I'm trying to create custom builder for my Flutter project. I want to achieve something similar to built_value code generation.
I've started by creating build.yaml in the root folder of my project
targets:
$default:
builders:
app|db_builder:
enabled: true
builders:
db_builder:
target: ":db_builder"
import: "package:app/db/build/builder.dart"
builder_factories: ["dbBuilder"]
build_extensions: {".dart": [".db.g.part"]}
auto_apply: dependents
build_to: cache
applies_builders: ["source_gen|combining_builder"]
Then implemented dbBuilder factory at app/db/build/builder.dart
import 'package:build/build.dart';
import 'package:source_gen/source_gen.dart';
import 'db_generator.dart';
Builder dbBuilder(BuilderOptions _) =>
SharedPartBuilder([DBAccessGenerator()], 'built_value');
DBAccessGenerator is an empty class inherited from Generator
My project also contains built_value_generator.
After the above mentioned steps, when running flutter pub run build_runner build I've got the following error:
Both app:db_builder and built_value_generator:built_value may output
test/widget_test.built_value.g.part. Potential outputs must be unique across all builders.
Why this happens? I've seen the source code of built_value_generator and it declares build extensions as build_extensions: {".dart": [".built_value.g.part"]} but my declaration differs, I'm using another target extension.
The reason is inside the app/db/build/builder.dart file.
When creating SharedPartBuilder, the second argument is a partId and it is the real output extension of a generated file, not a one specified in a build.yaml file.
So, setting another name here fixes the problem.