Implement constantReexports and enumerableModuleMeta assumptions

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

@@ -333,6 +333,8 @@ export type NestingPath = RootPath | OverridesPath | EnvPath;
 
 export const assumptionsNames = new Set<string>([
   "arrayLikeIsIterable",
+  "constantReexports",
+  "enumerableModuleMeta",
   "ignoreFunctionLength",
   "ignoreToPrimitiveHint",
   "iterableIsArray",

packages/babel-helper-module-transforms/src/index.js

@@ -27,22 +27,27 @@ export { hasExports, isSideEffectImport, isModule, rewriteThis };
 export function rewriteModuleStatementsAndPrepareHeader(
   path: NodePath,
   {
+    // TODO(Babel 8): Remove this
+    loose,
+
     exportName,
     strict,
     allowTopLevelThis,
     strictMode,
-    loose,
     noInterop,
     lazy,
     esNamespaceOnly,
+
+    constantReexports = loose,
+    enumerableModuleMeta = loose,
   },
 ) {
   assert(isModule(path), "Cannot process module statements in a script");
   path.node.sourceType = "script";
 
   const meta = normalizeAndLoadModuleMetadata(path, exportName, {
     noInterop,
-    loose,
+    initializeReexports: constantReexports,
     lazy,
     esNamespaceOnly,
   });
@@ -67,7 +72,7 @@ export function rewriteModuleStatementsAndPrepareHeader(
 
   const headers = [];
   if (hasExports(meta) && !strict) {
-    headers.push(buildESModuleHeader(meta, loose /* enumerable */));
+    headers.push(buildESModuleHeader(meta, enumerableModuleMeta));
   }
 
   const nameList = buildExportNameListDeclaration(path, meta);
@@ -78,7 +83,9 @@ export function rewriteModuleStatementsAndPrepareHeader(
   }
 
   // Create all of the statically known named exports.
-  headers.push(...buildExportInitializationStatements(path, meta, loose));
+  headers.push(
+    ...buildExportInitializationStatements(path, meta, constantReexports),
+  );
 
   return { meta, headers };
 }
@@ -128,7 +135,7 @@ export function wrapInterop(
 export function buildNamespaceInitStatements(
   metadata: ModuleMetadata,
   sourceMetadata: SourceModuleMetadata,
-  loose: boolean = false,
+  constantReexports: boolean = false,
 ) {
   const statements = [];
 
@@ -146,8 +153,8 @@ export function buildNamespaceInitStatements(
       }),
     );
   }
-  if (loose) {
-    statements.push(...buildReexportsFromMeta(metadata, sourceMetadata, loose));
+  if (constantReexports) {
+    statements.push(...buildReexportsFromMeta(metadata, sourceMetadata, true));
   }
   for (const exportName of sourceMetadata.reexportNamespace) {
     // Assign export to namespace object.
@@ -172,7 +179,7 @@ export function buildNamespaceInitStatements(
     const statement = buildNamespaceReexport(
       metadata,
       t.cloneNode(srcNamespace),
-      loose,
+      constantReexports,
     );
     statement.loc = sourceMetadata.reexportAll.loc;
 
@@ -183,8 +190,8 @@ export function buildNamespaceInitStatements(
 }
 
 const ReexportTemplate = {
-  loose: template.statement`EXPORTS.EXPORT_NAME = NAMESPACE_IMPORT;`,
-  looseComputed: template.statement`EXPORTS["EXPORT_NAME"] = NAMESPACE_IMPORT;`,
+  constant: template.statement`EXPORTS.EXPORT_NAME = NAMESPACE_IMPORT;`,
+  constantComputed: template.statement`EXPORTS["EXPORT_NAME"] = NAMESPACE_IMPORT;`,
   spec: template`
     Object.defineProperty(EXPORTS, "EXPORT_NAME", {
       enumerable: true,
@@ -198,7 +205,7 @@ const ReexportTemplate = {
 const buildReexportsFromMeta = (
   meta: ModuleMetadata,
   metadata: SourceModuleMetadata,
-  loose,
+  constantReexports: boolean,
 ) => {
   const namespace = metadata.lazy
     ? t.callExpression(t.identifier(metadata.name), [])
@@ -224,11 +231,11 @@ const buildReexportsFromMeta = (
       EXPORT_NAME: exportName,
       NAMESPACE_IMPORT,
     };
-    if (loose) {
+    if (constantReexports) {
       if (stringSpecifiers.has(exportName)) {
-        return ReexportTemplate.looseComputed(astNodes);
+        return ReexportTemplate.constantComputed(astNodes);
       } else {
-        return ReexportTemplate.loose(astNodes);
+        return ReexportTemplate.constant(astNodes);
       }
     } else {
       return ReexportTemplate.spec(astNodes);
@@ -241,9 +248,9 @@ const buildReexportsFromMeta = (
  */
 function buildESModuleHeader(
   metadata: ModuleMetadata,
-  enumerable: boolean = false,
+  enumerableModuleMeta: boolean = false,
 ) {
-  return (enumerable
+  return (enumerableModuleMeta
     ? template.statement`
         EXPORTS.__esModule = true;
       `
@@ -257,8 +264,8 @@ function buildESModuleHeader(
 /**
  * Create a re-export initialization loop for a specific imported namespace.
  */
-function buildNamespaceReexport(metadata, namespace, loose) {
-  return (loose
+function buildNamespaceReexport(metadata, namespace, constantReexports) {
+  return (constantReexports
     ? template.statement`
         Object.keys(NAMESPACE).forEach(function(key) {
           if (key === "default" || key === "__esModule") return;
@@ -347,7 +354,7 @@ function buildExportNameListDeclaration(
 function buildExportInitializationStatements(
   programPath: NodePath,
   metadata: ModuleMetadata,
-  loose: boolean = false,
+  constantReexports: boolean = false,
 ) {
   const initStatements = [];
 
@@ -365,8 +372,8 @@ function buildExportInitializationStatements(
   }
 
   for (const data of metadata.source.values()) {
-    if (!loose) {
-      initStatements.push(...buildReexportsFromMeta(metadata, data, loose));
+    if (!constantReexports) {
+      initStatements.push(...buildReexportsFromMeta(metadata, data, false));
     }
     for (const exportName of data.reexportNamespace) {
       exportNames.push(exportName);

packages/babel-helper-module-transforms/src/normalize-and-load-metadata.js

@@ -86,7 +86,7 @@ export default function normalizeModuleAndLoadMetadata(
   exportName?: string,
   {
     noInterop = false,
-    loose = false,
+    initializeReexports = false,
     lazy = false,
     esNamespaceOnly = false,
   } = {},
@@ -100,10 +100,7 @@ export default function normalizeModuleAndLoadMetadata(
 
   const { local, source, hasExports } = getModuleMetadata(
     programPath,
-    {
-      loose,
-      lazy,
-    },
+    { initializeReexports, lazy },
     stringSpecifiers,
   );
 
@@ -170,12 +167,15 @@ function getExportSpecifierName(
  */
 function getModuleMetadata(
   programPath: NodePath,
-  { loose, lazy }: { loose: boolean, lazy: boolean },
+  {
+    lazy,
+    initializeReexports,
+  }: { lazy: boolean, initializeReexports: boolean },
   stringSpecifiers: Set<string>,
 ) {
   const localData = getLocalExportMetadata(
     programPath,
-    loose,
+    initializeReexports,
     stringSpecifiers,
   );
 
@@ -361,7 +361,7 @@ function getModuleMetadata(
  */
 function getLocalExportMetadata(
   programPath: NodePath,
-  loose: boolean,
+  initializeReexports: boolean,
   stringSpecifiers: Set<string>,
 ): Map<string, LocalExportMetadata> {
   const bindingKindLookup = new Map();
@@ -376,7 +376,7 @@ function getLocalExportMetadata(
         if (child.node.declaration) {
           child = child.get("declaration");
         } else if (
-          loose &&
+          initializeReexports &&
           child.node.source &&
           child.get("source").isStringLiteral()
         ) {
@@ -429,7 +429,10 @@ function getLocalExportMetadata(
   };
 
   programPath.get("body").forEach(child => {
-    if (child.isExportNamedDeclaration() && (loose || !child.node.source)) {
+    if (
+      child.isExportNamedDeclaration() &&
+      (initializeReexports || !child.node.source)
+    ) {
       if (child.node.declaration) {
         const declaration = child.get("declaration");
         const ids = declaration.getOuterBindingIdentifierPaths();

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

@@ -38,7 +38,13 @@ function injectWrapper(path, wrapper) {
 export default declare((api, options) => {
   api.assertVersion(7);
 
-  const { loose, allowTopLevelThis, strict, strictMode, noInterop } = options;
+  const { allowTopLevelThis, strict, strictMode, noInterop } = options;
+
+  const constantReexports =
+    api.assumption("constantReexports") ?? options.loose;
+  const enumerableModuleMeta =
+    api.assumption("enumerableModuleMeta") ?? options.loose;
+
   return {
     name: "transform-modules-amd",
 
@@ -103,7 +109,8 @@ export default declare((api, options) => {
           const { meta, headers } = rewriteModuleStatementsAndPrepareHeader(
             path,
             {
-              loose,
+              enumerableModuleMeta,
+              constantReexports,
               strict,
               strictMode,
               allowTopLevelThis,
@@ -141,7 +148,11 @@ export default declare((api, options) => {
             }
 
             headers.push(
-              ...buildNamespaceInitStatements(meta, metadata, loose),
+              ...buildNamespaceInitStatements(
+                meta,
+                metadata,
+                constantReexports,
+              ),
             );
           }
 

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

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

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

@@ -0,0 +1,9 @@
+define(["exports", "foo"], function (_exports, _foo) {
+  "use strict";
+
+  Object.defineProperty(_exports, "__esModule", {
+    value: true
+  });
+  _exports.default = void 0;
+  _exports.default = _foo.foo;
+});

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

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

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

@@ -0,0 +1,10 @@
+define(["exports", "foo"], function (_exports, _foo) {
+  "use strict";
+
+  Object.defineProperty(_exports, "__esModule", {
+    value: true
+  });
+  _exports.bar = _exports.default = void 0;
+  _exports.default = _foo.foo;
+  _exports.bar = _foo.bar;
+});

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

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

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

@@ -0,0 +1,9 @@
+define(["exports", "foo"], function (_exports, _foo) {
+  "use strict";
+
+  Object.defineProperty(_exports, "__esModule", {
+    value: true
+  });
+  _exports.bar = void 0;
+  _exports.bar = _foo.foo;
+});

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

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

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

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

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

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

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

@@ -0,0 +1,12 @@
+define(["exports", "foo"], function (_exports, _foo) {
+  "use strict";
+
+  Object.defineProperty(_exports, "__esModule", {
+    value: true
+  });
+  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-amd/test/fixtures/assumption-constantReexports/export-from/input.mjs

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

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

@@ -0,0 +1,9 @@
+define(["exports", "foo"], function (_exports, _foo) {
+  "use strict";
+
+  Object.defineProperty(_exports, "__esModule", {
+    value: true
+  });
+  _exports.foo = void 0;
+  _exports.foo = _foo.foo;
+});

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

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

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

@@ -0,0 +1,8 @@
+define(["exports", "./foo"], function (_exports, _foo) {
+  "use strict";
+
+  Object.defineProperty(_exports, "__esModule", {
+    value: true
+  });
+  _exports.foo = _foo.foo;
+});

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

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

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

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

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

@@ -0,0 +1,8 @@
+define(["exports"], function (_exports) {
+  "use strict";
+
+  _exports.__esModule = true;
+  _exports.foo = void 0;
+  var foo = 2;
+  _exports.foo = foo;
+});

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

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