Expose an api.caller(...) handler for presets to access caller metadata.

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

@@ -144,9 +144,14 @@ export function buildRootChain(
 
   let configFile;
   if (typeof opts.configFile === "string") {
-    configFile = loadConfig(opts.configFile, context.cwd, context.envName);
+    configFile = loadConfig(
+      opts.configFile,
+      context.cwd,
+      context.envName,
+      context.caller,
+    );
   } else if (opts.configFile !== false) {
-    configFile = findRootConfig(context.root, context.envName);
+    configFile = findRootConfig(context.root, context.envName, context.caller);
   }
 
   let { babelrc, babelrcRoots } = opts;
@@ -465,7 +470,12 @@ function mergeExtendsChain(
 ): boolean {
   if (opts.extends === undefined) return true;
 
-  const file = loadConfig(opts.extends, dirname, context.envName);
+  const file = loadConfig(
+    opts.extends,
+    dirname,
+    context.envName,
+    context.caller,
+  );
 
   if (files.has(file)) {
     throw new Error(

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

@@ -14,6 +14,7 @@ import makeAPI from "../helpers/config-api";
 import { makeStaticFileCache } from "./utils";
 import pathPatternToRegex from "../pattern-to-regex";
 import type { FilePackageData, RelativeConfig, ConfigFile } from "./types";
+import type { CallerMetadata } from "../validation/options";
 
 const debug = buildDebug("babel:config:loading:files:configuration");
 
@@ -26,6 +27,7 @@ const BABELIGNORE_FILENAME = ".babelignore";
 export function findRelativeConfig(
   packageData: FilePackageData,
   envName: string,
+  caller: CallerMetadata | void,
 ): RelativeConfig {
   let config = null;
   let ignore = null;
@@ -37,7 +39,7 @@ export function findRelativeConfig(
       config = [BABELRC_FILENAME, BABELRC_JS_FILENAME].reduce(
         (previousConfig: ConfigFile | null, name) => {
           const filepath = path.join(loc, name);
-          const config = readConfig(filepath, envName);
+          const config = readConfig(filepath, envName, caller);
 
           if (config && previousConfig) {
             throw new Error(
@@ -91,10 +93,11 @@ export function findRelativeConfig(
 export function findRootConfig(
   dirname: string,
   envName: string,
+  caller: CallerMetadata | void,
 ): ConfigFile | null {
   const filepath = path.resolve(dirname, BABEL_CONFIG_JS_FILENAME);
 
-  const conf = readConfig(filepath, envName);
+  const conf = readConfig(filepath, envName, caller);
   if (conf) {
     debug("Found root config %o in $o.", BABEL_CONFIG_JS_FILENAME, dirname);
   }
@@ -105,10 +108,11 @@ export function loadConfig(
   name: string,
   dirname: string,
   envName: string,
+  caller: CallerMetadata | void,
 ): ConfigFile {
   const filepath = resolve.sync(name, { basedir: dirname });
 
-  const conf = readConfig(filepath, envName);
+  const conf = readConfig(filepath, envName, caller);
   if (!conf) {
     throw new Error(`Config file ${filepath} contains no configuration data`);
   }
@@ -121,16 +125,22 @@ export function loadConfig(
  * Read the given config file, returning the result. Returns null if no config was found, but will
  * throw if there are parsing errors while loading a config.
  */
-function readConfig(filepath, envName): ConfigFile | null {
+function readConfig(filepath, envName, caller): ConfigFile | null {
   return path.extname(filepath) === ".js"
-    ? readConfigJS(filepath, { envName })
+    ? readConfigJS(filepath, { envName, caller })
     : readConfigJSON5(filepath);
 }
 
 const LOADING_CONFIGS = new Set();
 
 const readConfigJS = makeStrongCache(
-  (filepath, cache: CacheConfigurator<{ envName: string }>) => {
+  (
+    filepath,
+    cache: CacheConfigurator<{
+      envName: string,
+      caller: CallerMetadata | void,
+    }>,
+  ) => {
     if (!fs.existsSync(filepath)) {
       cache.forever();
       return null;

packages/babel-core/src/config/files/index-browser.js

@@ -7,6 +7,8 @@ import type {
   FilePackageData,
 } from "./types";
 
+import type { CallerMetadata } from "../validation/options";
+
 export type { ConfigFile, IgnoreFile, RelativeConfig, FilePackageData };
 
 export function findPackageData(filepath: string): FilePackageData {
@@ -21,6 +23,7 @@ export function findPackageData(filepath: string): FilePackageData {
 export function findRelativeConfig(
   pkgData: FilePackageData, // eslint-disable-line no-unused-vars
   envName: string, // eslint-disable-line no-unused-vars
+  caller: CallerMetadata | void, // eslint-disable-line no-unused-vars
 ): RelativeConfig {
   return { pkg: null, config: null, ignore: null };
 }
@@ -28,6 +31,7 @@ export function findRelativeConfig(
 export function findRootConfig(
   dirname: string, // eslint-disable-line no-unused-vars
   envName: string, // eslint-disable-line no-unused-vars
+  caller: CallerMetadata | void, // eslint-disable-line no-unused-vars
 ): ConfigFile | null {
   return null;
 }
@@ -36,6 +40,7 @@ export function loadConfig(
   name: string,
   dirname: string,
   envName: string, // eslint-disable-line no-unused-vars
+  caller: CallerMetadata | void, // eslint-disable-line no-unused-vars
 ): ConfigFile {
   throw new Error(`Cannot load ${name} relative to ${dirname} in a browser`);
 }

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

@@ -13,7 +13,7 @@ import {
 import type { UnloadedDescriptor } from "./config-descriptors";
 import traverse from "@babel/traverse";
 import { makeWeakCache, type CacheConfigurator } from "./caching";
-import { validate } from "./validation/options";
+import { validate, type CallerMetadata } from "./validation/options";
 import { validatePluginObject } from "./validation/plugins";
 import makeAPI from "./helpers/config-api";
 
@@ -41,6 +41,7 @@ export type PluginPasses = Array<PluginPassList>;
 // process 'ignore'/'only' and other filename-based logic.
 type SimpleContext = {
   envName: string,
+  caller: CallerMetadata | void,
 };
 
 export default function loadFullConfig(

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

@@ -8,6 +8,8 @@ import {
   type SimpleCacheConfigurator,
 } from "../caching";
 
+import type { CallerMetadata } from "../validation/options";
+
 type EnvFunction = {
   (): string,
   <T>((string) => T): T,
@@ -24,7 +26,7 @@ export type PluginAPI = {
 };
 
 export default function makeAPI(
-  cache: CacheConfigurator<{ envName: string }>,
+  cache: CacheConfigurator<{ envName: string, caller: CallerMetadata | void }>,
 ): PluginAPI {
   const env: any = value =>
     cache.using(data => {
@@ -42,12 +44,16 @@ export default function makeAPI(
       });
     });
 
+  const caller: any = cb =>
+    cache.using(data => assertSimpleType(cb(data.caller)));
+
   return {
     version: coreVersion,
     cache: cache.simple(),
     // Expose ".env()" so people can easily get the same env that we expose using the "env" key.
     env,
     async: () => false,
+    caller,
     assertVersion,
   };
 }