Consider \ and / to be the same in file paths

CHANGELOG.md

@@ -26,6 +26,12 @@
 
     With this release, esbuild's built-in resolver will now automatically consider all import paths starting with `node:` as external. This new behavior is only active when the current platform is set to node such as with `--platform=node`. If you need to customize this behavior, you can write a plugin to intercept these paths and treat them differently.
 
+* Consider `\` and `/` to be the same in file paths ([#1459](https://github.com/evanw/esbuild/issues/1459))
+
+    On Windows, there are many different file paths that can refer to the same underlying file. Windows uses a case-insensitive file system so for example `foo.js` and `Foo.js` are the same file. When bundling, esbuild needs to treat both of these paths as the same to avoid incorrectly bundling the file twice. This is case is already handled by identifying files by their lower-case file path.
+
+    The case that wasn't being handled is the fact that Windows supports two different path separators, `/` and `\`, both of which mean the same thing. For example `foo/bar.js` and `foo\bar.js` are the same file. With this release, this case is also handled by esbuild. Files that are imported in multiple places with inconsistent path separators will now be considered the same file instead of bundling the file multiple times.
+
 ## 0.12.15
 
 * Fix a bug with `var()` in CSS color lowering ([#1421](https://github.com/evanw/esbuild/issues/1421))

internal/bundler/bundler.go

@@ -898,11 +898,12 @@ func loaderFromFileExtension(extensionToLoader map[string]config.Loader, base st
 	return config.LoaderNone
 }
 
-// Identify the path by its lowercase absolute path name. This should
-// hopefully avoid path case issues on Windows, which has case-insensitive
-// file system paths.
-func lowerCaseAbsPathForWindows(absPath string) string {
-	return strings.ToLower(absPath)
+// Identify the path by its lowercase absolute path name with Windows-specific
+// slashes substituted for standard slashes. This should hopefully avoid path
+// issues on Windows where multiple different paths can refer to the same
+// underlying file.
+func canonicalFileSystemPathForWindows(absPath string) string {
+	return strings.ReplaceAll(strings.ToLower(absPath), "\\", "/")
 }
 
 func hashForFileName(hashBytes []byte) string {
@@ -1042,7 +1043,7 @@ func (s *scanner) maybeParseFile(
 	path := resolveResult.PathPair.Primary
 	visitedKey := path
 	if visitedKey.Namespace == "file" {
-		visitedKey.Text = lowerCaseAbsPathForWindows(visitedKey.Text)
+		visitedKey.Text = canonicalFileSystemPathForWindows(visitedKey.Text)
 	}
 
 	// Only parse a given file path once
@@ -1209,14 +1210,14 @@ func (s *scanner) preprocessInjectedFiles() {
 	j := 0
 	for _, absPath := range s.options.InjectAbsPaths {
 		prettyPath := s.res.PrettyPath(logger.Path{Text: absPath, Namespace: "file"})
-		lowerAbsPath := lowerCaseAbsPathForWindows(absPath)
+		absPathKey := canonicalFileSystemPathForWindows(absPath)
 
-		if duplicateInjectedFiles[lowerAbsPath] {
+		if duplicateInjectedFiles[absPathKey] {
 			s.log.AddError(nil, logger.Loc{}, fmt.Sprintf("Duplicate injected file %q", prettyPath))
 			continue
 		}
 
-		duplicateInjectedFiles[lowerAbsPath] = true
+		duplicateInjectedFiles[absPathKey] = true
 		resolveResult := s.res.ResolveAbs(absPath)
 
 		if resolveResult == nil {
@@ -1596,7 +1597,7 @@ func (s *scanner) processScannedFiles() []scannerFile {
 				if resolveResult.PathPair.HasSecondary() {
 					secondaryKey := resolveResult.PathPair.Secondary
 					if secondaryKey.Namespace == "file" {
-						secondaryKey.Text = lowerCaseAbsPathForWindows(secondaryKey.Text)
+						secondaryKey.Text = canonicalFileSystemPathForWindows(secondaryKey.Text)
 					}
 					if secondarySourceIndex, ok := s.visited[secondaryKey]; ok {
 						record.SourceIndex = ast.MakeIndex32(secondarySourceIndex)
@@ -1656,7 +1657,7 @@ func (s *scanner) processScannedFiles() []scannerFile {
 						} else if !css.JSSourceIndex.IsValid() {
 							stubKey := otherFile.inputFile.Source.KeyPath
 							if stubKey.Namespace == "file" {
-								stubKey.Text = lowerCaseAbsPathForWindows(stubKey.Text)
+								stubKey.Text = canonicalFileSystemPathForWindows(stubKey.Text)
 							}
 							sourceIndex := s.allocateSourceIndex(stubKey, cache.SourceIndexJSStubForCSS)
 							source := logger.Source{
@@ -2008,13 +2009,13 @@ func (b *Bundle) Compile(log logger.Log, options config.Options, timer *helpers.
 			for _, sourceIndex := range allReachableFiles {
 				keyPath := b.files[sourceIndex].inputFile.Source.KeyPath
 				if keyPath.Namespace == "file" {
-					lowerAbsPath := lowerCaseAbsPathForWindows(keyPath.Text)
-					sourceAbsPaths[lowerAbsPath] = sourceIndex
+					absPathKey := canonicalFileSystemPathForWindows(keyPath.Text)
+					sourceAbsPaths[absPathKey] = sourceIndex
 				}
 			}
 			for _, outputFile := range outputFiles {
-				lowerAbsPath := lowerCaseAbsPathForWindows(outputFile.AbsPath)
-				if sourceIndex, ok := sourceAbsPaths[lowerAbsPath]; ok {
+				absPathKey := canonicalFileSystemPathForWindows(outputFile.AbsPath)
+				if sourceIndex, ok := sourceAbsPaths[absPathKey]; ok {
 					hint := ""
 					switch logger.API {
 					case logger.CLIAPI:
@@ -2040,12 +2041,12 @@ func (b *Bundle) Compile(log logger.Log, options config.Options, timer *helpers.
 		outputFileMap := make(map[string][]byte)
 		end := 0
 		for _, outputFile := range outputFiles {
-			lowerAbsPath := lowerCaseAbsPathForWindows(outputFile.AbsPath)
-			contents, ok := outputFileMap[lowerAbsPath]
+			absPathKey := canonicalFileSystemPathForWindows(outputFile.AbsPath)
+			contents, ok := outputFileMap[absPathKey]
 
 			// If this isn't a duplicate, keep the output file
 			if !ok {
-				outputFileMap[lowerAbsPath] = outputFile.Contents
+				outputFileMap[absPathKey] = outputFile.Contents
 				outputFiles[end] = outputFile
 				end++
 				continue

scripts/js-api-tests.js

@@ -60,6 +60,30 @@ let buildTests = {
     }
   },
 
+  async windowsBackslashPathTest({ esbuild, testDir }) {
+    let entry = path.join(testDir, 'entry.js');
+    let nested = path.join(testDir, 'nested.js');
+    let outfile = path.join(testDir, 'out.js');
+
+    // On Windows, backslash and forward slash should be treated the same
+    fs.writeFileSync(entry, `
+      import ${JSON.stringify(nested)}
+      import ${JSON.stringify(nested.split(path.sep).join('/'))}
+    `);
+    fs.writeFileSync(nested, `console.log('once')`);
+
+    const result = await esbuild.build({
+      entryPoints: [entry],
+      outfile,
+      bundle: true,
+      write: false,
+      minify: true,
+      format: 'esm',
+    })
+
+    assert.strictEqual(result.outputFiles[0].text, 'console.log("once");\n')
+  },
+
   async workingDirTest({ esbuild, testDir }) {
     let aDir = path.join(testDir, 'a');
     let bDir = path.join(testDir, 'b');