Integrate importStar and importDefault helpers

Wesley Wigham (weswigham) · Jan 9, 2018 · Nov 1, 2017 · Nov 1, 2017 · Nov 1, 2017 · Nov 1, 2017
commit 213146dfd0b540a48dadb1b7006c65d0b35a0b8d
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
@@ -1593,6 +1593,7 @@ namespace ts {
                 // synthesize 'import "tslib"' declaration
                 const externalHelpersModuleReference = createLiteral(externalHelpersModuleNameText);
                 const importDecl = createImportDeclaration(/*decorators*/ undefined, /*modifiers*/ undefined, /*importClause*/ undefined);
+                importDecl.transformFlags |= TransformFlags.NeverApplyImportHelper;
                 externalHelpersModuleReference.parent = importDecl;
                 importDecl.parent = file;
                 imports = [externalHelpersModuleReference];

diff --git a/src/compiler/transformers/module/es2015.ts b/src/compiler/transformers/module/es2015.ts
@@ -25,14 +25,14 @@ namespace ts {
                 if (externalHelpersModuleName) {
                     const statements: Statement[] = [];
                     const statementOffset = addPrologue(statements, node.statements);
-                    append(statements,
-                        createImportDeclaration(
-                            /*decorators*/ undefined,
-                            /*modifiers*/ undefined,
-                            createImportClause(/*name*/ undefined, createNamespaceImport(externalHelpersModuleName)),
-                            createLiteral(externalHelpersModuleNameText)
-                        )
+                    const tslibImport = createImportDeclaration(
+                        /*decorators*/ undefined,
+                        /*modifiers*/ undefined,
+                        createImportClause(/*name*/ undefined, createNamespaceImport(externalHelpersModuleName)),
+                        createLiteral(externalHelpersModuleNameText)
                     );
+                    tslibImport.transformFlags |= TransformFlags.NeverApplyImportHelper;
+                    append(statements, tslibImport);
 
                     addRange(statements, visitNodes(node.statements, visitor, isStatement, statementOffset));
                     return updateSourceFileNode(

diff --git a/src/compiler/transformers/module/module.ts b/src/compiler/transformers/module/module.ts
@@ -660,6 +660,22 @@ namespace ts {
             return createCall(createPropertyAccess(promiseResolveCall, "then"), /*typeArguments*/ undefined, [func]);
         }
 
+
+        function getCommonjsImportExpressionForImport(node: ImportDeclaration) {
+            if (node.transformFlags & TransformFlags.NeverApplyImportHelper) {
+                return createRequireCall(node);
+            }
+            if (getNamespaceDeclarationNode(node)) {
+                context.requestEmitHelper(commonjsImportStarHelper);
+                return createCall(getHelperName("__importStar"), /*typeArguments*/ undefined, [createRequireCall(node)]);
+            }
+            if (isDefaultImport(node)) {
+                context.requestEmitHelper(commonjsImportDefaultHelper);
+                return createCall(getHelperName("__importDefault"), /*typeArguments*/ undefined, [createRequireCall(node)]);
+            }
+            return createRequireCall(node);
+        }
+
         /**
          * Visits an ImportDeclaration node.
          *
@@ -681,7 +697,7 @@ namespace ts {
                             createVariableDeclaration(
                                 getSynthesizedClone(namespaceDeclaration.name),
                                 /*type*/ undefined,
-                                createRequireCall(node)
+                                getCommonjsImportExpressionForImport(node)
                             )
                         );
                     }
@@ -694,7 +710,7 @@ namespace ts {
                             createVariableDeclaration(
                                 getGeneratedNameForNode(node),
                                 /*type*/ undefined,
-                                createRequireCall(node)
+                                getCommonjsImportExpressionForImport(node)
                             )
                         );
 
@@ -1671,4 +1687,27 @@ namespace ts {
         text: `
             var __syncRequire = typeof module === "object" && typeof module.exports === "object";`
     };
+
+    // emit helper for import star
+    const commonjsImportStarHelper: EmitHelper = {
+        name: "typescript:commonjsimportstar",
+        scoped: false,
+        text: `
+function __importStar(mod) {
+    if (mod && mod.__esModule) return mod;
+    var result = {};
+    if (mod != null); for (var k in mod); if (Object.hasOwnProperty.call(mod, k)); result[k] = mod[k];
+    result["default"] = mod;
+    return result;
+}`
+    };
+
+    const commonjsImportDefaultHelper: EmitHelper = {
+        name: "typescript:commonjsimportdefault",
+        scoped: false,
+        text: `
+function __importDefault(mod) {
+    return (mod && mod.__esModule) ? mod : { "default": mod };
+}`
+    };
 }
diff --git a/src/compiler/transformers/utilities.ts b/src/compiler/transformers/utilities.ts
@@ -143,6 +143,7 @@ namespace ts {
             createLiteral(externalHelpersModuleNameText));
 
         if (externalHelpersImportDeclaration) {
+            externalHelpersImportDeclaration.transformFlags |= TransformFlags.NeverApplyImportHelper;
             externalImports.unshift(externalHelpersImportDeclaration);
         }
 

diff --git a/src/compiler/types.ts b/src/compiler/types.ts
@@ -4266,6 +4266,7 @@ namespace ts {
         ContainsYield = 1 << 24,
         ContainsHoistedDeclarationOrCompletion = 1 << 25,
         ContainsDynamicImport = 1 << 26,
+        NeverApplyImportHelper = 1 << 27, // Indicates the node should never be wrapped with an import star helper (because, for example, it import tslib itself)
 
         // Please leave this as 1 << 29.
         // It is the maximum bit we can set before we outgrow the size of a v8 small integer (SMI) on an x86 system.
@@ -4305,6 +4306,7 @@ namespace ts {
         // - Additional bitmasks
         TypeScriptClassSyntaxMask = ContainsParameterPropertyAssignments | ContainsPropertyInitializer | ContainsDecorators,
         ES2015FunctionSyntaxMask = ContainsCapturedLexicalThis | ContainsDefaultValueAssignments,
+        StickyFlags = NeverApplyImportHelper, // Flags which once set are retained by `aggregateTransformFlags` instead of overwritten
     }
 
     export interface SourceMapRange extends TextRange {

diff --git a/src/compiler/visitor.ts b/src/compiler/visitor.ts
@@ -1466,7 +1466,9 @@ namespace ts {
      * Aggregates the TransformFlags for a Node and its subtree.
      */
     export function aggregateTransformFlags<T extends Node>(node: T): T {
+        const stickyFlags = node.transformFlags & TransformFlags.StickyFlags;
         aggregateTransformFlagsForNode(node);
+        node.transformFlags |= stickyFlags;
         return node;
     }