From 3ecb60146b5d91db14cf1467f4a9d9b0d25e9ce5 Mon Sep 17 00:00:00 2001
From: Vladimir Matveev <vladima@microsoft.com>
Date: Thu, 10 Nov 2016 11:57:37 -0800
Subject: [PATCH] synthesize complete import declaration for tslib (#12151)

---
 src/compiler/program.ts                        |  9 +++++++--
 src/harness/unittests/tsserverProjectSystem.ts | 17 +++++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 5cd957708f5..eb7054a9f06 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -1143,9 +1143,14 @@ namespace ts {
             if (options.importHelpers
                 && (options.isolatedModules || isExternalModuleFile)
                 && !file.isDeclarationFile) {
-                const externalHelpersModuleReference = <StringLiteral>createNode(SyntaxKind.StringLiteral);
+                // synthesize 'import "tslib"' declaration
+                const externalHelpersModuleReference = <StringLiteral>createSynthesizedNode(SyntaxKind.StringLiteral);
                 externalHelpersModuleReference.text = externalHelpersModuleNameText;
-                externalHelpersModuleReference.parent = file;
+                const importDecl = createSynthesizedNode(SyntaxKind.ImportDeclaration);
+
+                importDecl.parent = file;
+                externalHelpersModuleReference.parent = importDecl;
+
                 imports = [externalHelpersModuleReference];
             }
 
diff --git a/src/harness/unittests/tsserverProjectSystem.ts b/src/harness/unittests/tsserverProjectSystem.ts
index 17b1dd3e585..7986137ca43 100644
--- a/src/harness/unittests/tsserverProjectSystem.ts
+++ b/src/harness/unittests/tsserverProjectSystem.ts
@@ -2576,4 +2576,21 @@ namespace ts.projectSystem {
             assert.isTrue(diags.length === 0);
         });
     });
+
+    describe("import helpers", () => {
+        it("should not crash in tsserver", () => {
+            const f1 = {
+                path: "/a/app.ts",
+                content: "export async function foo() { return 100; }"
+            };
+            const tslib = {
+                path: "/a/node_modules/tslib/index.d.ts",
+                content: ""
+            };
+            const host = createServerHost([f1, tslib]);
+            const service = createProjectService(host);
+            service.openExternalProject({ projectFileName: "p", rootFiles: [toExternalFile(f1.path)], options: { importHelpers: true } });
+            service.checkNumberOfProjects({ externalProjects: 1 });
+        });
+    });
 }
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