setTransform method

void setTransform(CoercionKind kind, IValidator transformer(IValidator child), { bool dropPre = true, })

Sets a type coercion transformer with optional pre-validator preservation.

Composition Rules:

• First coercion: Sets the coercion and optionally drops pre-validators
• Subsequent coercions: If either is custom, composes them; otherwise replaces

Implementation

void setTransform(
  CoercionKind kind,
  IValidator Function(IValidator child) transformer, {
  bool dropPre = true,
}) {
  if (_coercionKind == null) {
    // First pivot: drop pre validators (they targeted old domain)
    _coercionKind = kind;
    _coercion = transformer;
    _preservePreValidators = !dropPre;
    if (dropPre) _preValidators = null;
    return;
  }
  // Subsequent pivot: compose if either current or previous is custom; replace only if both are built-in
  if (kind == CoercionKind.custom || _coercionKind == CoercionKind.custom) {
    final previous = _coercion!;
    _coercion = (child) => previous(transformer(child));
  } else {
    _coercion = transformer;
  }
  _coercionKind = kind;
  _postValidators = null;
}