How to run json_serializable over output of another builder?

Question

I have made a SharedPartBuilder that generates new class annotated with @JsonSerializable(). How can I configure json_serializable to run over .part file generated by my builder before all .part files are combined into one .g.dart?

Inside build.yaml, I have tried adding to my builder runs_before: ["json_serializable"] and applies_builders: ["json_serializable"] or applies_builders: ["source_gen|combining_builder", "json_serializable"] all without success.

EDIT: It seems this is not possible when using SharedPartBuilder.

No SharedPartBuilder will be able to resolve the Dart code emitted by another SharedPartBuilder. In order for emitted code to be used with the Resolver by later build steps, it must write to a .dart file directly, and should be a different file extension than .g.dart.

https://github.com/dart-lang/build/blob/master/docs/builder_author_faq.md

Answer 1

This is not possible when using SharedPartBuilder.

No SharedPartBuilder will be able to resolve the Dart code emitted by another SharedPartBuilder. In order for emitted code to be used with the Resolver by later build steps, it must write to a .dart file directly, and should be a different file extension than .g.dart.

https://github.com/dart-lang/build/blob/master/docs/builder_author_faq.md

To make it work, I changed my SharedPartBuilder to PartBuilder and set generatedExtension to end with .dart.

In build.yaml I changed from build_to: cache to build_to: source.

I can comment out applies_builders ... and keep just runs_before: ["json_serializable"] and it still works.