fix(33286): add outlining for arrow function with one parameter

Author: a-tarasyuk

src/services/outliningElementsCollector.ts

@@ -272,9 +272,7 @@ namespace ts.OutliningElementsCollector {
     }
 
     function functionSpan(node: FunctionLike, body: Block, sourceFile: SourceFile): OutliningSpan | undefined {
-        const openToken = isNodeArrayMultiLine(node.parameters, sourceFile)
-            ? findChildOfKind(node, SyntaxKind.OpenParenToken, sourceFile)
-            : findChildOfKind(body, SyntaxKind.OpenBraceToken, sourceFile);
+        const openToken = tryGetFunctionOpenToken(node, body, sourceFile);
         const closeToken = findChildOfKind(body, SyntaxKind.CloseBraceToken, sourceFile);
         return openToken && closeToken && spanBetweenTokens(openToken, closeToken, node, sourceFile, /*autoCollapse*/ node.kind !== SyntaxKind.ArrowFunction);
     }
@@ -287,4 +285,14 @@ namespace ts.OutliningElementsCollector {
     function createOutliningSpan(textSpan: TextSpan, kind: OutliningSpanKind, hintSpan: TextSpan = textSpan, autoCollapse = false, bannerText = "..."): OutliningSpan {
         return { textSpan, kind, hintSpan, bannerText, autoCollapse };
     }
+
+    function tryGetFunctionOpenToken(node: FunctionLike, body: Block, sourceFile: SourceFile): Node | undefined {
+        if (isNodeArrayMultiLine(node.parameters, sourceFile)) {
+            const openParenToken = findChildOfKind(node, SyntaxKind.OpenParenToken, sourceFile);
+            if (openParenToken) {
+                return openParenToken;
+            }
+        }
+        return findChildOfKind(body, SyntaxKind.OpenBraceToken, sourceFile);
+    }
 }

tests/cases/fourslash/getOutliningForArrowFunctionBody1.ts

@@ -0,0 +1,10 @@
+/// <reference path="fourslash.ts"/>
+
+////declare function foo(props: any);
+////foo(
+////    a =>[| {
+////
+////    }|]
+////)
+
+verify.outliningSpansInCurrentFile(test.ranges(), "code");

tests/cases/fourslash/getOutliningForArrowFunctionBody2.ts

@@ -0,0 +1,10 @@
+/// <reference path="fourslash.ts"/>
+
+////declare function foo(props: any);
+////foo(
+////    (a) =>[| {
+////
+////    }|]
+////)
+
+verify.outliningSpansInCurrentFile(test.ranges(), "code");

tests/cases/fourslash/getOutliningForArrowFunctionBody3.ts

@@ -0,0 +1,10 @@
+/// <reference path="fourslash.ts"/>
+
+////declare function foo(props: any);
+////foo(
+////    (a, b, c) =>[| {
+////
+////    }|]
+////)
+
+verify.outliningSpansInCurrentFile(test.ranges(), "code");