Align behavior with TS

packages/babel-parser/src/plugins/typescript/index.ts

@@ -2017,6 +2017,7 @@ export default (superClass: ClassWithMixin<typeof Parser, IJSXParserMixin>) =>
       // For compatibility to estree we cannot call parseLiteral directly here
       node.expression = super.parseExprAtom() as N.StringLiteral;
       this.expect(tt.parenR);
+      this.sawUnambiguousESM = true;
       return this.finishNode(node, "TSExternalModuleReference");
     }
 
@@ -2711,18 +2712,6 @@ export default (superClass: ClassWithMixin<typeof Parser, IJSXParserMixin>) =>
     */
     checkDuplicateExports() {}
 
-    assertModuleNodeAllowed(node: N.Node): void {
-      if (
-        node.type === "TSImportEqualsDeclaration" ||
-        node.type === "TSExportAssignment"
-      ) {
-        // `import ... =` and `export =` are allowed in scripts,
-        // since they are used for CommonJS.
-        return;
-      }
-      super.assertModuleNodeAllowed(node);
-    }
-
     parseImport(
       node: Undone<N.ImportDeclaration | N.TsImportEqualsDeclaration>,
     ): N.AnyImport {
@@ -2800,6 +2789,7 @@ export default (superClass: ClassWithMixin<typeof Parser, IJSXParserMixin>) =>
         const assign = node as Undone<N.TsExportAssignment>;
         assign.expression = super.parseExpression();
         this.semicolon();
+        this.sawUnambiguousESM = true;
         return this.finishNode(assign, "TSExportAssignment");
       } else if (this.eatContextual(tt._as)) {
         // `export as namespace A;`

packages/babel-parser/test/fixtures/typescript/export/equals-in-script/output.json

@@ -1,6 +1,9 @@
 {
   "type": "File",
   "start":0,"end":11,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":11,"index":11}},
+  "errors": [
+    "SyntaxError: 'import' and 'export' may appear only with 'sourceType: \"module\"' (1:0)"
+  ],
   "program": {
     "type": "Program",
     "start":0,"end":11,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":11,"index":11}},

packages/babel-parser/test/fixtures/typescript/export/equals-in-unambiguous/output.json

@@ -4,7 +4,7 @@
   "program": {
     "type": "Program",
     "start":0,"end":11,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":11,"index":11}},
-    "sourceType": "script",
+    "sourceType": "module",
     "interpreter": null,
     "body": [
       {

packages/babel-parser/test/fixtures/typescript/import/equals-in-script/output.json

@@ -1,6 +1,9 @@
 {
   "type": "File",
   "start":0,"end":15,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":15,"index":15}},
+  "errors": [
+    "SyntaxError: 'import' and 'export' may appear only with 'sourceType: \"module\"' (1:0)"
+  ],
   "program": {
     "type": "Program",
     "start":0,"end":15,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":15,"index":15}},

packages/babel-parser/test/fixtures/typescript/import/equals-require-in-script/output.json

@@ -1,6 +1,9 @@
 {
   "type": "File",
   "start":0,"end":24,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":24,"index":24}},
+  "errors": [
+    "SyntaxError: 'import' and 'export' may appear only with 'sourceType: \"module\"' (1:0)"
+  ],
   "program": {
     "type": "Program",
     "start":0,"end":24,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":24,"index":24}},

packages/babel-parser/test/fixtures/typescript/import/equals-require-in-unambiguous/output.json

@@ -4,7 +4,7 @@
   "program": {
     "type": "Program",
     "start":0,"end":24,"loc":{"start":{"line":1,"column":0,"index":0},"end":{"line":1,"column":24,"index":24}},
-    "sourceType": "script",
+    "sourceType": "module",
     "interpreter": null,
     "body": [
       {

packages/babel-plugin-transform-typescript/src/index.ts

@@ -1,6 +1,6 @@
 import { declare } from "@babel/helper-plugin-utils";
 import syntaxTypeScript from "@babel/plugin-syntax-typescript";
-import type { types as t } from "@babel/core";
+import type { PluginPass, types as t } from "@babel/core";
 import { injectInitialization } from "@babel/helper-create-class-features-plugin";
 import type { Binding, NodePath, Scope } from "@babel/traverse";
 import type { Options as SyntaxOptions } from "@babel/plugin-syntax-typescript";
@@ -78,17 +78,18 @@ function safeRemove(path: NodePath) {
   path.opts.noScope = false;
 }
 
-function assertCjsModuleIsScript(
+function assertCjsTransformEnabled(
   path: NodePath,
+  pass: PluginPass,
   wrong: string,
   suggestion: string,
   extra: string = "",
 ): void {
-  const programParent = path.find(p => p.isProgram()) as NodePath<t.Program>;
-  if (programParent.node.sourceType !== "script") {
+  if (pass.get("@babel/plugin-transform-modules-*") !== "commonjs") {
     throw path.buildCodeFrameError(
-      `\`${wrong}\` is only supported when "sourceType" is "script".\n` +
-        `Please consider using \`${suggestion}\`${extra}.`,
+      `\`${wrong}\` is only supported when compiling modules to CommonJS.\n` +
+        `Please consider using \`${suggestion}\`${extra}, or add ` +
+        `@babel/plugin-transform-modules-commonjs to your Babel config.`,
     );
   }
 }
@@ -589,15 +590,19 @@ export default declare((api, opts: Options) => {
         }
       },
 
-      TSImportEqualsDeclaration(path: NodePath<t.TSImportEqualsDeclaration>) {
+      TSImportEqualsDeclaration(
+        path: NodePath<t.TSImportEqualsDeclaration>,
+        pass,
+      ) {
         const { id, moduleReference } = path.node;
 
         let init: t.Expression;
         let varKind: "var" | "const";
         if (t.isTSExternalModuleReference(moduleReference)) {
           // import alias = require('foo');
-          assertCjsModuleIsScript(
+          assertCjsTransformEnabled(
             path,
+            pass,
             `import ${id.name} = require(...);`,
             `import ${id.name} from '...';`,
             " alongside Typescript's --allowSyntheticDefaultImports option",
@@ -618,9 +623,10 @@ export default declare((api, opts: Options) => {
         path.scope.registerDeclaration(path);
       },
 
-      TSExportAssignment(path) {
-        assertCjsModuleIsScript(
+      TSExportAssignment(path, pass) {
+        assertCjsTransformEnabled(
           path,
+          pass,
           `export = <value>;`,
           `export default <value>;`,
         );

packages/babel-plugin-transform-typescript/test/fixtures/exports/export=/options.json

@@ -1,3 +1,3 @@
 {
-  "throws": "`export = <value>;` is only supported when \"sourceType\" is \"script\".\nPlease consider using `export default <value>;`"
+  "throws": "`export = <value>;` is only supported when compiling modules to CommonJS.\nPlease consider using `export default <value>;`, or add @babel/plugin-transform-modules-commonjs to your Babel config."
 }

packages/babel-plugin-transform-typescript/test/fixtures/imports/import=-module/options.json

@@ -1,4 +1,4 @@
 {
   "sourceType": "module",
-  "throws": "`import lib = require(...);` is only supported when \"sourceType\" is \"script\".\nPlease consider using `import lib from '...';` alongside Typescript's --allowSyntheticDefaultImports option."
+  "throws": "`import lib = require(...);` is only supported when compiling modules to CommonJS.\nPlease consider using `import lib from '...';` alongside Typescript's --allowSyntheticDefaultImports option, or add @babel/plugin-transform-modules-commonjs to your Babel config."
 }