Allow outputting to any subdirectory with `$lib$` and `$bin$` targets

[Rexios80]

For the hive_ce_generator, I need to be able to consume the entire lib folder and output a file next to a user-created file that could be anywhere in the project. Right now I believe this is impossible as you can only output a file in the root of lib or bin.

For now I am using dart:io directly, which will become a problem if #4094 ever goes through.

[rrousselGit]

Have you tried using multiple buildextensions at once?

get buildExtensions => {
    // Get access to the whole package as asset
	"$package$": [],
   // Enable output next to a specific Dart file
    "*.dart": '.myextension.dart',
}

I'm not sure if it'd work, but worth a try I think

[Rexios80]

This does not seem to work

[davidmorgan]

Hmmmmmm.

How do you identify the user-created file, does it have a particular name, particular content?

[Rexios80]

The name is user-decided, but it always contains a GenerateAdapters annotation

[davidmorgan]

Then I think the right answer is just a normal .dart generator that simply decides to do nothing for most files :)

This is somewhat inefficient, but no more so than any other annotation-based generator.

With the new triggers feature it will get much more efficient :) #4084

[davidmorgan]

One question, what does your dart:io implementation currently do?

[Rexios80]

I'm distilling the entire project into one generated file. This newly generated file goes next to the user file containing one specific annotation, but the data in the generated file is based on other annotations as well.

[Rexios80]

One question, what does your dart:io implementation currently do?

This extension allows outputting a file anywhere without restrictions

/// Convenience extension for [BuildStep]
extension BuildStepExtension on BuildStep {
  /// Create an [AssetId] for the given [path] relative to the input package
  AssetId asset(String path) => AssetId(inputId.package, path);

  /// Write [content] to asset [id] ignoring output restrictions
  ///
  /// This exists to bypass the following restrictions:
  /// - `$lib$` inputs can only have fixed output locations
  /// - Any files output through `buildStep.writeAsString` will be deleted
  ///   before the build starts
  void forceWriteAsString(AssetId id, String content) {
    File(path.joinAll(id.pathSegments))
      ..createSync(recursive: true)
      ..writeAsStringSync(content);
  }
}

The forceWriteAsString function is used in these places:

• https://github.com/IO-Design-Team/hive_ce/blob/e515c59958bee586a0ce483c5cbe4c24eb333d6f/hive_generator/lib/src/builder/registrar_builder.dart#L116
• https://github.com/IO-Design-Team/hive_ce/blob/e515c59958bee586a0ce483c5cbe4c24eb333d6f/hive_generator/lib/src/generator/adapters_generator.dart#L96
• https://github.com/IO-Design-Team/hive_ce/blob/e515c59958bee586a0ce483c5cbe4c24eb333d6f/hive_generator/lib/src/builder/schema_migrator_builder.dart#L162
• https://github.com/IO-Design-Team/hive_ce/blob/e515c59958bee586a0ce483c5cbe4c24eb333d6f/hive_generator/lib/src/builder/schema_migrator_builder.dart#L175

This code reads the user-created ignore_for_file config since the generator using this isn't actually a source_gen|combining_builder

final ignores = <String>[];
final buildConfigFile = File('build.yaml');
if (buildConfigFile.existsSync()) {
  final buildConfigContent = buildConfigFile.readAsStringSync();
  final buildConfig = loadYaml(buildConfigContent);
  final configIgnores = buildConfig?['targets']?[r'$default']?['builders']
              ?['source_gen|combining_builder']?['options']
          ?['ignore_for_file'] as YamlList? ??
      [];
  ignores.addAll(configIgnores.cast<String>());
}

Is there some built in method of reading the config of other builders?

[davidmorgan]

Thanks.

I'm distilling the entire project into one generated file. This newly generated file goes next to the user file containing one specific annotation, but the data in the generated file is based on other annotations as well.

Right, I think the way to do that is by running on all .dart files but only writing something if the annotation is there.

But: now I realize this is also the case where you want to update an input. Then, I think actually you only need the "allow generators to update inputs" feature, since there will (I guess) be no restrictions on which file(s) the generator can suggest changes to.

Is there some built in method of reading the config of other builders?

No, but a pending request :) I think that's the same as #3988

[Rexios80]

Right, I think the way to do that is by running on all .dart files but only writing something if the annotation is there.

Does that allow me to read many annotations from many files and combine that data into one single generated file?

[davidmorgan]

Right, I think the way to do that is by running on all .dart files but only writing something if the annotation is there.

Does that allow me to read many annotations from many files and combine that data into one single generated file?

Yes, a build step can read from any source in the root package and its transitive dependencies.

[Rexios80]

Hmmmm. I could have sworn you could only read the file in your current scope. As in if you target an annotation you can only read the file containing it.

That sounds like it could work, except there is an edge case in which the annotation does not exist and then the generated file goes in the root of the lib folder.

[Rexios80]

Maybe I could split it into two separate generators