Handle synthetic nodes correctly as namespace identifiers in system transform

src/compiler/factory.ts

@@ -4318,7 +4318,7 @@ namespace ts {
         const namespaceDeclaration = getNamespaceDeclarationNode(node);
         if (namespaceDeclaration && !isDefaultImport(node)) {
             const name = namespaceDeclaration.name;
-            return isGeneratedIdentifier(name) ? name : createIdentifier(getSourceTextOfNodeFromSourceFile(sourceFile, namespaceDeclaration.name));
+            return isGeneratedIdentifier(name) ? name : createIdentifier(getSourceTextOfNodeFromSourceFile(sourceFile, name) || idText(name));
         }
         if (node.kind === SyntaxKind.ImportDeclaration && (<ImportDeclaration>node).importClause) {
             return getGeneratedNameForNode(node);

src/harness/unittests/transform.ts

@@ -192,6 +192,38 @@ namespace ts {
                 };
             }
         });
+
+        // https://github.com/Microsoft/TypeScript/issues/19618
+        testBaseline("transformAddImportStar", () => {
+            return ts.transpileModule("", {
+                transformers: {
+                    before: [transformAddImportStar],
+                },
+                compilerOptions: {
+                    target: ts.ScriptTarget.ES5,
+                    module: ts.ModuleKind.System,
+                    newLine: NewLineKind.CarriageReturnLineFeed,
+                }
+            }).outputText;
+
+            function transformAddImportStar(_context: ts.TransformationContext) {
+                return (sourceFile: ts.SourceFile): ts.SourceFile => {
+                    return visitNode(sourceFile);
+                };
+                function visitNode(sf: ts.SourceFile) {
+                    // produce `import * as i0 from './comp';
+                    const importStar = ts.createImportDeclaration(
+                        /*decorators*/ undefined,
+                        /*modifiers*/ undefined,
+                        /*importClause*/ ts.createImportClause(
+                            /*name*/ undefined,
+                            ts.createNamespaceImport(ts.createIdentifier("i0"))
+                        ),
+                        /*moduleSpecifier*/ ts.createLiteral("./comp1"));
+                    return ts.updateSourceFileNode(sf, [importStar]);
+                }
+            }
+        });
     });
 }
 

tests/baselines/reference/transformApi/transformsCorrectly.transformAddImportStar.js

@@ -0,0 +1,13 @@
+System.register(["./comp1"], function (exports_1, context_1) {
+    var __moduleName = context_1 && context_1.id;
+    var i0;
+    return {
+        setters: [
+            function (i0_1) {
+                i0 = i0_1;
+            }
+        ],
+        execute: function () {
+        }
+    };
+});