Bazel: Support D8

[jin]

The latest Android Plugin for Gradle v3.1.0 sets D8 as the default dexer, we should add support to use it in android_sdk.

[jin]

This isn't in buildtools yet, so we'll have to fetch it in WORKSPACE or vendor it.

[jin]

Now available in buildtools 28.0.1

[jin]

I am not working on this currently.

[madsager]

What is the status of this? Dx is no longer supported and bazel is the only one using it by default. I am getting reports from a couple of bazel users that are seeing dx fail on their code and d8 does not fail. Is there anything I can do to help move this forward?

[nkoroste]

ping - any updates on this?

[anuchandy]

Any updates on this?

[rzsombor]

The 1.2 release notes hints that D8 is supported on an experimental basis. This issue is referenced there - it's a bit odd to see no updates here.

[gyias]

Yes, the 1.2 release adds D8 support. Let me know if you see any issues.

[gyias]

Quick note on how to actually use d8 in lieu of dx or DexBuilder.

• To use the standalone d8 dexer:
  bazel build --noincremental_dexing --define=android_standalone_dexing_tool=d8_compat_dx

• To use incremental d8 dexer:
  bazel build --define=android_incremental_dexing_tool=d8_dexbuilder --nouse_workers_with_dexbuilder

You can also add the below lines to your .bazelrc and switch to d8 by simply specifying --config=d8 in your build command line.

# Flags for using the D8 dexer.
build:d8 --define=android_incremental_dexing_tool=d8_dexbuilder
build:d8 --define=android_standalone_dexing_tool=d8_compat_dx
build:d8 --nouse_workers_with_dexbuilder

Or, even make it default by adding:
build --config=d8

[nkoroste]

@gyias the .bazelrc configuration don't exactly match your explicit commands. Shouldn't it be:

build:d8 --nouse_workers_with_dexbuilder --define=android_incremental_dexing_tool=d8_dexbuilder
build:d8 --noincremental_dexing --define=android_standalone_dexing_tool=d8_compat_dx

Otherwise you will apply --nouse_workers_with_dexbuilder to d8_compat_dx which is unintentional? and not apply --nouse_workers_with_dexbuilder which is also unintentional?

---

In general, I tried the new D8 dexer and I noticed that even though it uses the correct
bazel-out/host/bin/external/bazel_tools/tools/android/d8_dexbuilder
or
bazel-out/host/bin/external/androidsdk/d8_compat_dx

But it still uses the older dexMerger:

bazel-out/host/bin/external/bazel_tools/src/tools/android/java/com/google/devtools/build/android/dexer/DexFileMerger

is that expected?

[gyias]

@gyias the .bazelrc configuration don't exactly match your explicit commands. Shouldn't it be:

build:d8 --nouse_workers_with_dexbuilder --define=android_incremental_dexing_tool=d8_dexbuilder
build:d8 --noincremental_dexing --define=android_standalone_dexing_tool=d8_compat_dx

Otherwise you will apply --nouse_workers_with_dexbuilder to d8_compat_dx which is unintentional? and not apply --nouse_workers_with_dexbuilder which is also unintentional?

No, the sample config is correct. --nouse_workers_with_dexbuilder has no effect d8_compat_dx as it's specifically the for incremental dexing mode. Basically, the sample config applies all three flags when the user specifies --config=d8, and then the user can switch between d8_compat_dx and d8_dexbuilder using --noincremental_dexing, the default being d8_dexbuilder.

In general, I tried the new D8 dexer and I noticed that even though it uses the correct
bazel-out/host/bin/external/bazel_tools/tools/android/d8_dexbuilder
or
bazel-out/host/bin/external/androidsdk/d8_compat_dx

But it still uses the older dexMerger:

bazel-out/host/bin/external/bazel_tools/src/tools/android/java/com/google/devtools/build/android/dexer/DexFileMerger

is that expected?

Yes, I'm not sure if there's an existing issue to cover it though. I'll create one if there isn't. Thanks for pointing it out.

[nkoroste]

Thanks for the quick reply!
Do you mind linking me to the new issue when you create it? I'm trying to workaround some DexFileMerger related issues:
https://github.com/bazelbuild/bazel/issues/9384
https://github.com/bazelbuild/bazel/issues/9383

and so far the only thing that works is not using incremental dexing which impacts performance.

[gyias]

Sure, I couldn't find, and so created one.

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