Support "extensions" option in config files and presets

packages/babel-cli/src/babel/dir.js

@@ -6,6 +6,7 @@ import { sync as makeDirSync } from "make-dir";
 import slash from "slash";
 import path from "path";
 import fs from "fs";
+import { DEFAULT_EXTENSIONS } from "@babel/core";
 
 import * as util from "./util";
 import { type CmdOptions } from "./options";
@@ -34,7 +35,10 @@ export default async function ({
   ): Promise<$Keys<typeof FILE_TYPE>> {
     let relative = path.relative(base, src);
 
-    if (!util.isCompilableExtension(relative, cliOptions.extensions)) {
+    if (
+      !util.BABEL_SUPPORTS_EXTENSIONS_OPTION &&
+      !util.isCompilableExtension(relative, cliOptions.extensions)
+    ) {
       return FILE_TYPE.NON_COMPILABLE;
     }
 
@@ -48,17 +52,28 @@ export default async function ({
     const dest = getDest(relative, base);
 
     try {
-      const res = await util.compile(
-        src,
+      const config = await util.loadPartialConfig(
         defaults(
           {
             sourceFileName: slash(path.relative(dest + "/..", src)),
+            filename: src,
+            ...(util.BABEL_SUPPORTS_EXTENSIONS_OPTION && {
+              // TODO(Babel 8): At some point @babel/core will default to DEFAULT_EXTENSIONS
+              // instead of ["*"], and we can avoid setting it here.
+              extensions: cliOptions.extensions ?? DEFAULT_EXTENSIONS,
+            }),
           },
           babelOptions,
         ),
       );
 
-      if (!res) return FILE_TYPE.IGNORED;
+      if (!config) return FILE_TYPE.IGNORED;
+
+      const res = await util.compile(src, config.options);
+
+      // If loadPartialConfig didn't return null, it's because the file wasn't ignored.
+      // Thus, if compiling the file returns null, it's because the extension isn't supported.
+      if (!res) return FILE_TYPE.NON_COMPILABLE;
 
       // we've requested explicit sourcemaps to be written to disk
       if (

packages/babel-cli/src/babel/file.js

@@ -226,6 +226,7 @@ export default async function ({
         })
         .on("all", function (type: string, filename: string): void {
           if (
+            !util.BABEL_SUPPORTS_EXTENSIONS_OPTION &&
             !util.isCompilableExtension(filename, cliOptions.extensions) &&
             !filenames.includes(filename)
           ) {

packages/babel-cli/src/babel/util.js

@@ -5,6 +5,11 @@ import * as babel from "@babel/core";
 import path from "path";
 import fs from "fs";
 
+// Technically we could use the "semver" package here, but (for exmaple)
+// parseFloat("4.23.6") returns 4.23 so it's "good enough"
+export const BABEL_SUPPORTS_EXTENSIONS_OPTION =
+  parseFloat(babel.version) >= 7.11;
+
 export function chmod(src: string, dest: string): void {
   fs.chmodSync(dest, fs.statSync(src).mode);
 }
@@ -32,6 +37,10 @@ export function readdirForCompilable(
   includeDotfiles: boolean,
   altExts?: Array<string>,
 ): Array<string> {
+  if (BABEL_SUPPORTS_EXTENSIONS_OPTION) {
+    return readdir(dirname, includeDotfiles);
+  }
+
   return readdir(dirname, includeDotfiles, function (filename) {
     return isCompilableExtension(filename, altExts);
   });
@@ -44,6 +53,12 @@ export function isCompilableExtension(
   filename: string,
   altExts?: Array<string>,
 ): boolean {
+  if (!BABEL_SUPPORTS_EXTENSIONS_OPTION) {
+    throw new Error(
+      "Internal @babel/cli error: isCompilableExtension is only supported with old @babel/core versions.",
+    );
+  }
+
   const exts = altExts || babel.DEFAULT_EXTENSIONS;
   const ext = path.extname(filename);
   return exts.includes(ext);
@@ -76,6 +91,20 @@ export function transform(
   });
 }
 
+export function loadPartialConfig(opts: Object): Promise<Object> {
+  opts = {
+    ...opts,
+    caller: CALLER,
+  };
+
+  return new Promise((resolve, reject) => {
+    babel.loadPartialConfig(opts, (err, result) => {
+      if (err) reject(err);
+      else resolve(result);
+    });
+  });
+}
+
 export function compile(
   filename: string,
   opts: Object | Function,

packages/babel-cli/test/fixtures/babel/--copy-files --no-copy-ignored with only/options.json

@@ -5,7 +5,7 @@
     "lib",
     "--copy-files",
     "--only",
-    "src/foo/*",
+    "src/foo/*,src/README.md",
     "--no-copy-ignored",
     "--verbose"
   ]

packages/babel-cli/test/fixtures/babel/dir uses extensions from config file/in-files/src/.babelrc.json

@@ -0,0 +1,3 @@
+{
+  "extensions": [".tsx"]
+}

packages/babel-cli/test/fixtures/babel/dir uses extensions from config file/in-files/src/bar.ts

@@ -0,0 +1 @@
+x;

packages/babel-cli/test/fixtures/babel/dir uses extensions from config file/in-files/src/baz.js

@@ -0,0 +1 @@
+x;

packages/babel-cli/test/fixtures/babel/dir uses extensions from config file/in-files/src/foo.tsx

@@ -0,0 +1 @@
+x;

packages/babel-cli/test/fixtures/babel/dir uses extensions from config file/options.json

@@ -0,0 +1,3 @@
+{
+  "args": ["src", "--out-dir", "lib"]
+}

packages/babel-cli/test/fixtures/babel/dir uses extensions from config file/out-files/lib/baz.js

@@ -0,0 +1,3 @@
+"use strict";
+
+x;

packages/babel-cli/test/fixtures/babel/dir uses extensions from config file/out-files/lib/foo.js

@@ -0,0 +1,3 @@
+"use strict";
+
+x;

packages/babel-cli/test/fixtures/babel/dir uses extensions from config file/stdout.txt

@@ -0,0 +1 @@
+Successfully compiled 2 files with Babel (123ms).

packages/babel-cli/test/fixtures/babel/env - SHOW_CONFIG_FOR-windows/stdout.txt

@@ -16,6 +16,14 @@ config <CWD>/.babelrc
 programmatic options from @babel/cli
 {
   "sourceFileName": "../src/foo.js",
+  "filename": "src//foo.js",
+  "extensions": [
+    ".js",
+    ".jsx",
+    ".es6",
+    ".es",
+    ".mjs"
+  ],
   "presets": [
     "<ROOTDIR>//packages//babel-preset-react"
   ],
@@ -26,7 +34,6 @@ programmatic options from @babel/cli
   ],
   "caller": {
     "name": "@babel/cli"
-  },
-  "filename": "src//foo.js"
+  }
 }
 Successfully compiled 1 file with Babel (123ms).

packages/babel-core/src/config/full.js

@@ -4,7 +4,7 @@ import gensync, { type Handler } from "gensync";
 import { forwardAsync } from "../gensync-utils/async";
 
 import { mergeOptions } from "./util";
-import * as context from "../index";
+import * as babelContext from "../index";
 import Plugin from "./plugin";
 import { getItemDescriptor } from "./item";
 import {
@@ -70,7 +70,7 @@ export default gensync<[any], ResolvedConfig | null>(function* loadFullConfig(
     return null;
   }
 
-  const optionDefaults = {};
+  const optionDefaults: ValidatedOptions = {};
 
   const { plugins, presets } = options;
 
@@ -161,6 +161,8 @@ export default gensync<[any], ResolvedConfig | null>(function* loadFullConfig(
   const opts: Object = optionDefaults;
   mergeOptions(opts, options);
 
+  if (!isCompilableFile(context.filename, opts.extensions)) return null;
+
   yield* enhanceError(context, function* loadPluginDescriptors() {
     pluginDescriptorsByPass[0].unshift(...initialPluginsDescriptors);
 
@@ -229,7 +231,7 @@ const loadDescriptor = makeWeakCache(function* (
   let item = value;
   if (typeof value === "function") {
     const api = {
-      ...context,
+      ...babelContext,
       ...makeAPI(cache),
     };
     try {
@@ -395,3 +397,8 @@ function chain(a, b) {
     }
   };
 }
+
+function isCompilableFile(filename, extensions) {
+  if (filename == null) return true;
+  return extensions.some(ext => ext === "*" || filename.endsWith(ext));
+}

packages/babel-core/src/config/partial.js

@@ -115,11 +115,19 @@ export default function* loadPrivatePartialConfig(
   const configChain = yield* buildRootChain(args, context);
   if (!configChain) return null;
 
-  const options = {};
+  const options: ValidatedOptions = {};
   configChain.options.forEach(opts => {
     mergeOptions(options, opts);
   });
 
+  // If the programmatic options or config files don't set the "extensions"
+  // option, default to ["*"] for backward compatibility reasons.
+  // Note: this default value is set _before_ loading the presets, so it's
+  // safe to add the "extensions" option to a preset in a minor version.
+  // TODO(Babel 8): The default should be babel.DEFAULT_EXTENSIONS
+  // TODO: Use ??= once flow supports it.
+  options.extensions = options.extensions ?? ["*"];
+
   // Tack the passes onto the object itself so that, if this object is
   // passed back to Babel a second time, it will be in the right structure
   // to not change behavior.

packages/babel-core/src/config/util.js

@@ -2,6 +2,10 @@
 
 import type { ValidatedOptions } from "./validation/options";
 
+function unique<T>(...args: T[]): T[] {
+  return Array.from(new Set(args));
+}
+
 export function mergeOptions(
   target: ValidatedOptions,
   source: ValidatedOptions,
@@ -15,6 +19,11 @@ export function mergeOptions(
       const generatorOpts = source.generatorOpts;
       const targetObj = (target.generatorOpts = target.generatorOpts || {});
       mergeDefaultFields(targetObj, generatorOpts);
+    } else if (k === "extensions" && target.extensions && source.extensions) {
+      target.extensions = unique(
+        ...(target.extensions ?? []),
+        ...source.extensions,
+      );
     } else {
       const val = source[k];
       if (val !== undefined) target[k] = (val: any);

packages/babel-core/src/config/validation/option-assertions.js

@@ -3,7 +3,7 @@
 import type {
   ConfigFileSearch,
   BabelrcSearch,
-  IgnoreList,
+  FileExtension,
   IgnoreItem,
   PluginList,
   PluginItem,
@@ -217,17 +217,20 @@ export function assertArray(
   return value;
 }
 
-export function assertIgnoreList(
-  loc: OptionPath,
-  value: mixed,
-): IgnoreList | void {
-  const arr = assertArray(loc, value);
-  if (arr) {
-    arr.forEach((item, i) => assertIgnoreItem(access(loc, i), item));
-  }
-  return (arr: any);
+function createArrayAssertion<T>(
+  assertValid: (loc: GeneralPath, value: mixed) => T,
+): (loc: GeneralPath, value: mixed) => $ReadOnlyArray<T> | void {
+  return (loc, value) => {
+    const arr = assertArray(loc, value);
+    if (arr) arr.forEach((item, i) => assertValid(access(loc, i), item));
+    return (arr: any);
+  };
 }
-function assertIgnoreItem(loc: GeneralPath, value: mixed): IgnoreItem {
+
+export const assertIgnoreList = createArrayAssertion(function assertIgnoreItem(
+  loc: GeneralPath,
+  value: mixed,
+): IgnoreItem {
   if (
     typeof value !== "string" &&
     typeof value !== "function" &&
@@ -240,7 +243,26 @@ function assertIgnoreItem(loc: GeneralPath, value: mixed): IgnoreItem {
     );
   }
   return value;
-}
+});
+
+export const assertExtensionsList = createArrayAssertion(
+  function assertExtension(
+    loc: GeneralPath,
+    value: mixed,
+  ): FileExtension | "*" {
+    if (value === "*") return value;
+
+    if (typeof value !== "string") {
+      throw new Error(
+        `${msg(loc)} must be an array of string values, or undefined`,
+      );
+    }
+    if (!value.startsWith(".")) {
+      throw new Error(`${msg(loc)} must start with a '.' (dot)`);
+    }
+    return (value: any);
+  },
+);
 
 export function assertConfigApplicableTest(
   loc: OptionPath,

packages/babel-core/src/config/validation/options.js

@@ -14,6 +14,7 @@ import {
   assertCallerMetadata,
   assertInputSourceMap,
   assertIgnoreList,
+  assertExtensionsList,
   assertPluginList,
   assertConfigApplicableTest,
   assertConfigFileSearch,
@@ -114,6 +115,10 @@ const COMMON_VALIDATORS: ValidatorSet = {
     $PropertyType<ValidatedOptions, "exclude">,
   >),
 
+  extensions: (assertExtensionsList: Validator<
+    $PropertyType<ValidatedOptions, "extensions">,
+  >),
+
   retainLines: (assertBoolean: Validator<
     $PropertyType<ValidatedOptions, "retainLines">,
   >),
@@ -195,9 +200,12 @@ export type ValidatedOptions = {
 
   extends?: string,
   env?: EnvSet<ValidatedOptions>,
+  overrides?: OverridesList,
+
+  // Options to enable/disable processing of some files
   ignore?: IgnoreList,
   only?: IgnoreList,
-  overrides?: OverridesList,
+  extensions?: ExtensionsList,
 
   // Generally verify if a given config object should be applied to the given file.
   test?: ConfigApplicableTest,
@@ -252,6 +260,9 @@ export type EnvSet<T> = {
 export type IgnoreItem = string | Function | RegExp;
 export type IgnoreList = $ReadOnlyArray<IgnoreItem>;
 
+export opaque type FileExtension = string;
+export type ExtensionsList = $ReadOnlyArray<FileExtension | "*">;
+
 export type PluginOptions = {} | void | false;
 export type PluginTarget = string | {} | Function;
 export type PluginItem =

packages/babel-core/src/index.js

@@ -1,5 +1,7 @@
 // @flow
 
+import type { ExtensionsList } from "./config/validation/options";
+
 export { default as File } from "./transformation/file/file";
 export { default as buildExternalHelpers } from "./tools/build-external-helpers";
 export { resolvePlugin, resolvePreset } from "./config/files";
@@ -41,13 +43,9 @@ export { parse, parseSync, parseAsync } from "./parse";
  * Recommended set of compilable extensions. Not used in @babel/core directly, but meant as
  * as an easy source for tooling making use of @babel/core.
  */
-export const DEFAULT_EXTENSIONS = Object.freeze([
-  ".js",
-  ".jsx",
-  ".es6",
-  ".es",
-  ".mjs",
-]);
+export const DEFAULT_EXTENSIONS: ExtensionsList = Object.freeze(
+  ([".js", ".jsx", ".es6", ".es", ".mjs"]: any),
+);
 
 // For easier backward-compatibility, provide an API like the one we exposed in Babel 6.
 import { loadOptions } from "./config";