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:^7.12.0",
+    "@babel/helper-compilation-targets": "workspace:^7.12.0",
     "@babel/helper-module-transforms": "workspace:^7.12.0",
     "@babel/helpers": "workspace:^7.10.4",
     "@babel/parser": "workspace:^7.12.0",

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

@@ -3,6 +3,7 @@
 import path from "path";
 import buildDebug from "debug";
 import type { Handler } from "gensync";
+import getTargets from "@babel/helper-compilation-targets";
 import {
   validate,
   type ValidatedOptions,
@@ -678,7 +679,7 @@ function emptyChain(): ConfigChain {
 }
 
 function normalizeOptions(opts: ValidatedOptions): ValidatedOptions {
-  const options = {
+  const options: ValidatedOptions = {
     ...opts,
   };
   delete options.extends;
@@ -699,7 +700,17 @@ function normalizeOptions(opts: ValidatedOptions): ValidatedOptions {
     options.sourceMaps = options.sourceMap;
     delete options.sourceMap;
   }
-  return options;
+
+  const { targets } = options;
+  if (typeof targets === "string") {
+    options.targets = getTargets({ browsers: [targets] });
+  } else if (Array.isArray(targets)) {
+    options.targets = getTargets({ browsers: targets });
+  } else if (targets) {
+    options.targets = getTargets((targets: any));
+  }
+
+  return (options: any);
 }
 
 function dedupDescriptors(

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,
@@ -195,15 +203,15 @@ 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 +1,22 @@
+// @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 };
+  }
+
+  return getTargets((targets: any), {
+    ignoreBrowserslistConfig: true,
+    env: options.browserslistEnv,
+  });
+}

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

@@ -0,0 +1,35 @@
+// @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 };
+  }
+
+  let config;
+  if (typeof options.browserslistConfigFile === "string") {
+    config = path.resolve(root, options.browserslistConfigFile);
+  }
+
+  return getTargets((targets: any), {
+    ignoreBrowserslistConfig: options.browserslistConfigFile === false,
+    config,
+    path: filename ?? root,
+    env: 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) {

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

@@ -1,5 +1,10 @@
 // @flow
 
+import {
+  isBrowsersQueryValid,
+  TargetNames,
+} from "@babel/helper-compilation-targets";
+
 import type {
   ConfigFileSearch,
   BabelrcSearch,
@@ -16,6 +21,7 @@ import type {
   NestingPath,
   CallerMetadata,
   RootMode,
+  TargetsListOrObject,
 } from "./options";
 
 export type { RootPath } from "./options";
@@ -373,3 +379,52 @@ function assertPluginTarget(loc: GeneralPath, value: mixed): PluginTarget {
   }
   return value;
 }
+
+export function assertTargets(
+  loc: GeneralPath,
+  value: mixed,
+): TargetsListOrObject {
+  if (isBrowsersQueryValid(value)) return (value: any);
+
+  if (typeof value !== "object" || !value || Array.isArray(value)) {
+    throw new Error(
+      `${msg(loc)} must be a string, an array of strings or an object`,
+    );
+  }
+
+  assertBrowsersList(access(loc, "browsers"), value.browsers);
+  assertBoolean(access(loc, "esmodules"), value.esmodules);
+
+  for (const key of Object.keys(value)) {
+    const val = value[key];
+    const subLoc = access(loc, key);
+
+    if (key === "esmodules") assertBoolean(subLoc, val);
+    else if (key === "browsers") assertBrowsersList(subLoc, val);
+    else if (!Object.hasOwnProperty.call(TargetNames, key)) {
+      const validTargets = Object.keys(TargetNames).join(", ");
+      throw new Error(
+        `${msg(
+          subLoc,
+        )} is not a valid target. Supported targets are ${validTargets}`,
+      );
+    } else assertBrowserVersion(subLoc, val);
+  }
+
+  return (value: any);
+}
+
+function assertBrowsersList(loc: GeneralPath, value: mixed) {
+  if (value !== undefined && !isBrowsersQueryValid(value)) {
+    throw new Error(
+      `${msg(loc)} must be undefined, a string or an array of strings`,
+    );
+  }
+}
+
+function assertBrowserVersion(loc: GeneralPath, value: mixed) {
+  if (typeof value === "number" && Math.round(value) === value) return;
+  if (typeof value === "string") return;
+
+  throw new Error(`${msg(loc)} must be a string or an integer number`);
+}

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

@@ -1,5 +1,7 @@
 // @flow
 
+import type { InputTargets, Targets } from "@babel/helper-compilation-targets";
+
 import type { ConfigItem } from "../item";
 import Plugin from "../plugin";
 
@@ -23,6 +25,7 @@ import {
   assertSourceMaps,
   assertCompact,
   assertSourceType,
+  assertTargets,
   type ValidatorSet,
   type Validator,
   type OptionPath,
@@ -77,6 +80,16 @@ const NONPRESET_VALIDATORS: ValidatorSet = {
     $PropertyType<ValidatedOptions, "ignore">,
   >),
   only: (assertIgnoreList: Validator<$PropertyType<ValidatedOptions, "only">>),
+
+  targets: (assertTargets: Validator<
+    $PropertyType<ValidatedOptions, "targets">,
+  >),
+  browserslistConfigFile: (assertConfigFileSearch: Validator<
+    $PropertyType<ValidatedOptions, "browserslistConfigFile">,
+  >),
+  browserslistEnv: (assertString: Validator<
+    $PropertyType<ValidatedOptions, "browserslistEnv">,
+  >),
 };
 
 const COMMON_VALIDATORS: ValidatorSet = {
@@ -208,6 +221,11 @@ export type ValidatedOptions = {
   plugins?: PluginList,
   passPerPreset?: boolean,
 
+  // browserslists-related options
+  targets?: TargetsListOrObject,
+  browserslistConfigFile?: ConfigFileSearch,
+  browserslistEnv?: string,
+
   // Options for @babel/generator
   retainLines?: boolean,
   comments?: boolean,
@@ -241,6 +259,11 @@ export type ValidatedOptions = {
   generatorOpts?: {},
 };
 
+export type NormalizedOptions = {
+  ...$Diff<ValidatedOptions, { targets: any }>,
+  +targets: Targets,
+};
+
 export type CallerMetadata = {
   // If 'caller' is specified, require that the name is given for debugging
   // messages.
@@ -273,6 +296,11 @@ export type CompactOption = boolean | "auto";
 export type RootInputSourceMapOption = {} | boolean;
 export type RootMode = "root" | "upward" | "upward-optional";
 
+export type TargetsListOrObject =
+  | Targets
+  | InputTargets
+  | $PropertyType<InputTargets, "browsers">;
+
 export type OptionsSource =
   | "arguments"
   | "configfile"

packages/babel-core/test/config-chain.js

@@ -1004,13 +1004,15 @@ describe("buildConfigChain", function () {
     const getDefaults = () => ({
       babelrc: false,
       configFile: false,
+      browserslistConfigFile: false,
       cwd: process.cwd(),
       root: process.cwd(),
       envName: "development",
       passPerPreset: false,
       plugins: [],
       presets: [],
       cloneInputAst: true,
+      targets: {},
     });
     const realEnv = process.env.NODE_ENV;
     const realBabelEnv = process.env.BABEL_ENV;

packages/babel-core/test/fixtures/targets/.browserslistrc

@@ -0,0 +1,4 @@
+chrome 80
+
+[browserslist-loading-test]
+chrome 70

packages/babel-core/test/fixtures/targets/.browserslistrc-firefox

@@ -0,0 +1 @@
+firefox 74

packages/babel-core/test/fixtures/targets/nested/.browserslistrc

@@ -0,0 +1 @@
+edge 14