From f356cd6c8956ed274b2010b3003d237e0762816b Mon Sep 17 00:00:00 2001
From: Benjamin Lichtman <uniqueiniquity@users.noreply.github.com>
Date: Mon, 1 Oct 2018 17:43:17 -0700
Subject: [PATCH] Insert async keyword as last modifier (#27491)

---
 src/services/codefixes/convertToAsyncFunction.ts     |  2 +-
 src/services/textChanges.ts                          | 10 ++++++++++
 src/testRunner/unittests/convertToAsyncFunction.ts   |  5 +++++
 .../convertToAsyncFunction_exportModifier.js         | 12 ++++++++++++
 .../convertToAsyncFunction_exportModifier.ts         | 12 ++++++++++++
 5 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_exportModifier.js
 create mode 100644 tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_exportModifier.ts

diff --git a/src/services/codefixes/convertToAsyncFunction.ts b/src/services/codefixes/convertToAsyncFunction.ts
index fbaf0178d2..c02609e890 100644
--- a/src/services/codefixes/convertToAsyncFunction.ts
+++ b/src/services/codefixes/convertToAsyncFunction.ts
@@ -68,7 +68,7 @@ namespace ts.codefix {
         }
 
         // add the async keyword
-        changes.insertModifierBefore(sourceFile, SyntaxKind.AsyncKeyword, functionToConvert);
+        changes.insertLastModifierBefore(sourceFile, SyntaxKind.AsyncKeyword, functionToConvert);
 
         function startTransformation(node: CallExpression, nodeToReplace: Node) {
             const newNodes = transformExpression(node, transformer, node);
diff --git a/src/services/textChanges.ts b/src/services/textChanges.ts
index 756d2799a2..3b6da401db 100644
--- a/src/services/textChanges.ts
+++ b/src/services/textChanges.ts
@@ -315,6 +315,16 @@ namespace ts.textChanges {
             this.replaceRange(sourceFile, { pos, end: pos }, createToken(modifier), { suffix: " " });
         }
 
+        public insertLastModifierBefore(sourceFile: SourceFile, modifier: SyntaxKind, before: Node): void {
+            if (!before.modifiers) {
+                this.insertModifierBefore(sourceFile, modifier, before);
+                return;
+            }
+
+            const pos = before.modifiers.end;
+            this.replaceRange(sourceFile, { pos, end: pos }, createToken(modifier), { prefix: " " });
+        }
+
         public insertCommentBeforeLine(sourceFile: SourceFile, lineNumber: number, position: number, commentText: string): void {
             const lineStartPosition = getStartPositionOfLine(lineNumber, sourceFile);
             const startPosition = getFirstNonSpaceCharacterPosition(sourceFile.text, lineStartPosition);
diff --git a/src/testRunner/unittests/convertToAsyncFunction.ts b/src/testRunner/unittests/convertToAsyncFunction.ts
index 162b357847..3431603685 100644
--- a/src/testRunner/unittests/convertToAsyncFunction.ts
+++ b/src/testRunner/unittests/convertToAsyncFunction.ts
@@ -1254,6 +1254,11 @@ function [#|main2|]() {
         .then(() => { console.log("."); return delay(500); })
         .then(() => { console.log("."); return delay(500); })
 }
+`);
+_testConvertToAsyncFunction("convertToAsyncFunction_exportModifier", `
+export function [#|foo|]() {
+    return fetch('https://typescriptlang.org').then(s => console.log(s));
+}
 `);
     });
 
diff --git a/tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_exportModifier.js b/tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_exportModifier.js
new file mode 100644
index 0000000000..5ae3876f9e
--- /dev/null
+++ b/tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_exportModifier.js
@@ -0,0 +1,12 @@
+// ==ORIGINAL==
+
+export function /*[#|*/foo/*|]*/() {
+    return fetch('https://typescriptlang.org').then(s => console.log(s));
+}
+
+// ==ASYNC FUNCTION::Convert to async function==
+
+export async function foo() {
+    const s = await fetch('https://typescriptlang.org');
+    return console.log(s);
+}
diff --git a/tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_exportModifier.ts b/tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_exportModifier.ts
new file mode 100644
index 0000000000..5ae3876f9e
--- /dev/null
+++ b/tests/baselines/reference/convertToAsyncFunction/convertToAsyncFunction_exportModifier.ts
@@ -0,0 +1,12 @@
+// ==ORIGINAL==
+
+export function /*[#|*/foo/*|]*/() {
+    return fetch('https://typescriptlang.org').then(s => console.log(s));
+}
+
+// ==ASYNC FUNCTION::Convert to async function==
+
+export async function foo() {
+    const s = await fetch('https://typescriptlang.org');
+    return console.log(s);
+}