Add a testPostProcessingBuilder helper to build_test

[Fox32]

While testing builders I noticed that testBuilder only work for normal builders, but not for PostProcessBuilder. Having a testPostProcessingBuilder would be a nice addition. We have something like this in our code right now:

Future testPostProcessingBuilder(PostProcessBuilder builder,
    Map<String, /*String|List<int>*/ dynamic> sourceAssets,
    {Set<String> generateFor,
    bool Function(String assetId) isInput,
    String rootPackage,
    MultiPackageAssetReader reader,
    RecordingAssetWriter writer,
    Map<
            String,
            /*String|List<int>|Matcher<String|List<int>>*/
            dynamic>
        outputs,
    void Function(LogRecord log) onLog}) async {
  writer ??= InMemoryAssetWriter();
  final inMemoryReader = InMemoryAssetReader(rootPackage: rootPackage);
  if (reader != null) {
    reader = MultiAssetReader([inMemoryReader, reader]);
  } else {
    reader = inMemoryReader;
  }

  var inputIds = <AssetId>[];
  sourceAssets.forEach((serializedId, contents) {
    var id = makeAssetId(serializedId);
    if (contents is String) {
      inMemoryReader.cacheStringAsset(id, contents);
    } else if (contents is List<int>) {
      inMemoryReader.cacheBytesAsset(id, contents);
    }
    inputIds.add(id);
  });

  var allPackages = inMemoryReader.assets.keys.map((a) => a.package).toSet();
  for (var pkg in allPackages) {
    for (var dir in const ['lib', 'web', 'test']) {
      var asset = AssetId(pkg, '$dir/\$$dir\$');
      inputIds.add(asset);
    }
  }

  isInput ??= generateFor?.contains ?? (_) => true;
  inputIds = inputIds.where((id) => isInput('$id')).toList();

  var writerSpy = AssetWriterSpy(writer);
  var logger = Logger('testPostProcessingBuilder');
  var logSubscription = logger.onRecord.listen(onLog);

  var actualOutputs = {for (var i in inputIds) i.path: i};

  for (var inputId in inputIds) {
    await runPostProcessBuilder(builder, inputId, reader, writerSpy, logger,
        addAsset: (a) => actualOutputs[a.path] = a,
        deleteAsset: (a) => actualOutputs.remove(a.path));
  }

  await logSubscription.cancel();

  writerSpy.assetsWritten.forEach((a) => actualOutputs[a.path] = a);

  checkOutputs(outputs, actualOutputs.values, writer);
}

Which can be used like:

      await testPostProcessingBuilder(
          builder,
          {
            'builders|test/delete.txt': 'delete.txt',
            'builders|test/keep.txt': 'keep.txt',
            'builders|delete/test.json': 'delete.json',
          },
          outputs: {'builders|test/keep.txt': isNull},
          onLog: print);

Do you think this is worth a PR? How do you test post processing builders, did I miss something?

[jakemac53]

@Fox32 this seems reasonable to me - I think we just rely on integration testing for our post processing builders (we have very few and they do very little).

But some unit testing helpers would definitely be good!

[Fox32]

I will prepare a PR 🙂

[BenVercammen]

I will prepare a PR 🙂

Did you ever manage to finish your PR?

[Fox32]

Actually not 😆 I was working on it and noticed that is a bit more complex than I expected. On the other hand I noticed that I also might lack understanding of the internals to really implement a test harness that works as the real code. The code I posted above is wrong on so many levels 😆