truncateBody function

Object? truncateBody(Object? data, int maxLength)

Truncates data's string form to maxLength characters, appending a marker with the original length, so a single large body can't dominate the in-memory capture buffers.

For non-string data (typically a JSON-decoded Map/List), that string form is prettyFormatBody's indented rendering, not Object.toString — a truncated Map/List can never be valid JSON again (the cut necessarily leaves it unbalanced), so once truncated it can never be pretty-printed again either; deciding the cut point against the plain toString() (Dart's {key: value} syntax, no indentation) would have permanently frozen a large body into that single unreadable line. Pretty-printing first means the visible, truncated prefix is still properly indented, multi-line JSON, right up to the cutoff.

Raw bytes and FormData are summarized unconditionally, before the length check — prettyFormatBody's summary for either is already short regardless of the underlying payload's actual size (a multi-megabyte download summarizes just as compactly as a tiny one), so measuring that against maxLength would never trip, and the raw bytes (or a live multipart stream) would sit in the in-memory capture buffer at full size indefinitely — exactly what this function exists to prevent.

Implementation

Object? truncateBody(Object? data, int maxLength) {
  if (data == null) return null;
  if (data is Uint8List || data is FormData) return prettyFormatBody(data);
  final asString = data is String ? data : prettyFormatBody(data);
  if (asString.length <= maxLength) return data;
  return '${asString.substring(0, maxLength)}… [truncated, ${asString.length} chars total]';
}