[Dart] Add missing output @JsonKey output for @freezed option

[kvnxiao]

Dart language enhancements:

• Resolves missing @JsonKey() for --use-freezed option https://github.com/quicktype/quicktype/issues/2162 https://github.com/quicktype/quicktype/issues/2339
• Consructors generated with --use-json-annotation or --use-freezed will respect the required keyword even if the type is considered nullable (we forgot to check if the prop was not optional!).
  • !prop.isOptional checks if the var has been explicitly defined as non-nullable
• Fixes --use-freezed option always assuming everything is nullable and appending ? to the end of the type -- this should now be covered by the required check, plus the ? was already factored in by the Dart prop type to begin with.
• Suppress comment tutorial on how to use the generated functions, when --coders-in-class is being used, since these top-level functions do not apply anymore
• Remove json_annotation import if --use-freezed is being used, since the freeze annotations import already provides json_annotation annotations.

Excerpts:

./script/quicktype --src-lang schema generated_freezed.json -l dart --use-json-annotation --use-freezed --coders-in-class generated_freezed.json

{
    "$id": "datamodel",
    "$schema": "https://json-schema.org/draft-07/schema#",
    "$ref": "#/definitions/DocumentType",
    "definitions": {
        "DocumentType": {
            "title": "DocumentType",
            "type": "object",
            "required": ["time_created"],
            "properties": {
                "time_created": {
                    "type": ["string", "null"],
                    "format": "date-time"
                }
            }
        }
    }
}

import 'package:freezed_annotation/freezed_annotation.dart';
import 'dart:convert';

part 'document_type.freezed.dart';
part 'document_type.g.dart';

@freezed
class DocumentType with _$DocumentType {
    const factory DocumentType({
        @JsonKey(name: "time_created")
        required DateTime? timeCreated,
    }) = _DocumentType;

    factory DocumentType.fromJson(Map<String, dynamic> json) => _$DocumentTypeFromJson(json);
}

Notice that time_created is nullable, but also specified as required in the JSON Schema, and this is properly reflected in the generated code.

[kvnxiao]

Hi @dvdsgl !

May I kindly also request for this to be reviewed and for a new build to be released so that we may use these fixes in production without having to run our local fork?

Thank you!

[dvdsgl]

It should have been released immediately.

[kvnxiao]

Thanks! Let me know if there's any changes needed for this PR to be merged.

[kvnxiao]

Hi @dvdsgl , apologies for the ping again but would you have some time to review this PR for this to get merged?

Thank you!

[dvdsgl]

Thank you!