fix #459: add a "public path" option

CHANGELOG.md

@@ -1,5 +1,21 @@
 # Changelog
 
+## Unreleased
+
+* Add `--public-path=` for the `file` loader ([#459](https://github.com/evanw/esbuild/issues/459))
+
+    The `file` loader causes importing a file to cause that file to be copied into the output directory. The name of the file is exported as the default export:
+
+    ```js
+    // Assume ".png" is set to the "file" loader
+    import name from 'images/image.png'
+
+    // This prints something like "image.L3XDQOAT.png"
+    console.log(name)
+    ```
+
+    The new public path setting configures the path prefix. So for example setting it to `https://www.example.com/v1` would change the output text for this example to `https://www.example.com/v1/image.L3XDQOAT.png`.
+
 ## 0.7.16
 
 * Fix backward slashes in source maps on Windows ([#463](https://github.com/evanw/esbuild/issues/463))

README.md

@@ -401,6 +401,7 @@ Advanced options:
   --main-fields=...         Override the main file order in package.json
                             (default "browser,module,main" when platform is
                             browser and "main,module" when platform is node)
+  --public-path=...         Set the base URL for the "file" loader
   --color=...               Force use of color terminal escapes (true | false)
 
 Examples:

cmd/esbuild/main.go

@@ -65,6 +65,7 @@ Advanced options:
   --main-fields=...         Override the main file order in package.json
                             (default "browser,module,main" when platform is
                             browser and "main,module" when platform is node)
+  --public-path=...         Set the base URL for the "file" loader
   --color=...               Force use of color terminal escapes (true | false)
 
 Examples:

internal/bundler/bundler.go

@@ -275,14 +275,15 @@ func parseFile(args parseArgs) {
 		hash := hashForFileName([]byte(source.Contents))
 		ext := path.Ext(args.baseName)
 		baseName := args.baseName[:len(args.baseName)-len(ext)] + "." + hash + ext
+		publicPath := args.options.PublicPath + baseName
 
 		// Determine the destination folder
 		targetFolder := args.options.AbsOutputDir
 
 		// Export the resulting relative path as a string
-		expr := js_ast.Expr{Data: &js_ast.EString{Value: js_lexer.StringToUTF16(baseName)}}
+		expr := js_ast.Expr{Data: &js_ast.EString{Value: js_lexer.StringToUTF16(publicPath)}}
 		ast := js_parser.LazyExportAST(args.log, source, args.options, expr, "")
-		ast.URLForCSS = baseName
+		ast.URLForCSS = publicPath
 		result.file.ignoreIfUnused = true
 		result.file.repr = &reprJS{ast: ast}
 		result.ok = true

internal/config/config.go

@@ -208,6 +208,7 @@ type Options struct {
 	TsConfigOverride  string
 	ExtensionToLoader map[string]Loader
 	OutputFormat      Format
+	PublicPath        string
 
 	// If present, metadata about the bundle is written as JSON here
 	AbsMetadataFile string

lib/common.ts

@@ -125,6 +125,7 @@ function flagsForBuildOptions(options: types.BuildOptions, isTTY: boolean, logLe
   let external = getFlag(options, keys, 'external', mustBeArray);
   let loader = getFlag(options, keys, 'loader', mustBeObject);
   let outExtension = getFlag(options, keys, 'outExtension', mustBeObject);
+  let publicPath = getFlag(options, keys, 'publicPath', mustBeString);
   let entryPoints = getFlag(options, keys, 'entryPoints', mustBeArray);
   let stdin = getFlag(options, keys, 'stdin', mustBeObject);
   let write = getFlag(options, keys, 'write', mustBeBoolean) !== false;
@@ -139,6 +140,7 @@ function flagsForBuildOptions(options: types.BuildOptions, isTTY: boolean, logLe
   if (platform) flags.push(`--platform=${platform}`);
   if (tsconfig) flags.push(`--tsconfig=${tsconfig}`);
   if (resolveExtensions) flags.push(`--resolve-extensions=${resolveExtensions.join(',')}`);
+  if (publicPath) flags.push(`--public-path=${publicPath}`);
   if (mainFields) flags.push(`--main-fields=${mainFields.join(',')}`);
   if (external) for (let name of external) flags.push(`--external:${name}`);
   if (loader) {

lib/types.ts

@@ -41,6 +41,7 @@ export interface BuildOptions extends CommonOptions {
   write?: boolean;
   tsconfig?: string;
   outExtension?: { [ext: string]: string };
+  publicPath?: string;
 
   entryPoints?: string[];
   stdin?: StdinOptions;

pkg/api/api.go

@@ -220,6 +220,7 @@ type BuildOptions struct {
 	ResolveExtensions []string
 	Tsconfig          string
 	OutExtensions     map[string]string
+	PublicPath        string
 
 	EntryPoints []string
 	Stdin       *StdinOptions

pkg/api/api_impl.go

@@ -433,6 +433,10 @@ func buildImpl(buildOpts BuildOptions) BuildResult {
 		ExternalModules:   validateExternals(log, realFS, buildOpts.Externals),
 		TsConfigOverride:  validatePath(log, realFS, buildOpts.Tsconfig),
 		MainFields:        buildOpts.MainFields,
+		PublicPath:        buildOpts.PublicPath,
+	}
+	if options.PublicPath != "" && !strings.HasSuffix(options.PublicPath, "/") && !strings.HasSuffix(options.PublicPath, "\\") {
+		options.PublicPath += "/"
 	}
 	entryPaths := make([]string, len(buildOpts.EntryPoints))
 	for i, entryPoint := range buildOpts.EntryPoints {

pkg/cli/cli_impl.go

@@ -109,6 +109,9 @@ func parseOptionsImpl(osArgs []string, buildOpts *api.BuildOptions, transformOpt
 		case strings.HasPrefix(arg, "--main-fields=") && buildOpts != nil:
 			buildOpts.MainFields = strings.Split(arg[len("--main-fields="):], ",")
 
+		case strings.HasPrefix(arg, "--public-path=") && buildOpts != nil:
+			buildOpts.PublicPath = arg[len("--public-path="):]
+
 		case strings.HasPrefix(arg, "--global-name="):
 			if buildOpts != nil {
 				buildOpts.GlobalName = arg[len("--global-name="):]

scripts/js-api-tests.js

@@ -137,6 +137,66 @@ let buildTests = {
     assert.strictEqual(result.__esModule, true)
   },
 
+  async fileLoader({ esbuild, testDir }) {
+    const input = path.join(testDir, 'in.js')
+    const data = path.join(testDir, 'data.bin')
+    const output = path.join(testDir, 'out.js')
+    await writeFileAsync(input, `export {default as value} from ${JSON.stringify(data)}`)
+    await writeFileAsync(data, `stuff`)
+    const value = await esbuild.build({
+      entryPoints: [input],
+      bundle: true,
+      outfile: output,
+      format: 'cjs',
+      loader: { '.bin': 'file' },
+    })
+    assert.strictEqual(value.outputFiles, void 0)
+    const result = require(output)
+    assert.strictEqual(result.value, 'data.L3XDQOAT.bin')
+    assert.strictEqual(result.__esModule, true)
+  },
+
+  async fileLoaderPublicPath({ esbuild, testDir }) {
+    const input = path.join(testDir, 'in.js')
+    const data = path.join(testDir, 'data.bin')
+    const output = path.join(testDir, 'out.js')
+    await writeFileAsync(input, `export {default as value} from ${JSON.stringify(data)}`)
+    await writeFileAsync(data, `stuff`)
+    const value = await esbuild.build({
+      entryPoints: [input],
+      bundle: true,
+      outfile: output,
+      format: 'cjs',
+      loader: { '.bin': 'file' },
+      publicPath: 'https://www.example.com/assets',
+    })
+    assert.strictEqual(value.outputFiles, void 0)
+    const result = require(output)
+    assert.strictEqual(result.value, 'https://www.example.com/assets/data.L3XDQOAT.bin')
+    assert.strictEqual(result.__esModule, true)
+  },
+
+  async fileLoaderCSS({ esbuild, testDir }) {
+    const input = path.join(testDir, 'in.css')
+    const data = path.join(testDir, 'data.bin')
+    const output = path.join(testDir, 'out.css')
+    await writeFileAsync(input, `body { background: url(${JSON.stringify(data)}) }`)
+    await writeFileAsync(data, `stuff`)
+    const value = await esbuild.build({
+      entryPoints: [input],
+      bundle: true,
+      outfile: output,
+      loader: { '.bin': 'file' },
+      publicPath: 'https://www.example.com/assets',
+    })
+    assert.strictEqual(value.outputFiles, void 0)
+    assert.strictEqual(await readFileAsync(output, 'utf8'), `/* scripts/.js-api-tests/fileLoaderCSS/in.css */
+body {
+  background: url(https://www.example.com/assets/data.L3XDQOAT.bin);
+}
+`)
+  },
+
   async metafile({ esbuild, testDir }) {
     const entry = path.join(testDir, 'entry.js')
     const imported = path.join(testDir, 'imported.js')