundleStats, bundleDir, opts) {
 
     const asset = (result[statAsset.name] = /** @type {Asset} */ ({
       size: statAsset.size,
+      isInitialByEntrypoint,
     }));
     const assetSources =
       bundlesSources && Object.hasOwn(bundlesSources, statAsset.name)
@@ -503,8 +536,6 @@ function getViewerData(bundleStats, bundleDir, opts) {
     return result;
   }, /** @type {Record<string, Asset>} */ ({}));
 
-  const chunkToInitialByEntrypoint = getChunkToInitialByEntrypoint(bundleStats);
-
   return Object.entries(assets).map(([filename, asset]) => ({
     label: filename,
     isAsset: true,
@@ -518,7 +549,7 @@ function getViewerData(bundleStats, bundleDir, opts) {
     brotliSize: asset.brotliSize,
     zstdSize: asset.zstdSize,
     groups: Object.values(asset.tree.children).map((i) => i.toChartData()),
-    isInitialByEntrypoint: chunkToInitialByEntrypoint[filename] ?? {},
+    isInitialByEntrypoint: asset.isInitialByEntrypoint,
   }));
 }