Fix nil pointer dereference in completion at property start after JSDoc

internal/fourslash/tests/completionJSDocBeforeProperty_test.go

@@ -0,0 +1,49 @@
+package fourslash_test
+
+import (
+	"testing"
+
+	"github.com/microsoft/typescript-go/internal/fourslash"
+	"github.com/microsoft/typescript-go/internal/testutil"
+)
+
+// Test for: Crash completing beginning of property name when preceded by JSDoc
+// This test verifies that requesting completions at the beginning of a property name
+// preceded by JSDoc does not cause a crash. The crash was caused by a nil pointer
+// dereference when contextToken was nil.
+func TestCompletionJSDocBeforePropertyNoCrash(t *testing.T) {
+	t.Parallel()
+	defer testutil.RecoverAndFail(t, "Panic on fourslash test")
+	const content = `export class SomeInterface {
+    /** ruh-roh! */
+    /*a*/property: string;
+}
+
+export class SomeClass {
+    /** ruh-roh! */
+    /*b*/property = "value";
+}`
+	f, done := fourslash.NewFourslash(t, nil /*capabilities*/, content)
+	defer done()
+	// The primary goal of this test is to ensure no panic occurs when requesting completions.
+	// The testutil.RecoverAndFail defer will catch any panic and fail the test.
+	// We verify completions can be requested successfully without checking specific completion items.
+	f.VerifyCompletions(t, "a", &fourslash.CompletionsExpectedList{
+		ItemDefaults: &fourslash.CompletionsExpectedItemDefaults{
+			CommitCharacters: &[]string{".", ",", ";"},
+			EditRange:        fourslash.Ignored{},
+		},
+		Items: &fourslash.CompletionsExpectedItems{
+			Includes: []fourslash.CompletionsExpectedItem{},
+		},
+	})
+	f.VerifyCompletions(t, "b", &fourslash.CompletionsExpectedList{
+		ItemDefaults: &fourslash.CompletionsExpectedItemDefaults{
+			CommitCharacters: &[]string{".", ",", ";"},
+			EditRange:        fourslash.Ignored{},
+		},
+		Items: &fourslash.CompletionsExpectedItems{
+			Includes: []fourslash.CompletionsExpectedItem{},
+		},
+	})
+}

internal/ls/completions.go

@@ -2753,7 +2753,7 @@ func getSourceFromOrigin(origin *symbolOriginInfo) string {
 func getRelevantTokens(position int, file *ast.SourceFile) (contextToken *ast.Node, previousToken *ast.Node) {
 	previousToken = astnav.FindPrecedingToken(file, position)
 	if previousToken != nil && position <= previousToken.End() && (ast.IsMemberName(previousToken) || ast.IsKeywordKind(previousToken.Kind)) {
-		contextToken := astnav.FindPrecedingToken(file, previousToken.Pos())
+		contextToken = astnav.FindPrecedingToken(file, previousToken.Pos())
 		return contextToken, previousToken
 	}
 	return previousToken, previousToken
@@ -4163,7 +4163,7 @@ func tryGetObjectTypeDeclarationCompletionContainer(
 			return nil
 		}
 		// class c extends React.Component { a: () => 1\n compon| }
-		if isFromObjectTypeDeclaration(location) {
+		if contextToken != nil && isFromObjectTypeDeclaration(location) {
 			return ast.FindAncestor(location, ast.IsObjectTypeDeclaration)
 		}
 	}