Merge pull request #11134 from webpack/feature/check-asset-casing

add error when trying to write assets that only differ in casing

lib/Compiler.js

@@ -14,7 +14,6 @@ const {
 	AsyncSeriesHook
 } = require("tapable");
 const { SizeOnlySource } = require("webpack-sources");
-
 const Cache = require("./Cache");
 const Compilation = require("./Compilation");
 const ConcurrentCompilationError = require("./ConcurrentCompilationError");
@@ -24,6 +23,7 @@ const RequestShortener = require("./RequestShortener");
 const ResolverFactory = require("./ResolverFactory");
 const Stats = require("./Stats");
 const Watching = require("./Watching");
+const WebpackError = require("./WebpackError");
 const { Logger } = require("./logging/Logger");
 const { join, dirname, mkdirp } = require("./util/fs");
 const { makePathsRelative } = require("./util/identifier");
@@ -480,6 +480,7 @@ class Compiler {
 
 			const assets = compilation.getAssets();
 			compilation.assets = { ...compilation.assets };
+			const caseInsensitiveMap = new Map();
 			asyncLib.forEachLimit(
 				assets,
 				15,
@@ -498,6 +499,19 @@ class Compiler {
 							targetFile
 						);
 
+						const caseInsensitiveTargetPath = targetPath.toLowerCase();
+						if (caseInsensitiveMap.has(caseInsensitiveTargetPath)) {
+							const other = caseInsensitiveMap.get(caseInsensitiveTargetPath);
+							const err = new WebpackError(`Prevent writing to file that only differs in casing from already written file.
+This will lead to a race-condition and corrupted files on case-insensitive file systems.
+${targetPath}
+${other}`);
+							err.file = file;
+							return callback(err);
+						} else {
+							caseInsensitiveMap.set(caseInsensitiveTargetPath, targetPath);
+						}
+
 						// check if the target file has already been written by this Compiler
 						const targetFileGeneration = this._assetEmittingWrittenFiles.get(
 							targetPath

test/configCases/errors/case-emit/errors.js

@@ -0,0 +1 @@
+module.exports = [[/only differs in casing/, /a\.js/, /A\.js/]];

test/configCases/errors/case-emit/webpack.config.js

@@ -0,0 +1,10 @@
+/** @type {import("../../../../").Configuration} */
+module.exports = {
+	entry: {
+		a: "./index.js?1",
+		A: "./index.js?2"
+	},
+	output: {
+		filename: "[name].js"
+	}
+};