dedent method

@useResult String dedent()

Removes the common leading whitespace from every line.

The amount removed is the minimum of leading whitespace lengths (excluding fully blank lines). Line breaks are normalized to \n. Returns a new string with common indent removed.

Example:

'  a\n  b'.dedent();   // 'a\nb'
'  a\n    b'.dedent(); // 'a\n  b'

Implementation

@useResult
String dedent() {
  if (isEmpty) return this;
  final List<String> lines = split('\n');
  // Compute the smallest leading-whitespace width across non-blank lines.
  // Blank lines are skipped because their lead is 0 and would otherwise force
  // the common indent to 0, defeating the dedent.
  int? minLead;
  for (final String line in lines) {
    if (!line.trim().isEmpty) {
      final int lead = line.length - line.trimLeft().length;
      if (minLead == null || lead < minLead) minLead = lead;
    }
  }
  if (minLead == null || minLead == 0) {
    return this;
  }
  final lead = minLead;
  // Strip exactly `lead` chars from each line; shorter lines (blanks/whitespace
  // narrower than the common indent) are left as-is to avoid an index overrun.
  return lines
      .map((String line) => line.length >= lead ? line.replaceRange(0, lead, '') : line)
      .join('\n');
}