Pass "targets" to plugins and presets

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";
@@ -204,7 +204,7 @@ 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" }]`
@@ -230,7 +242,7 @@ const loadDescriptor = makeWeakCache(function* (
   if (typeof value === "function") {
     const api = {
       ...context,
-      ...makeAPI(cache),
+      ...makePluginAPI(cache),
     };
     try {
       item = value(api, options, dirname);
@@ -368,7 +380,7 @@ 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/test/fixtures/plugins/targets/plugin/input.js

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

packages/babel-core/test/fixtures/plugins/targets/plugin/options.json

@@ -0,0 +1,4 @@
+{
+  "targets": ["firefox 64", "node 8"],
+  "plugins": ["./plugin"]
+}

packages/babel-core/test/fixtures/plugins/targets/plugin/output.js

@@ -0,0 +1,2 @@
+;
+"plugin: {\"firefox\":\"64.0.0\",\"node\":\"8.17.0\"}"

packages/babel-core/test/fixtures/plugins/targets/plugin/plugin.js

@@ -0,0 +1,14 @@
+module.exports = function (api) {
+  const { types: t } = api;
+
+  const targets = api.targets();
+
+  return {
+    visitor: {
+      Program(path) {
+        const output = t.stringLiteral(`plugin: ${JSON.stringify(targets)}`);
+        path.pushContainer("body", output);
+      },
+    },
+  };
+};

packages/babel-core/test/fixtures/plugins/targets/preset/input.js

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

packages/babel-core/test/fixtures/plugins/targets/preset/options.json

@@ -0,0 +1,4 @@
+{
+  "targets": ["firefox 64", "node 8"],
+  "presets": ["./preset"]
+}

packages/babel-core/test/fixtures/plugins/targets/preset/output.js

@@ -0,0 +1,2 @@
+;
+"preset: {\"firefox\":\"64.0.0\",\"node\":\"8.17.0\"}"

packages/babel-core/test/fixtures/plugins/targets/preset/preset.js

@@ -0,0 +1,18 @@
+module.exports = function (api) {
+  const targets = api.targets();
+
+  return {
+    plugins: [plugin],
+  };
+
+  function plugin({ types: t }) {
+    return {
+      visitor: {
+        Program(path) {
+          const output = t.stringLiteral(`preset: ${JSON.stringify(targets)}`);
+          path.pushContainer("body", output);
+        },
+      },
+    };
+  }
+};