fix #4121: map js regexp flags to go regexp flags

Author: evanw

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+* Support flags in regular expressions for the API ([#4121](https://github.com/evanw/esbuild/issues/4121))
+
+    The JavaScript plugin API for esbuild takes JavaScript regular expression objects for the `filter` option. Internally these are translated into Go regular expressions. However, this translation previously ignored the `flags` property of the regular expression. With this release, esbuild will now translate JavaScript regular expression flags into Go regular expression flags. Specifically the JavaScript regular expression `/\.[jt]sx?$/i` is turned into the Go regular expression `` `(?i)\.[jt]sx?$` `` internally inside of esbuild's API. This should make it possible to use JavaScript regular expressions with the `i` flag. Note that JavaScript and Go don't support all of the same regular expression features, so this mapping is only approximate.
+
 * Fix node-specific annotations for string literal export names ([#4100](https://github.com/evanw/esbuild/issues/4100))
 
     When node instantiates a CommonJS module, it scans the AST to look for names to expose via ESM named exports. This is a heuristic that looks for certain patterns such as `exports.NAME = ...` or `module.exports = { ... }`. This behavior is used by esbuild to "annotate" CommonJS code that was converted from ESM with the original ESM export names. For example, when converting the file `export let foo, bar` from ESM to CommonJS, esbuild appends this to the end of the file:

lib/shared/common.ts

@@ -190,8 +190,8 @@ function pushCommonFlags(flags: string[], options: CommonOptions, keys: OptionKe
   if (ignoreAnnotations) flags.push(`--ignore-annotations`)
   if (drop) for (let what of drop) flags.push(`--drop:${validateStringValue(what, 'drop')}`)
   if (dropLabels) flags.push(`--drop-labels=${Array.from(dropLabels).map(what => validateStringValue(what, 'dropLabels')).join(',')}`)
-  if (mangleProps) flags.push(`--mangle-props=${mangleProps.source}`)
-  if (reserveProps) flags.push(`--reserve-props=${reserveProps.source}`)
+  if (mangleProps) flags.push(`--mangle-props=${jsRegExpToGoRegExp(mangleProps)}`)
+  if (reserveProps) flags.push(`--reserve-props=${jsRegExpToGoRegExp(reserveProps)}`)
   if (mangleQuoted !== void 0) flags.push(`--mangle-quoted=${mangleQuoted}`)
 
   if (jsx) flags.push(`--jsx=${jsx}`)
@@ -1316,7 +1316,7 @@ let handlePlugins = async (
           if (filter == null) throw new Error(`onResolve() call is missing a filter`)
           let id = nextCallbackID++
           onResolveCallbacks[id] = { name: name!, callback, note: registeredNote }
-          plugin.onResolve.push({ id, filter: filter.source, namespace: namespace || '' })
+          plugin.onResolve.push({ id, filter: jsRegExpToGoRegExp(filter), namespace: namespace || '' })
         },
 
         onLoad(options, callback) {
@@ -1329,7 +1329,7 @@ let handlePlugins = async (
           if (filter == null) throw new Error(`onLoad() call is missing a filter`)
           let id = nextCallbackID++
           onLoadCallbacks[id] = { name: name!, callback, note: registeredNote }
-          plugin.onLoad.push({ id, filter: filter.source, namespace: namespace || '' })
+          plugin.onLoad.push({ id, filter: jsRegExpToGoRegExp(filter), namespace: namespace || '' })
         },
 
         onDispose(callback) {
@@ -1859,3 +1859,9 @@ function convertOutputFiles({ path, contents, hash }: protocol.BuildOutputFile):
     },
   }
 }
+
+function jsRegExpToGoRegExp(regexp: RegExp): string {
+  let result = regexp.source
+  if (regexp.flags) result = `(?${regexp.flags})${result}`
+  return result
+}

scripts/plugin-tests.js

@@ -145,6 +145,48 @@ let pluginTests = {
     }
   },
 
+  async caseInsensitiveRegExp({ esbuild, testDir }) {
+    const inputJs = path.join(testDir, 'in.js')
+    await writeFileAsync(inputJs, `export default 123`)
+
+    const inputCpp = path.join(testDir, 'in.CpP')
+    await writeFileAsync(inputCpp, `export default 123`)
+
+    // onResolve
+    const onResolveResult = await esbuild.build({
+      entryPoints: ['example.CpP'],
+      write: false,
+      plugins: [{
+        name: 'name',
+        setup(build) {
+          build.onResolve({ filter: /\.c(pp|xx)?$/i }, args => {
+            assert.strictEqual(args.path, 'example.CpP')
+            return { path: inputJs }
+          })
+        },
+      }],
+    })
+    assert.strictEqual(onResolveResult.outputFiles.length, 1)
+    assert.strictEqual(onResolveResult.outputFiles[0].text, `export default 123;\n`)
+
+    // onLoad
+    const onLoadResult = await esbuild.build({
+      entryPoints: [inputCpp],
+      write: false,
+      plugins: [{
+        name: 'name',
+        setup(build) {
+          build.onLoad({ filter: /\.c(pp|xx)?$/i }, args => {
+            assert(args.path.endsWith('in.CpP'))
+            return { contents: 'export default true' }
+          })
+        },
+      }],
+    })
+    assert.strictEqual(onLoadResult.outputFiles.length, 1)
+    assert.strictEqual(onLoadResult.outputFiles[0].text, `export default true;\n`)
+  },
+
   async pluginMissingName({ esbuild }) {
     try {
       await esbuild.build({