Locale aware double input

[t-unit]

Environment

Package version: 17.0.1

Describe your question

Depending on the local/language setting of an app, users expect to input floating point number with varying decimal separators. (E.g. see https://en.wikipedia.org/wiki/Decimal_separator#Conventions_worldwide).

I found that this library does not have any support for locale aware parsing, as DoubleValueAccessor is using double.tryParse that does not take any locale into account.

1. What is the intended way to deal with different locales and floating point formats an this library?
2. Shouldn't this library already take care of this an provide proper parsing for any locals? (It already has a dependency towards intl)

We came up with a custom value accessor:

class NumberFormatDoubleValueAccessor extends ControlValueAccessor<double, String> {
  NumberFormatDoubleValueAccessor(this.format);

  final NumberFormat format;

  @override
  String modelToViewValue(double? modelValue) => format.format(modelValue);

  @override
  double? viewToModelValue(String? viewValue) =>
      (viewValue == '' || viewValue == null)
          ? null
          : format.tryParse(viewValue)?.toDouble();
}

that allows specifying a format like NumberFormatDoubleValueAccessor(NumberFormat.decimalPattern('de')).