[simonrozsival]

Context: #13460

<GetAndroidDefineConstants/> turns $(MonoAndroidVersion) into a __XAMARIN_ANDROID_*__ define by replacing every non-alphanumeric character via Regex.Replace (ProductVersion, "[^A-Za-z0-9]", "_"). Xamarin.Android.Build.Tasks targets netstandard2.0, so that pattern is parsed and interpreted at runtime on every build.

Following #13460, move the task into Microsoft.Android.Build.Tasks (net12.0) and the Microsoft.Android.Tasks namespace, so the fixed pattern can use a source-generated [GeneratedRegex] partial property. The pattern text is unchanged and uses no RegexOptions, so matching semantics are identical (no culture-sensitive IgnoreCase concerns). The task keeps its existing MultithreadedAndroidTask base.

The task is registered through the same Full/Core <UsingTask/> pair as the other Microsoft.Android.Build.Tasks tasks; the unqualified <GetAndroidDefineConstants/> invocation in Xamarin.Android.Common.targets is unchanged. The old Xamarin.Android.Tasks.GetAndroidDefineConstants type is removed.

MonoAndroidHelper.TryParseApiLevel() moves from MonoAndroidHelper.cs to MonoAndroidHelper.Basic.cs, which is already compile-linked into Microsoft.Android.Build.Tasks. As that file is nullable-enabled, the method is now annotated (string? apiLevel, [NotNullWhen (true)] out Version? version); Aapt2Link uses out var to match. Behavior is unchanged.

The existing tests move to Microsoft.Android.Build.Tasks.Tests, plus a test that loads the registrations from Xamarin.Android.Common.targets and runs both <GetAndroidDefineConstants/> and <Microsoft.Android.Tasks.GetAndroidDefineConstants/> through dotnet msbuild.

Known limitation (shared with every net12.0 Microsoft.Android.Build.Tasks task): it fails with MSB4061 under .NET 11 MSBuild.

Alternative considered: MSBuild XML

Rewriting the task as a plain MSBuild target would avoid the task, its <UsingTask/> pair, and the MSB4061 limitation. A prototype using $([System.Version]::Parse()) and $([System.Text.RegularExpressions.Regex]::Replace()) produced identical @(AndroidDefineConstants) for _AndroidApiLevel values 21, 36, 36.1, 37, 37.0.1, 37.2, 38.2, and 40.3. However, MSBuild has no range loop, so 1..$(major) and the quarterly __ANDROID_{api}_{minor}__ constants needed a "tens digit × ones digit" item cross-product capped at API-99, with property round-trips to split transform output. The target took ~11 ms vs ~3 ms for the task (median of 15 fresh dotnet msbuild runs, -clp:PerformanceSummary). The C# task is kept because it is much easier to read and test.

Validation

• dotnet build src/Microsoft.Android.Build.Tasks/Tests/Microsoft.Android.Build.Tasks.Tests/Microsoft.Android.Build.Tasks.Tests.csproj (builds MABT too): succeeded, 0 errors.
• dotnet test bin/TestDebug/net12.0/Microsoft.Android.Build.Tasks.Tests.dll --filter "FullyQualifiedName~GetAndroidDefineConstantsTests": Passed 7, Failed 0.
• ./dotnet-local.sh build src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.csproj -p:BuildProjectReferences=false: succeeded, 0 errors.
• ./dotnet-local.sh build src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Xamarin.Android.Build.Tests.csproj -p:DisableApiCompatibilityCheck=True: succeeded (compile check only; ApiCompat skipped because its package was missing from the isolated NuGet cache used locally).
• Not run: a full-SDK app build through Xamarin.Android.Build.Tests. Free disk space on the shared build host was too low for make leeroy. The new dotnet msbuild test covers the Xamarin.Android.Common.targets registration.

Measurements

Fresh-process harness: load the task assembly, Execute() with AndroidApiLevel=37.1 and ProductVersion=37.0.99-ci.main+sha.9f23d997e4. Medians over 30 processes, two interleaved rounds:

	first Execute()	second Execute()
before (XABT, netstandard2.0, Regex.Replace)	7.32 / 7.17 ms	12.4 / 12.0 µs
after (MABT, net12.0, [GeneratedRegex])	5.74 / 5.77 ms	9.7 / 9.8 µs

That is about 1.5 ms (~20%) less on first use. The numbers measure the whole task, including assembly differences, not just the regex.

[Copilot]

🟢 Approval recommended

The task migration has no active review issues blocking approval.

No open issues 🎉

What changed in this PR

Moves GetAndroidDefineConstants into the modern .NET task assembly, continuing the migration in #13460 and enabling a source-generated regex without changing the matching pattern.

Changes:

• Migrates the task to Microsoft.Android.Tasks and updates its Full/Core MSBuild registrations.
• Relocates API-level parsing into the shared helper, adding nullable annotations and adjusting callers.
• Moves existing tests and adds registration tests for both short and fully qualified task names.

File	Description
src/​Xamarin.Android.Build.Tasks/​Xamarin.Android.Common.targets	Registers the migrated task using the Full/Core hosting pair.
src/​Xamarin.Android.Build.Tasks/​Utilities/​MonoAndroidHelper.cs	Removes the relocated API-level parser.
src/​Xamarin.Android.Build.Tasks/​Utilities/​MonoAndroidHelper.Basic.cs	Adds the shared parser with nullable annotations.
src/​Xamarin.Android.Build.Tasks/​Tests/​Xamarin.Android.Build.Tests/​Tasks/​GetAndroidDefineConstantsTests.cs	Removes tests from the legacy test project.
src/​Xamarin.Android.Build.Tasks/​Tasks/​Aapt2Link.cs	Uses inferred output types for the updated parser.
src/​Microsoft.Android.Build.Tasks/​Tests/​Microsoft.Android.Build.Tasks.Tests/​Tasks/​GetAndroidDefineConstantsTests.cs	Adds migrated tests and MSBuild task-name registration coverage.
src/​Microsoft.Android.Build.Tasks/​Tasks/​GetAndroidDefineConstants.cs	Migrates the task and replaces runtime regex parsing with a generated regex.

_{Review effort: Balanced}

[simonrozsival]

/review

[github-actions]

✅ Android PR Reviewer completed successfully!

Generated by Android PR Reviewer for #13477

[github-actions]

Code assessment: no blocking findings. 0 errors, 0 warnings, 1 non-blocking inline suggestion.

The generated regex preserves the original ASCII character-class replacement semantics, the API-level parser move preserves behavior while adding nullable flow annotations, and the task retains its multithreadable declaration and base class. The registrations follow the existing Full/Core pattern, and the moved tests retain the previous constant-generation coverage while adding short-name and qualified-name task resolution coverage. The reported timing measurements appropriately distinguish whole-task execution from regex-only performance.

CI: All 41 GitHub check runs report success, including the aggregate dotnet-android check for Azure build 1674337. Independent Azure build/timeline verification was blocked by CLI initialization/authentication errors, so I cannot independently confirm the Azure result or its stage details. No local tests were run in this review; the active SDK is .NET 10.0.403, while the affected task and test projects target net12.0.

Generated by Android PR Reviewer for #13477 · copilot · gpt61 · 45.9 AIC · ⌖ 4.1 AIC · ⊞ 19.4K
_{Comment /review to run again}

[github-actions]

🤖 💡 Testing — Consider adding a Windows-only variant that runs this generated project with full-framework MSBuild.exe. Both current cases invoke dotnet msbuild, so MSBuildRuntimeType is always Core; copying both registrations and asserting their count does not exercise the Full registration or the new out-of-process task-host boundary. Running the same output assertions through that host would protect the Visual Studio path when migrating this task out of the netstandard assembly.

{Rule: Test host-specific execution paths}