Function computeAutoIndent

packages/core/src/widgets/codeEditor.ts:209–232

(
  lines: readonly string[],
  cursor: CursorPosition,
  tabSize: number = DEFAULT_TAB_SIZE,
)

 * @returns Indent string to prepend to new line
 */
export function computeAutoIndent(
  lines: readonly string[],
  cursor: CursorPosition,
  tabSize: number = DEFAULT_TAB_SIZE,
): string {
  const currentLine = lines[cursor.line] ?? "";

  // Match leading whitespace of current line
  const match = currentLine.match(/^(\s*)/);
  let indent = match ? (match[1] ?? "") : "";

  // Check if line ends with opening brace/bracket
  const trimmedBeforeCursor = currentLine.slice(0, cursor.column).trimEnd();
  if (
    trimmedBeforeCursor.endsWith("{") ||
    trimmedBeforeCursor.endsWith("[") ||
    trimmedBeforeCursor.endsWith("(") ||
    trimmedBeforeCursor.endsWith(":")
  ) {
    indent += " ".repeat(tabSize);
  }

  return indent;
}

/**
 * Indent lines in a range.