cleanJsonResponse static method

@useResult String? cleanJsonResponse(String? value)

Returns a cleaned version of the JSON response value by stripping outer double-quotes and unescaping any inner escaped quotes (\"), or null if the result is empty.

Correctly handles strings that contain escaped inner quotes, e.g.: '"hello \"world\""' → 'hello "world"'. Audited: 2026-06-12 11:26 EDT

Implementation

@useResult
static String? cleanJsonResponse(String? value) {
  if (value == null || value.isEmpty) return null;

  final String trimmed = value.trim();
  if (trimmed.isEmpty) return null;

  // Detect outer quotes BEFORE unescaping inner ones.
  if (trimmed.startsWith('"') && trimmed.endsWith('"') && trimmed.length >= 2) {
    // Code-unit substring, not the grapheme-indexed substringSafe: the quote
    // detection and `trimmed.length` are code-unit measures. With substringSafe
    // a quoted value containing an astral grapheme (e.g. "🎉") clamped the end
    // index to the grapheme count and left the closing quote in place.
    final String inner = trimmed.substring(1, trimmed.length - 1);

    return inner.replaceAll(r'\"', '"').nullIfEmpty();
  }

  // No outer quotes — just unescape any escaped quotes present.
  return trimmed.replaceAll(r'\"', '"').nullIfEmpty();
}