record static method

String record(String catalog, String key, String value, { bool expansion = false, })

The token for one read: == the value, and its own object.

Not the stored string. A catalog compiled as a const Dart map hands out canonicalised literals, so two keys sharing a value would be one object — and, worse, a hardcoded 'Cancel' in the UI would be identical to the catalog's and be attributed to a key it never came from. Measured on a real catalog: 29 values shared by 66 of 545 keys. Minting a copy makes the mechanism independent of how the catalog is stored.

String.fromCharCodes because it is one of only two expressions that actually allocate. '$value', value.substring(0) and a StringBuffer all hand back the same instance — the obvious ways to force a copy silently do nothing, and would have made this work on a JSON catalog and fail on a compiled one.

Implementation

static String record(
  String catalog,
  String key,
  String value, {
  bool expansion = false,
}) {
  if (!recording) return value;
  if (!expansion) (_read[catalog] ??= {})[key] = value;
  // An empty value has no glyphs to carry identity, and the empty string is
  // canonical besides. Recorded above, so a key that renders nothing is still
  // reportable; it just cannot be found on a screen.
  if (value.isEmpty) return value;
  // A budget pass pads what renders, never what was read: `_read` above
  // keeps the real value. Expansions pad too — the built string is the one
  // on screen, so it is the one whose room is being measured.
  var minted = switch (expandPercent) {
    var percent? =>
      value +
          expansionPadding(
            catalog,
            key,
            expansionLength(value.length, percent),
          ),
    _ => value,
  };
  var token = _tokens.putIfAbsent(
    '$catalog$key$minted',
    () => String.fromCharCodes(minted.codeUnits),
  );
  _keys[token] = TranslationKey(catalog, key);
  return token;
}