Merge pull request #7972 from Microsoft/exportStarOfNonValues

emit export star only if export will yield anything with value side

src/compiler/transformers/module/es6.ts

@@ -23,6 +23,8 @@ namespace ts {
             switch (node.kind) {
                 case SyntaxKind.ImportDeclaration:
                     return visitImportDeclaration(<ImportDeclaration>node);
+                case SyntaxKind.ImportEqualsDeclaration:
+                    return visitImportEqualsDeclaration(<ImportEqualsDeclaration>node);
                 case SyntaxKind.ImportClause:
                     return visitImportClause(<ImportClause>node);
                 case SyntaxKind.NamedImports:
@@ -30,11 +32,25 @@ namespace ts {
                     return visitNamedBindings(<NamedImportBindings>node);
                 case SyntaxKind.ImportSpecifier:
                     return visitImportSpecifier(<ImportSpecifier>node);
+                case SyntaxKind.ExportAssignment:
+                    return visitExportAssignment(<ExportAssignment>node);
             }
 
             return node;
         }
 
+        function visitExportAssignment(node: ExportAssignment): ExportDeclaration {
+            if (node.isExportEquals) {
+                return undefined; // do not emit export equals for ES6
+            }
+            const original = getOriginalNode(node);
+            return nodeIsSynthesized(original) || resolver.isValueAliasDeclaration(original) ? node: undefined;
+        }
+
+        function visitImportEqualsDeclaration(node: ImportEqualsDeclaration): ImportEqualsDeclaration {
+            return !isExternalModuleImportEqualsDeclaration(node) || resolver.isReferencedAliasDeclaration(node) ? node : undefined;
+        }
+
         function visitImportDeclaration(node: ImportDeclaration) {
             if (node.importClause) {
                 const newImportClause = visitNode(node.importClause, visitor, isImportClause);

src/compiler/transformers/module/module.ts

@@ -31,7 +31,7 @@ namespace ts {
         let externalImports: (ImportDeclaration | ImportEqualsDeclaration | ExportDeclaration)[];
         let exportSpecifiers: Map<ExportSpecifier[]>;
         let exportEquals: ExportAssignment;
-        let hasExportStars: boolean;
+        let hasExportStarsToExportValues: boolean;
 
         return transformSourceFile;
 
@@ -45,7 +45,7 @@ namespace ts {
                 currentSourceFile = node;
 
                 // Collect information about the external module.
-                ({ externalImports, exportSpecifiers, exportEquals, hasExportStars } = collectExternalModuleInfo(node, resolver));
+                ({ externalImports, exportSpecifiers, exportEquals, hasExportStarsToExportValues } = collectExternalModuleInfo(node, resolver));
 
                 // Perform the transformation.
                 const updated = transformModuleDelegates[moduleKind](node);
@@ -55,7 +55,7 @@ namespace ts {
                 externalImports = undefined;
                 exportSpecifiers = undefined;
                 exportEquals = undefined;
-                hasExportStars = false;
+                hasExportStarsToExportValues = false;
                 return updated;
             }
 
@@ -77,7 +77,7 @@ namespace ts {
             addExportEqualsIfNeeded(statements, /*emitAsReturn*/ false);
 
             const updated = updateSourceFile(node, statements);
-            if (hasExportStars) {
+            if (hasExportStarsToExportValues) {
                 setNodeEmitFlags(updated, NodeEmitFlags.EmitExportStar | getNodeEmitFlags(node));
             }
 
@@ -200,7 +200,7 @@ namespace ts {
             addExportEqualsIfNeeded(statements, /*emitAsReturn*/ true);
 
             const body = createBlock(statements, /*location*/ undefined, /*multiLine*/ true);
-            if (hasExportStars) {
+            if (hasExportStarsToExportValues) {
                 // If we have any `export * from ...` declarations
                 // we need to inform the emitter to add the __export helper.
                 setNodeEmitFlags(body, NodeEmitFlags.EmitExportStar);
@@ -442,7 +442,7 @@ namespace ts {
 
                 return singleOrMany(statements);
             }
-            else {
+            else if (resolver.moduleExportsSomeValue(node.moduleSpecifier)) {
                 // export * from "mod";
                 return createStatement(
                     createCall(

src/compiler/transformers/module/system.ts

@@ -37,7 +37,7 @@ namespace ts {
         let externalImports: (ImportDeclaration | ImportEqualsDeclaration | ExportDeclaration)[];
         let exportSpecifiers: Map<ExportSpecifier[]>;
         let exportEquals: ExportAssignment;
-        let hasExportStars: boolean;
+        let hasExportStarsToExportValues: boolean;
         let exportFunctionForFile: Identifier;
         let contextObjectForFile: Identifier;
         let exportedLocalNames: Identifier[];
@@ -62,7 +62,7 @@ namespace ts {
                 externalImports = undefined;
                 exportSpecifiers = undefined;
                 exportEquals = undefined;
-                hasExportStars = false;
+                hasExportStarsToExportValues = false;
                 exportFunctionForFile = undefined;
                 contextObjectForFile = undefined;
                 exportedLocalNames = undefined;
@@ -89,7 +89,7 @@ namespace ts {
             Debug.assert(!exportFunctionForFile);
 
             // Collect information about the external module and dependency groups.
-            ({ externalImports, exportSpecifiers, exportEquals, hasExportStars } = collectExternalModuleInfo(node, resolver));
+            ({ externalImports, exportSpecifiers, exportEquals, hasExportStarsToExportValues } = collectExternalModuleInfo(node, resolver));
 
             // Make sure that the name of the 'exports' function does not conflict with
             // existing identifiers.
@@ -253,7 +253,7 @@ namespace ts {
         }
 
         function addExportStarIfNeeded(statements: Statement[]) {
-            if (!hasExportStars) {
+            if (!hasExportStarsToExportValues) {
                 return;
             }
             // when resolving exports local exported entries/indirect exported entries in the module

src/compiler/utilities.ts

@@ -2984,7 +2984,7 @@ namespace ts {
         const externalImports: (ImportDeclaration | ImportEqualsDeclaration | ExportDeclaration)[] = [];
         const exportSpecifiers: Map<ExportSpecifier[]> = {};
         let exportEquals: ExportAssignment = undefined;
-        let hasExportStars = false;
+        let hasExportStarsToExportValues = false;
         for (const node of sourceFile.statements) {
             switch (node.kind) {
                 case SyntaxKind.ImportDeclaration:
@@ -3009,8 +3009,10 @@ namespace ts {
                     if ((<ExportDeclaration>node).moduleSpecifier) {
                         if (!(<ExportDeclaration>node).exportClause) {
                             // export * from "mod"
-                            externalImports.push(<ExportDeclaration>node);
-                            hasExportStars = true;
+                            if (resolver.moduleExportsSomeValue((<ExportDeclaration>node).moduleSpecifier)) {
+                                externalImports.push(<ExportDeclaration>node);
+                                hasExportStarsToExportValues = true;
+                            }
                         }
                         else if (resolver.isValueAliasDeclaration(getOriginalNode(node))) {
                             // export { x, y } from "mod" where at least one export is a value symbol
@@ -3040,7 +3042,7 @@ namespace ts {
             }
         }
 
-        return { externalImports, exportSpecifiers, exportEquals, hasExportStars };
+        return { externalImports, exportSpecifiers, exportEquals, hasExportStarsToExportValues };
     }
 
     export function getInitializedVariables(node: VariableDeclarationList) {

tests/baselines/reference/es6ExportEquals.js

@@ -7,7 +7,6 @@ export = f;
 
 //// [es6ExportEquals.js]
 export function f() { }
-export = f;
 
 
 //// [es6ExportEquals.d.ts]