From d4f26c840b1db76c0b25a405c8e73830a2b45cbc Mon Sep 17 00:00:00 2001
From: Oleksandr T <oleksandr.tarasiuk@outlook.com>
Date: Wed, 26 Oct 2022 23:59:44 +0300
Subject: [PATCH] fix(51245): Class with parameter decorator in arrow function
 causes "convert to default export" refactoring failure (#51256)

* fix(51245): don't rely on parent nodes in formatting rules

* check existing parent node
---
 src/services/formatting/rules.ts              |  4 ++--
 ... refactorConvertExport_namedToDefault1.ts} |  0
 .../refactorConvertExport_namedToDefault2.ts  | 23 +++++++++++++++++++
 3 files changed, 25 insertions(+), 2 deletions(-)
 rename tests/cases/fourslash/{refactorConvertExport_namedToDefault.ts => refactorConvertExport_namedToDefault1.ts} (100%)
 create mode 100644 tests/cases/fourslash/refactorConvertExport_namedToDefault2.ts

diff --git a/src/services/formatting/rules.ts b/src/services/formatting/rules.ts
index 85e67eb8cbb59..07724be25ba0e 100644
--- a/src/services/formatting/rules.ts
+++ b/src/services/formatting/rules.ts
@@ -732,10 +732,10 @@ namespace ts.formatting {
     }
 
     function nodeIsInDecoratorContext(node: Node): boolean {
-        while (isExpressionNode(node)) {
+        while (node && isExpression(node)) {
             node = node.parent;
         }
-        return node.kind === SyntaxKind.Decorator;
+        return node && node.kind === SyntaxKind.Decorator;
     }
 
     function isStartOfVariableDeclarationList(context: FormattingContext): boolean {
diff --git a/tests/cases/fourslash/refactorConvertExport_namedToDefault.ts b/tests/cases/fourslash/refactorConvertExport_namedToDefault1.ts
similarity index 100%
rename from tests/cases/fourslash/refactorConvertExport_namedToDefault.ts
rename to tests/cases/fourslash/refactorConvertExport_namedToDefault1.ts
diff --git a/tests/cases/fourslash/refactorConvertExport_namedToDefault2.ts b/tests/cases/fourslash/refactorConvertExport_namedToDefault2.ts
new file mode 100644
index 0000000000000..3692e8493a5ae
--- /dev/null
+++ b/tests/cases/fourslash/refactorConvertExport_namedToDefault2.ts
@@ -0,0 +1,23 @@
+/// <reference path='fourslash.ts' />
+
+// @Filename: /a.ts
+/////*a*/export const f = () => {
+////    return class C {
+////        constructor(@Foo() param: any) { }
+////    }
+////}/*b*/
+////function Foo(...args: any[]): any {}
+
+goTo.select("a", "b");
+edit.applyRefactor({
+    refactorName: "Convert export",
+    actionName: "Convert named export to default export",
+    actionDescription: "Convert named export to default export",
+    newContent:
+`export default () => {
+    return class C {
+        constructor(@Foo() param: any) { }
+    }
+}
+function Foo(...args: any[]): any {}`,
+});