Implement assumptions defined in the babel/rfcs#5 RFC

- `mutableTemplateObject` and `ignoreToPrimitiveHint` (#12408)
- `setClassMethods` (#12407)
- `setComputedProperties` (#12490)
- `ignoreFunctionLength` (#12491)
- `noDocumentAll` (#12481)
- `iterableIsArray` and `arrayLikeIsIterable` (#12489)
- `pureGetters` (#12504)
- `skipForOfIteratorClosing` (#12496)
- `objectRestNoSymbols`, `setSpreadProperties` and `pureGetters` (#12505)
- `noNewArrows` (#12613, #12793)
- `setPublicClassFields` and `privateFieldsAsProperties` (#12497)
- `constantReexports` and `enumerableModuleMeta` (#12618)
- `constantSuper`, `superIsCallableConstructor` and `noClassCalls` (#12726)

Co-authored-by: Justin Ridgewell <justin@ridgewell.name>
Co-authored-by: Huáng Jùnliàng <JLHwung@users.noreply.github.com>

packages/babel-plugin-transform-modules-commonjs/src/index.js

@@ -19,8 +19,6 @@ export default declare((api, options) => {
   const transformImportCall = createDynamicImportTransform(api);
 
   const {
-    loose,
-
     // 'true' for non-mjs files to strictly have .default, instead of having
     // destructuring-like behavior for their properties.
     strictNamespace = false,
@@ -37,6 +35,11 @@ export default declare((api, options) => {
     allowCommonJSExports = true,
   } = options;
 
+  const constantReexports =
+    api.assumption("constantReexports") ?? options.loose;
+  const enumerableModuleMeta =
+    api.assumption("enumerableModuleMeta") ?? options.loose;
+
   if (
     typeof lazy !== "boolean" &&
     typeof lazy !== "function" &&
@@ -169,7 +172,8 @@ export default declare((api, options) => {
             path,
             {
               exportName: "exports",
-              loose,
+              constantReexports,
+              enumerableModuleMeta,
               strict,
               strictMode,
               allowTopLevelThis,
@@ -215,7 +219,11 @@ export default declare((api, options) => {
 
             headers.push(header);
             headers.push(
-              ...buildNamespaceInitStatements(meta, metadata, loose),
+              ...buildNamespaceInitStatements(
+                meta,
+                metadata,
+                constantReexports,
+              ),
             );
           }
 

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/export-from-2/input.mjs

@@ -0,0 +1 @@
+export {foo as default} from "foo";

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/export-from-2/output.js

@@ -0,0 +1,10 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = void 0;
+
+var _foo = require("foo");
+
+exports.default = _foo.foo;

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/export-from-3/input.mjs

@@ -0,0 +1 @@
+export {foo as default, bar} from "foo";

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/export-from-3/output.js

@@ -0,0 +1,11 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.bar = exports.default = void 0;
+
+var _foo = require("foo");
+
+exports.default = _foo.foo;
+exports.bar = _foo.bar;

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/export-from-4/input.mjs

@@ -0,0 +1 @@
+export {foo as bar} from "foo";

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/export-from-4/output.js

@@ -0,0 +1,10 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.bar = void 0;
+
+var _foo = require("foo");
+
+exports.bar = _foo.foo;

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/export-from-5/input.mjs

@@ -0,0 +1 @@
+export {foo, bar} from "foo";

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/export-from-5/output.js

@@ -0,0 +1,11 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.bar = exports.foo = void 0;
+
+var _foo = require("foo");
+
+exports.foo = _foo.foo;
+exports.bar = _foo.bar;

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/export-from-6/input.mjs

@@ -0,0 +1 @@
+export * from "foo";

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/export-from-6/output.js

@@ -0,0 +1,13 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+
+var _foo = require("foo");
+
+Object.keys(_foo).forEach(function (key) {
+  if (key === "default" || key === "__esModule") return;
+  if (key in exports && exports[key] === _foo[key]) return;
+  exports[key] = _foo[key];
+});

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/export-from/input.mjs

@@ -0,0 +1 @@
+export {foo} from "foo";

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/export-from/output.js

@@ -0,0 +1,10 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.foo = void 0;
+
+var _foo = require("foo");
+
+exports.foo = _foo.foo;

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/import-export/input.mjs

@@ -0,0 +1,3 @@
+import { foo } from "./foo";
+
+export { foo };

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/import-export/output.js

@@ -0,0 +1,9 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+
+var _foo = require("./foo");
+
+exports.foo = _foo.foo;

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-constantReexports/options.json

@@ -0,0 +1,6 @@
+{
+  "assumptions": {
+    "constantReexports": true
+  },
+  "plugins": ["external-helpers", "transform-modules-commonjs"]
+}

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-enumerableModuleMeta/export/input.mjs

@@ -0,0 +1 @@
+export var foo = 2;

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-enumerableModuleMeta/export/output.js

@@ -0,0 +1,6 @@
+"use strict";
+
+exports.__esModule = true;
+exports.foo = void 0;
+var foo = 2;
+exports.foo = foo;

packages/babel-plugin-transform-modules-commonjs/test/fixtures/assumption-enumerableModuleMeta/options.json

@@ -0,0 +1,6 @@
+{
+  "assumptions": {
+    "enumerableModuleMeta": true
+  },
+  "plugins": ["external-helpers", "transform-modules-commonjs"]
+}