Preserve module marker in es2015+ module emit for tool compatability (microsoft#38712)

Author: weswigham

src/compiler/transformers/module/esnextAnd2015.ts

@@ -18,25 +18,36 @@ namespace ts {
             }
 
             if (isExternalModule(node) || compilerOptions.isolatedModules) {
-                const externalHelpersImportDeclaration = createExternalHelpersImportDeclarationIfNeeded(node, compilerOptions);
-                if (externalHelpersImportDeclaration) {
-                    const statements: Statement[] = [];
-                    const statementOffset = addPrologue(statements, node.statements);
-                    append(statements, externalHelpersImportDeclaration);
-
-                    addRange(statements, visitNodes(node.statements, visitor, isStatement, statementOffset));
-                    return updateSourceFileNode(
-                        node,
-                        setTextRange(createNodeArray(statements), node.statements));
-                }
-                else {
-                    return visitEachChild(node, visitor, context);
+                const result = updateExternalModule(node);
+                if (!isExternalModule(node) || some(result.statements, isExternalModuleIndicator)) {
+                    return result;
                 }
+                return updateSourceFileNode(
+                    result,
+                    setTextRange(createNodeArray([...result.statements, createEmptyExports()]), result.statements),
+                );
             }
 
             return node;
         }
 
+        function updateExternalModule(node: SourceFile) {
+            const externalHelpersImportDeclaration = createExternalHelpersImportDeclarationIfNeeded(node, compilerOptions);
+            if (externalHelpersImportDeclaration) {
+                const statements: Statement[] = [];
+                const statementOffset = addPrologue(statements, node.statements);
+                append(statements, externalHelpersImportDeclaration);
+
+                addRange(statements, visitNodes(node.statements, visitor, isStatement, statementOffset));
+                return updateSourceFileNode(
+                    node,
+                    setTextRange(createNodeArray(statements), node.statements));
+            }
+            else {
+                return visitEachChild(node, visitor, context);
+            }
+        }
+
         function visitor(node: Node): VisitResult<Node> {
             switch (node.kind) {
                 case SyntaxKind.ImportEqualsDeclaration:

tests/baselines/reference/asyncAwaitIsolatedModules_es2017.js

@@ -71,3 +71,4 @@ var M;
     async function f1() { }
     M.f1 = f1;
 })(M || (M = {}));
+export {};

tests/baselines/reference/asyncAwaitIsolatedModules_es6.js

@@ -112,3 +112,4 @@ var M;
     }
     M.f1 = f1;
 })(M || (M = {}));
+export {};

tests/baselines/reference/computedPropertyName.js

@@ -65,3 +65,4 @@ class F {
 }
 class G {
 }
+export {};

tests/baselines/reference/decoratedClassFromExternalModule.js

@@ -27,3 +27,4 @@ let Decorated = /** @class */ (() => {
 })();
 export default Decorated;
 //// [undecorated.js]
+export {};

tests/baselines/reference/es6ExportAssignment.js

@@ -4,3 +4,4 @@ export = a;
 
 //// [es6ExportAssignment.js]
 var a = 10;
+export {};

tests/baselines/reference/es6ExportAssignment2.js

@@ -10,4 +10,6 @@ import * as a from "a";
 
 //// [a.js]
 var a = 10;
+export {};
 //// [b.js]
+export {};

tests/baselines/reference/es6ExportAssignment3.js

@@ -9,3 +9,4 @@ import * as a from "a";
 
 
 //// [b.js]
+export {};

tests/baselines/reference/es6ExportAssignment4.js

@@ -11,3 +11,4 @@ import * as a from "a";
 
 
 //// [b.js]
+export {};

tests/baselines/reference/es6ImportEqualsDeclaration.js

@@ -9,4 +9,6 @@ import a = require("server");
 
 //// [server.js]
 var a = 10;
+export {};
 //// [client.js]
+export {};