Merge pull request #11628 from webpack/bugfix/real-content-hash

emit error instead of crashing when unexpected problem occurs

lib/optimize/RealContentHashPlugin.js

@@ -7,6 +7,7 @@
 
 const { RawSource, CachedSource, CompatSource } = require("webpack-sources");
 const Compilation = require("../Compilation");
+const WebpackError = require("../WebpackError");
 const { compareSelect, compareStrings } = require("../util/comparators");
 const createHash = require("../util/createHash");
 
@@ -141,6 +142,26 @@ class RealContentHashPlugin {
 					);
 					const getDependencies = hash => {
 						const assets = hashToAssets.get(hash);
+						if (!assets) {
+							const referencingAssets = assetsWithInfo.filter(asset =>
+								asset.referencedHashes.has(hash)
+							);
+							const err = new WebpackError(`RealContentHashPlugin
+Some kind of unexpected caching problem occurred.
+An asset was cached with a reference to another asset (${hash}) that's not in the compilation anymore.
+Either the asset was incorrectly cached, or the referenced asset should also be restored from cache.
+Referenced by:
+${referencingAssets
+	.map(a => {
+		const match = new RegExp(`.{0,20}${quoteMeta(hash)}.{0,20}`).exec(
+			a.content
+		);
+		return ` - ${a.name}: ...${match ? match[0] : "???"}...`;
+	})
+	.join("\n")}`);
+							compilation.errors.push(err);
+							return undefined;
+						}
 						const hashes = new Set();
 						for (const { referencedHashes } of assets) {
 							for (const hash of referencedHashes) {
@@ -157,6 +178,7 @@ class RealContentHashPlugin {
 					for (const hash of hashToAssets.keys()) {
 						const add = (hash, stack) => {
 							const deps = getDependencies(hash);
+							if (!deps) return;
 							stack.add(hash);
 							for (const dep of deps) {
 								if (hashesInOrder.has(dep)) continue;