Disable "when" generation by default

[rrousselGit]

Related to #924

In a "Freezed 3.0" version, we could disable "when" by default (and enable its generation through build.yaml).

[Reprevise]

In general, I am in favor of this however I am also a big fan of this pattern here which AFAIK there's no equivalent behavior in Dart's pattern matching syntax:

return Scaffold(
  appBar: /* ... */,
  body: state.when(
    // ...
  ),
);

This pattern is commonly used in riverpod with AsyncValue which I know isn't really related to freezed but it is the same exact syntax. Are you going to be pushing for that to change too?

[rrousselGit]

AFAIK there's no equivalent behavior in Dart's pattern matching syntax:

return Scaffold(
  appBar: /* ... */,
  body: state.when(
    // ...
  ),
);

You can dk:

body: switch (state) {
...
}

This pattern is commonly used in riverpod with AsyncValue which I know isn't really related to freezed but it is the same exact syntax. Are you going to be pushing for that to change too?

Yes, the same logic will be applied.

[Reprevise]

Alright, though I do have a specific case where I need a block body so a switch expression won't work there, but I'll just force-enable when generation for that class since IMO it looks nicer than making 4 methods for each case just to make an expression work.

I have already disabled when/map generation globally across my project in preparation for the next update and I only have to enable when generation manually on one class so I think that's pretty good overall.

[timnew]

@rrousselGit I feel the pattern matching in dart does covering all the scenarios that legacy map and when provided.

Here is an example:

  VerifiedTextState markAsVisited(String file, FilePosition? position) =>
      switch (this) {
        PassedText() => (this as PassedText).copyWith(isVisited: true),
        IllegalText() =>
          (this as IllegalText).copyWith(file: file, position: position),
        _ => throw Exception("Unknown text state: $this"),
      };

  VerifiedTextState markAsVisitedLegacy(String file, FilePosition? position) =>
      map(
        passed: (state) => state.copyWith(isVisited: true),
        illegal: (state) => state.copyWith(file: file, position: position),
      );

So there is 2 major issues here when destructing isn't the purpose:

1. Pattern matching seems doesn't include a type assertion, so extra type case is needed, which is kind of partially defeated the reason to have a pattern matching.
2. Freezed doesn't include sealed keyword to the sub types, so the exhaustiveness check fails if extra _ is missing.

Any suggestion to these issues?

[rrousselGit]

Freezed doesn't include sealed keyword to the sub types, so the exhaustiveness check fails if extra _ is missing.

It's your class that needs to be sealed, not the generated code

@freezed
sealed class Foo {....}

Pattern matching seems doesn't include a type assertion, so extra type case is needed, which is kind of partially defeated the reason to have a pattern matching.

Dart doesn't support upcasting this. So use a variable:

switch (this) {
  final PassedText state => state.copyWith(isVisited: true),
}

[timnew]

Thanks for the quick responding!

Now I can happily get rid of @Freezed(map: FreezedMapOptions.all)