Fix nil pointer panic in FormatOnEnter

internal/format/format_test.go

@@ -1,6 +1,7 @@
 package format_test
 
 import (
+	"context"
 	"strings"
 	"testing"
 
@@ -58,3 +59,67 @@ func TestFormatNoTrailingNewline(t *testing.T) {
 		})
 	}
 }
+
+// Test for panic handling request textDocument/onTypeFormatting (issue #2042)
+// The panic occurs when getStartLineAndCharacterForNode is called with a nil node
+func TestFormatOnEnter_NilNodeHandling(t *testing.T) {
+	t.Parallel()
+
+	// Test various edge cases that could lead to nil nodes being passed
+	// to getStartLineAndCharacterForNode
+	testCases := []struct {
+		name     string
+		text     string
+		position int // position where enter is pressed
+	}{
+		{
+			name:     "empty file",
+			text:     "",
+			position: 0,
+		},
+		{
+			name:     "simple statement",
+			text:     "const x = 1;",
+			position: 12,
+		},
+		{
+			name:     "file with newline",
+			text:     "const x = 1;\n",
+			position: 13,
+		},
+		{
+			name:     "incomplete code",
+			text:     "if (",
+			position: 4,
+		},
+		{
+			name:     "malformed if-else",
+			text:     "if(a){}\nelse",
+			position: 12,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			sourceFile := parser.ParseSourceFile(ast.SourceFileParseOptions{
+				FileName: "/test.ts",
+				Path:     "/test.ts",
+			}, tc.text, core.ScriptKindTS)
+
+			ctx := format.WithFormatCodeSettings(context.Background(), &format.FormatCodeSettings{
+				EditorSettings: format.EditorSettings{
+					TabSize:             4,
+					IndentSize:          4,
+					NewLineCharacter:    "\n",
+					ConvertTabsToSpaces: true,
+					IndentStyle:         format.IndentStyleSmart,
+				},
+			}, "\n")
+
+			// This should not panic even with nil nodes
+			edits := format.FormatOnEnter(ctx, sourceFile, tc.position)
+			_ = edits // Just ensuring no panic
+		})
+	}
+}

internal/format/indent.go

@@ -242,6 +242,9 @@ func findFirstNonWhitespaceCharacterAndColumn(startPos int, endPos int, sourceFi
 func childStartsOnTheSameLineWithElseInIfStatement(parent *ast.Node, child *ast.Node, childStartLine int, sourceFile *ast.SourceFile) bool {
 	if parent.Kind == ast.KindIfStatement && parent.AsIfStatement().ElseStatement == child {
 		elseKeyword := astnav.FindPrecedingToken(sourceFile, child.Pos())
+		if elseKeyword == nil {
+			return false
+		}
 		debug.AssertIsDefined(elseKeyword)
 		elseKeywordStartLine, _ := getStartLineAndCharacterForNode(elseKeyword, sourceFile)
 		return elseKeywordStartLine == childStartLine
@@ -250,6 +253,9 @@ func childStartsOnTheSameLineWithElseInIfStatement(parent *ast.Node, child *ast.
 }
 
 func getStartLineAndCharacterForNode(n *ast.Node, sourceFile *ast.SourceFile) (line int, character int) {
+	if n == nil {
+		return 0, 0
+	}
 	return scanner.GetECMALineAndCharacterOfPosition(sourceFile, scanner.GetTokenPosOfNode(n, sourceFile, false))
 }
 
@@ -530,8 +536,12 @@ func childIsUnindentedBranchOfConditionalExpression(parent *ast.Node, child *ast
 			//   ? 1 : (          L1: whenTrue indented because it's on a new line
 			//     0              L2: indented two stops, one because whenTrue was indented
 			//   );                   and one because of the parentheses spanning multiple lines
-			trueStartLine, _ := getStartLineAndCharacterForNode(parent.AsConditionalExpression().WhenTrue, sourceFile)
-			trueEndLine, _ := scanner.GetECMALineAndCharacterOfPosition(sourceFile, parent.AsConditionalExpression().WhenTrue.End())
+			whenTrue := parent.AsConditionalExpression().WhenTrue
+			if whenTrue == nil {
+				return false
+			}
+			trueStartLine, _ := getStartLineAndCharacterForNode(whenTrue, sourceFile)
+			trueEndLine, _ := scanner.GetECMALineAndCharacterOfPosition(sourceFile, whenTrue.End())
 			return conditionEndLine == trueStartLine && trueEndLine == childStartLine
 		}
 	}