OptionalExtension does not support null.toOptional

[JamesMcIntosh]

Hi @tonio-ramirez,

Can you please revert the change made to OptionalExtension as it no longer handles null values with toOptional.

 Optional<T> get toOptional => Optional.of(this);

Should be

 Optional<T> get toOptional => Optional.ofNullable(this);

Missing test case for test/src/extension.dart

    test('null.toOptional == Optional.empty()', () {
      expect(null.toOptional, equals(Optional.empty()));
    });

Many thanks!
James

[tonio-ramirez]

null.toOptional is an error under Dart's sound null safety. Support for that construct was removed when support for null safety was introduced.

To be clear, even if the code were reverted to what you suggest, Dart would refuse to run code like null.toOptional, with the following error:

Error: Property 'toOptional' cannot be accessed on 'Null' because it is potentially null.

[JamesMcIntosh]

I see what you're saying, this is a more realistic test:

test('nullValue.toOptional == Optional.empty()', () {
  final String? nullValue = null;
  expect(nullValue.toOptional, equals(Optional.empty()));
});

[tonio-ramirez]

The problem isn't the test. It's that the construct isn't valid. You can't invoke methods/properties of a reference to a nullable type. The test you suggest would also fail to run, with the same error.

[JamesMcIntosh]

So sad! This makes the extension literally half as useful.
I had a good read of the GitHub discussion around this (dart-lang/language#392 & dart-lang/language#393) and can see why they chose it in regards to shorting and call ambiguity but this is the perfect case where it is needed.