Add targets and browserslist* options to @babel/core

packages/babel-core/package.json

@@ -38,13 +38,16 @@
   },
   "browser": {
     "./lib/config/files/index.js": "./lib/config/files/index-browser.js",
+    "./lib/config/resolve-targets.js": "./lib/config/resolve-targets-browser.js",
     "./lib/transform-file.js": "./lib/transform-file-browser.js",
     "./src/config/files/index.js": "./src/config/files/index-browser.js",
+    "./src/config/resolve-targets.js": "./src/config/resolve-targets-browser.js",
     "./src/transform-file.js": "./src/transform-file-browser.js"
   },
   "dependencies": {
     "@babel/code-frame": "workspace:^7.10.4",
     "@babel/generator": "workspace:^7.12.10",
+    "@babel/helper-compilation-targets": "workspace:^7.12.5",
     "@babel/helper-module-transforms": "workspace:^7.12.1",
     "@babel/helpers": "workspace:^7.12.5",
     "@babel/parser": "workspace:^7.12.10",

packages/babel-core/src/config/files/configuration.js

@@ -9,7 +9,7 @@ import {
   makeWeakCacheSync,
   type CacheConfigurator,
 } from "../caching";
-import makeAPI, { type PluginAPI } from "../helpers/config-api";
+import { makeConfigAPI, type ConfigAPI } from "../helpers/config-api";
 import { makeStaticFileCache } from "./utils";
 import loadCjsOrMjsDefault from "./module-types";
 import pathPatternToRegex from "../pattern-to-regex";
@@ -203,7 +203,7 @@ const readConfigJS = makeStrongCache(function* readConfigJS(
   let assertCache = false;
   if (typeof options === "function") {
     yield* []; // if we want to make it possible to use async configs
-    options = ((options: any): (api: PluginAPI) => {})(makeAPI(cache));
+    options = ((options: any): (api: ConfigAPI) => {})(makeConfigAPI(cache));
 
     assertCache = true;
   }

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

@@ -14,6 +14,7 @@ import {
   type PresetInstance,
 } from "./config-chain";
 import type { UnloadedDescriptor } from "./config-descriptors";
+import type { Targets } from "@babel/helper-compilation-targets";
 import traverse from "@babel/traverse";
 import {
   makeWeakCache,
@@ -27,7 +28,7 @@ import {
   type PluginItem,
 } from "./validation/options";
 import { validatePluginObject } from "./validation/plugins";
-import makeAPI from "./helpers/config-api";
+import { makePluginAPI } from "./helpers/config-api";
 
 import loadPrivatePartialConfig from "./partial";
 import type { ValidatedOptions } from "./validation/options";
@@ -39,6 +40,11 @@ type LoadedDescriptor = {
   alias: string,
 };
 
+type PluginContext = {
+  ...ConfigContext,
+  targets: Targets,
+};
+
 export type { InputOptions } from "./validation/options";
 
 export type ResolvedConfig = {
@@ -55,6 +61,7 @@ export type PluginPasses = Array<PluginPassList>;
 type SimpleContext = {
   envName: string,
   caller: CallerMetadata | void,
+  targets: Targets,
 };
 
 export default gensync<[any], ResolvedConfig | null>(function* loadFullConfig(
@@ -78,6 +85,11 @@ export default gensync<[any], ResolvedConfig | null>(function* loadFullConfig(
     throw new Error("Assertion failure - plugins and presets exist");
   }
 
+  const pluginContext: PluginContext = {
+    ...context,
+    targets: options.targets,
+  };
+
   const toDescriptor = (item: PluginItem) => {
     const desc = getItemDescriptor(item);
     if (!desc) {
@@ -112,12 +124,12 @@ export default gensync<[any], ResolvedConfig | null>(function* loadFullConfig(
             // in the previous pass.
             if (descriptor.ownPass) {
               presets.push({
-                preset: yield* loadPresetDescriptor(descriptor, context),
+                preset: yield* loadPresetDescriptor(descriptor, pluginContext),
                 pass: [],
               });
             } else {
               presets.unshift({
-                preset: yield* loadPresetDescriptor(descriptor, context),
+                preset: yield* loadPresetDescriptor(descriptor, pluginContext),
                 pass: pluginDescriptorsPass,
               });
             }
@@ -172,7 +184,7 @@ export default gensync<[any], ResolvedConfig | null>(function* loadFullConfig(
         const descriptor: UnloadedDescriptor = descs[i];
         if (descriptor.options !== false) {
           try {
-            pass.push(yield* loadPluginDescriptor(descriptor, context));
+            pass.push(yield* loadPluginDescriptor(descriptor, pluginContext));
           } catch (e) {
             if (e.code === "BABEL_UNKNOWN_PLUGIN_PROPERTY") {
               // print special message for `plugins: ["@babel/foo", { foo: "option" }]`
@@ -235,7 +247,7 @@ const loadDescriptor = makeWeakCache(function* (
 
     const api = {
       ...context,
-      ...makeAPI(cache),
+      ...makePluginAPI(cache),
     };
     try {
       item = yield* factory(api, options, dirname);
@@ -375,7 +387,7 @@ const validatePreset = (
  */
 function* loadPresetDescriptor(
   descriptor: UnloadedDescriptor,
-  context: ConfigContext,
+  context: PluginContext,
 ): Handler<ConfigChain | null> {
   const preset = instantiatePreset(yield* loadDescriptor(descriptor, context));
   validatePreset(preset, context, descriptor);

packages/babel-core/src/config/helpers/config-api.js

@@ -1,6 +1,8 @@
 // @flow
 
 import semver from "semver";
+import type { Targets } from "@babel/helper-compilation-targets";
+
 import { version as coreVersion } from "../../";
 import {
   assertSimpleType,
@@ -20,7 +22,9 @@ type EnvFunction = {
 
 type CallerFactory = ((CallerMetadata | void) => mixed) => SimpleType;
 
-export type PluginAPI = {|
+type TargetsFunction = () => Targets;
+
+export type ConfigAPI = {|
   version: string,
   cache: SimpleCacheConfigurator,
   env: EnvFunction,
@@ -29,9 +33,14 @@ export type PluginAPI = {|
   caller?: CallerFactory,
 |};
 
-export default function makeAPI(
-  cache: CacheConfigurator<{ envName: string, caller: CallerMetadata | void }>,
-): PluginAPI {
+export type PluginAPI = {|
+  ...ConfigAPI,
+  targets: TargetsFunction,
+|};
+
+export function makeConfigAPI<
+  SideChannel: { envName: string, caller: CallerMetadata | void },
+>(cache: CacheConfigurator<SideChannel>): ConfigAPI {
   const env: any = value =>
     cache.using(data => {
       if (typeof value === "undefined") return data.envName;
@@ -61,6 +70,22 @@ export default function makeAPI(
   };
 }
 
+export function makePluginAPI(
+  cache: CacheConfigurator<{
+    envName: string,
+    caller: CallerMetadata | void,
+    targets: Targets,
+  }>,
+): PluginAPI {
+  const targets = () =>
+    // We are using JSON.parse/JSON.stringify because it's only possible to cache
+    // primitive values. We can safely stringify the targets object because it
+    // only contains strings as its properties.
+    // Please make the Record and Tuple proposal happen!
+    JSON.parse(cache.using(data => JSON.stringify(data.targets)));
+  return { ...makeConfigAPI(cache), targets };
+}
+
 function assertVersion(range: string | number): void {
   if (typeof range === "number") {
     if (!Number.isInteger(range)) {

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

@@ -14,6 +14,7 @@ import { getEnv } from "./helpers/environment";
 import {
   validate,
   type ValidatedOptions,
+  type NormalizedOptions,
   type RootMode,
 } from "./validation/options";
 
@@ -24,6 +25,7 @@ import {
   type ConfigFile,
   type IgnoreFile,
 } from "./files";
+import { resolveTargets } from "./resolve-targets";
 
 function* resolveRootMode(
   rootDir: string,
@@ -61,7 +63,7 @@ function* resolveRootMode(
 }
 
 type PrivPartialConfig = {
-  options: ValidatedOptions,
+  options: NormalizedOptions,
   context: ConfigContext,
   fileHandling: FileHandling,
   ignore: IgnoreFile | void,
@@ -115,30 +117,36 @@ export default function* loadPrivatePartialConfig(
   const configChain = yield* buildRootChain(args, context);
   if (!configChain) return null;
 
-  const options = {};
+  const merged: ValidatedOptions = {};
   configChain.options.forEach(opts => {
-    mergeOptions(options, opts);
+    mergeOptions((merged: any), opts);
   });
 
-  // 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.
-  options.cloneInputAst = cloneInputAst;
-  options.babelrc = false;
-  options.configFile = false;
-  options.passPerPreset = false;
-  options.envName = context.envName;
-  options.cwd = context.cwd;
-  options.root = context.root;
-  options.filename =
-    typeof context.filename === "string" ? context.filename : undefined;
-
-  options.plugins = configChain.plugins.map(descriptor =>
-    createItemFromDescriptor(descriptor),
-  );
-  options.presets = configChain.presets.map(descriptor =>
-    createItemFromDescriptor(descriptor),
-  );
+  const options: NormalizedOptions = {
+    ...merged,
+    targets: resolveTargets(merged, absoluteRootDir, filename),
+
+    // 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.
+    cloneInputAst,
+    babelrc: false,
+    configFile: false,
+    browserslistConfigFile: false,
+    passPerPreset: false,
+    envName: context.envName,
+    cwd: context.cwd,
+    root: context.root,
+    filename:
+      typeof context.filename === "string" ? context.filename : undefined,
+
+    plugins: configChain.plugins.map(descriptor =>
+      createItemFromDescriptor(descriptor),
+    ),
+    presets: configChain.presets.map(descriptor =>
+      createItemFromDescriptor(descriptor),
+    ),
+  };
 
   return {
     options,
@@ -201,15 +209,15 @@ class PartialConfig {
    * These properties are public, so any changes to them should be considered
    * a breaking change to Babel's API.
    */
-  options: ValidatedOptions;
+  options: NormalizedOptions;
   babelrc: string | void;
   babelignore: string | void;
   config: string | void;
   fileHandling: FileHandling;
   files: Set<string>;
 
   constructor(
-    options: ValidatedOptions,
+    options: NormalizedOptions,
     babelrc: string | void,
     ignore: string | void,
     config: string | void,

packages/babel-core/src/config/resolve-targets-browser.js

@@ -0,0 +1,26 @@
+// @flow
+
+import type { ValidatedOptions } from "./validation/options";
+import getTargets, { type Targets } from "@babel/helper-compilation-targets";
+
+export function resolveTargets(
+  options: ValidatedOptions,
+  // eslint-disable-next-line no-unused-vars
+  root: string,
+  // eslint-disable-next-line no-unused-vars
+  filename: string | void,
+): Targets {
+  let { targets } = options;
+  if (typeof targets === "string" || Array.isArray(targets)) {
+    targets = { browsers: targets };
+  }
+  // $FlowIgnore it thinks that targets.esmodules doesn't exist.
+  if (targets && targets.esmodules) {
+    targets = { ...targets, esmodules: "intersect" };
+  }
+
+  return getTargets((targets: any), {
+    ignoreBrowserslistConfig: true,
+    browserslistEnv: options.browserslistEnv,
+  });
+}

packages/babel-core/src/config/resolve-targets.js

@@ -0,0 +1,39 @@
+// @flow
+
+import typeof * as browserType from "./resolve-targets-browser";
+import typeof * as nodeType from "./resolve-targets";
+
+// Kind of gross, but essentially asserting that the exports of this module are the same as the
+// exports of index-browser, since this file may be replaced at bundle time with index-browser.
+((({}: any): $Exact<browserType>): $Exact<nodeType>);
+
+import type { ValidatedOptions } from "./validation/options";
+import path from "path";
+import getTargets, { type Targets } from "@babel/helper-compilation-targets";
+
+export function resolveTargets(
+  options: ValidatedOptions,
+  root: string,
+  filename: string | void,
+): Targets {
+  let { targets } = options;
+  if (typeof targets === "string" || Array.isArray(targets)) {
+    targets = { browsers: targets };
+  }
+  // $FlowIgnore it thinks that targets.esmodules doesn't exist.
+  if (targets && targets.esmodules) {
+    targets = { ...targets, esmodules: "intersect" };
+  }
+
+  let configFile;
+  if (typeof options.browserslistConfigFile === "string") {
+    configFile = path.resolve(root, options.browserslistConfigFile);
+  }
+
+  return getTargets((targets: any), {
+    ignoreBrowserslistConfig: options.browserslistConfigFile === false,
+    configFile,
+    configPath: filename ?? root,
+    browserslistEnv: options.browserslistEnv,
+  });
+}

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

@@ -1,10 +1,10 @@
 // @flow
 
-import type { ValidatedOptions } from "./validation/options";
+import type { ValidatedOptions, NormalizedOptions } from "./validation/options";
 
 export function mergeOptions(
   target: ValidatedOptions,
-  source: ValidatedOptions,
+  source: ValidatedOptions | NormalizedOptions,
 ): void {
   for (const k of Object.keys(source)) {
     if (k === "parserOpts" && source.parserOpts) {