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[json_codable] the object passed to fromJson is not necessarily a Map #59580

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cedvdb opened this issue Nov 21, 2024 · 3 comments · May be fixed by #59581
Open

[json_codable] the object passed to fromJson is not necessarily a Map #59580

cedvdb opened this issue Nov 21, 2024 · 3 comments · May be fixed by #59581
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area-pkg Used for miscellaneous pkg/ packages not associated with specific area- teams. pkg-json The json macro package type-enhancement A request for a change that isn't a bug

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@cedvdb
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cedvdb commented Nov 21, 2024 •
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Currently json_codable assumes that a Map is passed to the fromJson constructor when that constructor is defined by the user.

This is not supported:

@JsonCodable()
class A {
  final CustomStringSerialization customStringSerializationField;
}

class CustomStringSerialization {
  final String a;

  CustomStringSerialization(this.a);

  String toJson() => a;

  factory CustomStringSerialization.fromJson(String a) =>
      CustomStringSerialization(a);
}

Use cases:

  • deserializing values to object, for example a 'EUR' value could be deserialized to a currency object with its format method
  • it will be necessary for enum support
@dart-github-bot
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Summary: json_codable wrongly assumes fromJson receives a Map. The example shows a fromJson accepting a String, causing a failure.

@dart-github-bot dart-github-bot added area-pkg Used for miscellaneous pkg/ packages not associated with specific area- teams. triage-automation See https://github.com/dart-lang/ecosystem/tree/main/pkgs/sdk_triage_bot. type-bug Incorrect behavior (everything from a crash to more subtle misbehavior) labels Nov 21, 2024
@lrhn lrhn added type-enhancement A request for a change that isn't a bug pkg-json The json macro package and removed type-bug Incorrect behavior (everything from a crash to more subtle misbehavior) triage-automation See https://github.com/dart-lang/ecosystem/tree/main/pkgs/sdk_triage_bot. labels Nov 21, 2024
@cedvdb cedvdb linked a pull request Nov 21, 2024 that will close this issue
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@jakemac53
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cc @dart-lang/core-package-admins curious for your thoughts on the design here. See the corresponding PR as well.

I am currently leaning in the favorable direction, I don't see any real downside to the approach.

@natebosch
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The design looks sensible to me. I do think that serializing to objects other than Maps is a useful feature, and it doesn't look like it makes usage any more complex.

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area-pkg Used for miscellaneous pkg/ packages not associated with specific area- teams. pkg-json The json macro package type-enhancement A request for a change that isn't a bug
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Json codable no type assumption in custom fromJson cedvdb/sdk
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@jakemac53 @lrhn @natebosch @cedvdb @dart-github-bot