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[R8] Aapt2 rules are silently dropped from R8 input

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  • 何か問題がありますか？
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評価

難易度
4/5
見積もり時間
3〜5日
初心者へのやさしさ
48/100
issue の種類
バグ
明瞭さ
おおむね明確
活発さ
活発
技術スタック
android, csharp
領域
build-system, mobile-dev

調査の方向性

Start by tracing ProguardRuleOutput handling in src/Xamarin.Android.Build.Tasks/Tasks/Aapt2Link.cs around line 134, then inspect _UseAapt2ManifestProguardRules in src/Xamarin.Android.Build.Tasks/MSBuild/Xamarin/Android/Xamarin.Android.Aapt2.targets around lines 247-250. Reproduce or instrument the multi-project R8 build and verify that generated aapt_rules.txt is consistently added to ProguardConfiguration and passed to R8.

索引モデルが issue の本文から書いたものです。

説明

Area: App+Library Build need-attention
Android framework version

net10.0-android

Affected platform version

.NET 10.0.200

Description

Environment:

  • Android application with the multi-project solution;
  • AndroidLinkTool=r8
  • TrimMode=full

We are currently testing enabling full Android linking with tree-shaking. We noticed that sometimes builds compiled on CI are "broken" - crashing on startup with ClassNotFoundException. We ruled out environmental cause as there's no correlation between issue reproduction and build agents, all CI builds are "clean".
After analyzing the R8 outputs from broken builds (collected via --pg-conf-output extra argument) we found the root cause: broken builds (~4% of total) are all missing the section with generated Aapt2 rules (from aapt_rules.txt).

We managed to reproduce the issue with the additional binlog enabled, it shows the following picture:

  • _Aapt2ProguardRules is resolved into a relative path like obj/<Platform>/<Configuration>/net10.0-android36.0/aapt_rules.txt;
  • Aapt2Link task runs and competes successfully (JobWorked: True);
  • generated rules file is never added to the ProguardConfiguration - there's no Added Item(s): ProguardConfiguration=obj/.../aapt_rules.txt log;
  • aapt_rules.txt never passed to the R8, classes defined in manifest trimmed;

The issue might be caused by the Aapt2Link task operating on a relative path with incorrect captured WorkingDirectory:
https://github.com/dotnet/android/blob/7a170b185aa8e78fc18908834ada19b578668d39/src/Xamarin.Android.Build.Tasks/Tasks/Aapt2Link.cs#L134
Unlike other path variables, ProguardRuleOutput is never used with GetFullPath(), which may cause aapt_rules.txt being generated in the incorrect project. The Exists() guard then will skip adding this file to ProguardConfiguration not producing any errors
https://github.com/dotnet/android/blob/085b6f4e80f9812c3e9bb509c9b2a8a19de17d36/src/Xamarin.Android.Build.Tasks/MSBuild/Xamarin/Android/Xamarin.Android.Aapt2.targets#L247-L250

Steps to Reproduce

There are no 100% reproduction steps, the issue seems to reproduce randomly with environment described above.

Did you find any workaround?

It seems that the issue is only with the merged aapt_rules.txt, individual manifest rules per ABI are using full paths - and thus should always land in the root project. It should be possible to include those files into ProguardConfiguration directly:

<Target Name="_UseAapt2ManifestProguardRules"
        Condition="'$(AndroidLinkTool)' != ''"
        BeforeTargets="_CalculateProguardConfigurationFiles">
  <ItemGroup>
    <_Aapt2ManifestProguardRules Include="$(MSBuildProjectDirectory)/$(IntermediateOutputPath)android/*/aapt_rules.txt" />
    <ProguardConfiguration Include="@(_Aapt2ManifestProguardRules)" />
  </ItemGroup>
</Target>

Another option might be using, but we didn't test it yet

<YieldDuringToolExecution>false</YieldDuringToolExecution>
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