Pass assumptions set in presets to plugins (#13321)

packages/babel-core/package.json

@@ -66,6 +66,7 @@
   },
   "devDependencies": {
     "@babel/helper-transform-fixture-test-runner": "workspace:*",
+    "@babel/plugin-transform-modules-commonjs": "workspace:*",
     "@types/convert-source-map": "^1.5.1",
     "@types/debug": "^4.1.0",
     "@types/resolve": "^1.3.2",

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

@@ -68,10 +68,9 @@ export default gensync<(inputOpts: unknown) => ResolvedConfig | null>(
       throw new Error("Assertion failure - plugins and presets exist");
     }
 
-    const pluginContext: Context.FullPlugin = {
+    const presetContext: Context.FullPreset = {
       ...context,
       targets: options.targets,
-      assumptions: options.assumptions ?? {},
     };
 
     const toDescriptor = (item: PluginItem) => {
@@ -110,7 +109,7 @@ export default gensync<(inputOpts: unknown) => ResolvedConfig | null>(
                 presets.push({
                   preset: yield* loadPresetDescriptor(
                     descriptor,
-                    pluginContext,
+                    presetContext,
                   ),
                   pass: [],
                 });
@@ -118,7 +117,7 @@ export default gensync<(inputOpts: unknown) => ResolvedConfig | null>(
                 presets.unshift({
                   preset: yield* loadPresetDescriptor(
                     descriptor,
-                    pluginContext,
+                    presetContext,
                   ),
                   pass: pluginDescriptorsPass,
                 });
@@ -168,6 +167,11 @@ export default gensync<(inputOpts: unknown) => ResolvedConfig | null>(
     const opts: any = optionDefaults;
     mergeOptions(opts, options);
 
+    const pluginContext: Context.FullPlugin = {
+      ...presetContext,
+      assumptions: opts.assumptions ?? {},
+    };
+
     yield* enhanceError(context, function* loadPluginDescriptors() {
       pluginDescriptorsByPass[0].unshift(...initialPluginsDescriptors);
 

packages/babel-core/test/assumptions.js

@@ -1,6 +1,7 @@
 import path from "path";
 import { fileURLToPath } from "url";
 import { loadOptions as loadOptionsOrig, transformSync } from "../lib";
+import pluginCommonJS from "@babel/plugin-transform-modules-commonjs";
 
 const cwd = path.dirname(fileURLToPath(import.meta.url));
 
@@ -101,6 +102,63 @@ describe("assumptions", () => {
     expect(assumptionFn).toBeUndefined();
   });
 
+  // https://github.com/babel/babel/issues/13316
+  describe("assumptions set in presets are visible from plugins - #13316", () => {
+    function presetEnumerableModuleMeta() {
+      return { assumptions: { enumerableModuleMeta: true } };
+    }
+
+    function pluginExtractEnumerableModuleMeta(api, options) {
+      options.enumerableModuleMeta = api.assumption("enumerableModuleMeta");
+      return { visitor: {} };
+    }
+
+    it("plugin defined outside preset", () => {
+      const ref = {};
+
+      loadOptions({
+        configFile: false,
+        presets: [presetEnumerableModuleMeta],
+        plugins: [[pluginExtractEnumerableModuleMeta, ref]],
+      });
+
+      expect(ref.enumerableModuleMeta).toBe(true);
+    });
+
+    it("plugin defined inside preset", () => {
+      const ref = {};
+
+      loadOptions({
+        configFile: false,
+        presets: [
+          () => ({
+            assumptions: { enumerableModuleMeta: true },
+            plugins: [[pluginExtractEnumerableModuleMeta, ref]],
+          }),
+        ],
+      });
+
+      expect(ref.enumerableModuleMeta).toBe(true);
+    });
+
+    it("integration", () => {
+      const { code } = transformSync(`export const foo = 1;`, {
+        configFile: false,
+        presets: [presetEnumerableModuleMeta],
+        plugins: [pluginCommonJS],
+      });
+
+      expect(code).toMatchInlineSnapshot(`
+        "\\"use strict\\";
+
+        exports.__esModule = true;
+        exports.foo = void 0;
+        const foo = 1;
+        exports.foo = foo;"
+      `);
+    });
+  });
+
   describe("plugin cache", () => {
     const makePlugin = () =>
       jest.fn(api => {

yarn.lock

@@ -214,6 +214,7 @@ __metadata:
     "@babel/helper-transform-fixture-test-runner": "workspace:*"
     "@babel/helpers": "workspace:^7.14.0"
     "@babel/parser": "workspace:^7.14.2"
+    "@babel/plugin-transform-modules-commonjs": "workspace:*"
     "@babel/template": "workspace:^7.12.13"
     "@babel/traverse": "workspace:^7.14.2"
     "@babel/types": "workspace:^7.14.2"