[TrimmableTypeMap] Extract TrimmableTypeMapGenerator from MSBuild task by simonrozsival · Pull Request #11034 · dotnet/android

simonrozsival · 2026-03-27T09:31:54Z

Summary

Extract the core generation pipeline (scan → typemaps → JCW → acw-map) from the GenerateTrimmableTypeMap MSBuild task into a standalone TrimmableTypeMapGenerator class. The generator is IO-free — it accepts PEReader instances and returns in-memory content. The MSBuild task owns all filesystem IO.

Motivation

The generator logic was tightly coupled to MSBuild types (TaskLoggingHelper, ITaskItem) and performed filesystem IO directly (creating directories, checking timestamps, writing files). This made it hard to test without full MSBuild ceremony and temp directories. Extracting it with an IO-free API enables fast, focused unit tests using xUnit + TestFixtures.dll that assert on in-memory content.

Changes

New files

TrimmableTypeMapGenerator.cs — orchestrates scan → typemaps → JCW pipeline as a pure transformation: (name, PEReader)[] in → (GeneratedAssembly, GeneratedJavaSource)[] out. No filesystem IO.
TrimmableTypeMapTypes.cs — TrimmableTypeMapResult, GeneratedAssembly(Name, MemoryStream), GeneratedJavaSource(RelativePath, Content) records
NullableExtensions.cs — NRT-annotated IsNullOrEmpty/IsNullOrWhiteSpace for netstandard2.0
TrimmableTypeMapGeneratorTests.cs — 6 xUnit tests covering the generator directly (empty input, no-peers output, null validation, PE validity, Java source structure). Tests are IO-free.

Modified files

GenerateTrimmableTypeMap.cs — rewritten as IO adapter: creates PEReader instances from files, calls the generator, writes all outputs to disk using Files.CopyIfStreamChanged. Owns directory creation, assembly writing, Java source writing, acw-map generation, and MemoryStream disposal in a finally block.
GenerateTrimmableTypeMapTests.cs — 5 task-level NUnit tests: empty list, invalid TFV, valid TFV parsing (v11.0/v10.0/11.0), Mono.Android integration, incremental up-to-date check
AssemblyIndex.cs — added Create(PEReader, string) overload, removed FilePath property, no longer owns PEReader disposal
JavaPeerScanner.cs — added Scan((string, PEReader)[]) overload with shared ScanCore()
JcwJavaSourceGenerator.cs — added GenerateContent() returning (relativePath, content) pairs without filesystem writes, made Generate(type, TextWriter) public
PEAssemblyBuilder, RootTypeMapAssemblyGenerator, TypeMapAssemblyEmitter, TypeMapAssemblyGenerator — removed file-path writing overloads, stream-based output only

Design decisions

Action<string> instead of TaskLoggingHelper — keeps TrimmableTypeMap project free of Microsoft.Build packages
Generator accepts PEReader pairs (not file paths or raw streams) — PEReader already owns PE parsing; MSBuild task creates them from files, tests from in-memory bytes
All MemoryStream outputs are disposed in a finally block in the MSBuild task
Files.CopyIfStreamChanged prevents unnecessary file writes (preserving downstream incrementality)
Scanner processes all assemblies — framework JCW pre-compilation is future work ([TrimmableTypeMap] Pre-generating code for Mono.Android and other SDK assemblies #10792)

Copilot

Pull request overview

This PR refactors the trimmable typemap generation pipeline by extracting orchestration logic from the GenerateTrimmableTypeMap MSBuild task into a standalone TrimmableTypeMapGenerator class, aiming to make the logic more testable and the task a thin adapter.

Changes:

Introduces TrimmableTypeMapGenerator + TrimmableTypeMapResult to host the scan → typemap → JCW → acw-map orchestration outside the MSBuild task.
Updates GenerateTrimmableTypeMap to adapt MSBuild inputs/outputs to the new generator and adjusts tests accordingly (null → empty outputs, removed get_TargetType assertions).
Adds resource infrastructure and MSBuild package references to the TrimmableTypeMap project.

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/Generator/TypeMapModelBuilderTests.cs	Removes `get_TargetType` wrapper assertion.
tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/Generator/TypeMapAssemblyGeneratorTests.cs	Removes `get_TargetType` wrapper assertion.
src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Tasks/GenerateTrimmableTypeMapTests.cs	Updates expectations for empty outputs (null → empty).
src/Xamarin.Android.Build.Tasks/Tasks/GenerateTrimmableTypeMap.cs	Converts task into an adapter calling `TrimmableTypeMapGenerator`.
src/Microsoft.Android.Sdk.TrimmableTypeMap/TrimmableTypeMapTypes.cs	Adds `TrimmableTypeMapResult` record.
src/Microsoft.Android.Sdk.TrimmableTypeMap/TrimmableTypeMapGenerator.cs	Adds the extracted orchestration logic.
src/Microsoft.Android.Sdk.TrimmableTypeMap/Properties/Resources.resx	Adds XA4212/13/17 resource strings.
src/Microsoft.Android.Sdk.TrimmableTypeMap/Properties/Resources.Designer.cs	Adds strongly-typed resource accessors (auto-generated).
src/Microsoft.Android.Sdk.TrimmableTypeMap/NullableExtensions.cs	Adds NRT-annotated string null/empty helpers for netstandard2.0.
src/Microsoft.Android.Sdk.TrimmableTypeMap/Microsoft.Android.Sdk.TrimmableTypeMap.csproj	Adds MSBuild package refs and resource codegen configuration.
eng/Versions.props	Adds `MSBuildPackageReferenceVersion`.

Files not reviewed (1)

src/Microsoft.Android.Sdk.TrimmableTypeMap/Properties/Resources.Designer.cs: Language not supported

src/Microsoft.Android.Sdk.TrimmableTypeMap/TrimmableTypeMapGenerator.cs

src/Microsoft.Android.Sdk.TrimmableTypeMap/Properties/Resources.resx

src/Xamarin.Android.Build.Tasks/Tasks/GenerateTrimmableTypeMap.cs

src/Microsoft.Android.Sdk.TrimmableTypeMap/TrimmableTypeMapGenerator.cs

Extract the core generation pipeline (scan → typemaps → JCW → acw-map) from GenerateTrimmableTypeMap into a standalone TrimmableTypeMapGenerator class that takes Action<string> for logging, keeping the TrimmableTypeMap project free of Microsoft.Build.* dependencies. The MSBuild task becomes a thin adapter. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The per-assembly acw-map files are consumed by existing targets. Keep GeneratePerAssemblyAcwMaps in the task (it uses MSBuild types like MemoryStreamPool and Files) rather than moving the merged acw-map.txt logic to the generator, which is PR 4 work. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Restore GetJavaInteropAssemblyPaths (MonoAndroidHelper.IsMonoAndroidAssembly) filtering to match main's behavior — removing the filter is a build pipeline change that belongs in a later PR. - Add ArgumentNullException checks to TrimmableTypeMapGenerator.Execute(). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…d.Tests Move incremental build, parsing, and empty-input tests to TrimmableTypeMapGeneratorTests (xUnit, uses TestFixtures.dll). Keep MSBuild-specific tests (error handling, Mono.Android integration) in GenerateTrimmableTypeMapTests. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The scanner needs all assemblies — not just those with HasMonoAndroidReference. Framework JCW pre-compilation is tracked by #10792; until then we generate JCWs for everything. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

This is MSBuild input parsing, not core generator logic. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Generator accepts (name, PEReader) pairs, returns in-memory content - MSBuild task owns all filesystem IO - Tests assert on in-memory content, no temp dirs Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

All IO is now exclusively in the MSBuild task. The generator library only exposes stream/content-based APIs. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival

🤖 AI Review Summary

Verdict: ⚠️ Needs Changes

Found 4 issues (0 errors, 2 warnings, 2 suggestions).

Overall this is a well-executed refactor. The generator is now a clean pure transformation and the IO boundary is clearly in the MSBuild task. The PEReader-based API, metadata-derived assembly names, and in-memory result types are all good design choices.

⚠️ Resource management: MemoryStream instances in GeneratedAssembly are never disposed (TrimmableTypeMapGenerator.cs)
⚠️ Performance: Incremental build optimization removed — every run now regenerates all assemblies (GenerateTrimmableTypeMap.cs)
💡 Formatting: Indentation error on doc-comment line (JcwJavaSourceGenerator.cs:63)
💡 Code organization: GenerateContent missing XML doc-comment (JcwJavaSourceGenerator.cs:44)

👍 Good:

Clean IO-free generator with pure transformation semantics
Assembly name derived from PE metadata, not file stem — correct for cross-assembly resolution
Result types use record — good use of value equality
Files.CopyIfStreamChanged used consistently for incremental-safe writes

Review generated by android-reviewer from review guidelines.

src/Microsoft.Android.Sdk.TrimmableTypeMap/TrimmableTypeMapGenerator.cs

src/Xamarin.Android.Build.Tasks/Tasks/GenerateTrimmableTypeMap.cs

src/Microsoft.Android.Sdk.TrimmableTypeMap/Generator/JcwJavaSourceGenerator.cs

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival

🤖 AI Review Summary

Verdict: ⚠️ Needs Changes

Found 2 issues (0 errors, 1 warning, 1 suggestion):

⚠️ Testing: Several old task tests were removed but not replaced — incremental build tests, TFV parsing, no-peers-found (GenerateTrimmableTypeMapTests.cs)
💡 CI: Linux build is failing (build 1358253) — Mac/Windows still pending. Worth investigating before merge.

👍 Positive callouts

Clean IO separation — generator is fully in-memory, MSBuild task owns all filesystem operations
No null! anywhere
PEReader-based API is a smart design choice — avoids stream ownership issues
Files.CopyIfStreamChanged in the task prevents incremental build breakage
New unit tests exercise the generator directly with xUnit, no MSBuild ceremony

Review generated by android-reviewer from review guidelines.

tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/Generator/TrimmableTypeMapGeneratorTests.cs

- Restore Execute_SecondRun_OutputsAreUpToDate at task level (verifies Files.CopyIfStreamChanged does not rewrite unchanged outputs) - Restore Execute_ParsesTargetFrameworkVersion at task level - Add Execute_AssemblyWithNoPeers_ReturnsEmpty at generator level (uses test assembly itself which has no [Register] types) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival requested a review from jonathanpeppers as a code owner March 27, 2026 09:31

Copilot AI review requested due to automatic review settings March 27, 2026 09:31

Copilot started reviewing on behalf of simonrozsival March 27, 2026 09:32 View session

Copilot AI reviewed Mar 27, 2026

View reviewed changes

simonrozsival force-pushed the dev/simonrozsival/extract-trimmable-typemap-generator branch from ac38f79 to 90b195d Compare March 27, 2026 09:48

simonrozsival force-pushed the dev/simonrozsival/extract-trimmable-typemap-generator branch from 90b195d to 21facfc Compare March 27, 2026 10:00

simonrozsival added copilot `copilot-cli` or other AIs were used to author this trimmable-type-map labels Mar 27, 2026

simonrozsival and others added 5 commits March 27, 2026 11:07

Move ParseTargetFrameworkVersion to GenerateTrimmableTypeMap task

68f2409

This is MSBuild input parsing, not core generator logic. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Address review fixes

1183f9d

simonrozsival force-pushed the dev/simonrozsival/extract-trimmable-typemap-generator branch from 6cf2c60 to cd79c47 Compare March 30, 2026 11:16

Remove all IO from TrimmableTypeMapGenerator

ebfab2b

- Generator accepts (name, PEReader) pairs, returns in-memory content - MSBuild task owns all filesystem IO - Tests assert on in-memory content, no temp dirs Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival force-pushed the dev/simonrozsival/extract-trimmable-typemap-generator branch 2 times, most recently from 6c20cd9 to b70425f Compare March 30, 2026 12:04

Drop file-path scanner overloads, simplify null checks

7f8afd7

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival force-pushed the dev/simonrozsival/extract-trimmable-typemap-generator branch from b70425f to 7f8afd7 Compare March 30, 2026 12:59

Remove file-path writing overloads from generator library

5a931c3

All IO is now exclusively in the MSBuild task. The generator library only exposes stream/content-based APIs. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival force-pushed the dev/simonrozsival/extract-trimmable-typemap-generator branch from 24dd92f to 5a931c3 Compare March 30, 2026 13:50

simonrozsival commented Mar 30, 2026

View reviewed changes

simonrozsival force-pushed the dev/simonrozsival/extract-trimmable-typemap-generator branch from 4fcdbd1 to e3c2f79 Compare March 30, 2026 14:22

Address review: dispose MemoryStreams, add doc-comments, fix formatting

2e2461f

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

simonrozsival force-pushed the dev/simonrozsival/extract-trimmable-typemap-generator branch from e3c2f79 to 2e2461f Compare March 30, 2026 15:04

simonrozsival commented Mar 30, 2026

View reviewed changes

tests/Microsoft.Android.Sdk.TrimmableTypeMap.Tests/Generator/TrimmableTypeMapGeneratorTests.cs Show resolved Hide resolved

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

[TrimmableTypeMap] Extract TrimmableTypeMapGenerator from MSBuild task#11034

[TrimmableTypeMap] Extract TrimmableTypeMapGenerator from MSBuild task#11034
simonrozsival wants to merge 12 commits intomainfrom
dev/simonrozsival/extract-trimmable-typemap-generator

simonrozsival commented Mar 27, 2026 •

edited

Loading

Uh oh!

Copilot AI left a comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

simonrozsival left a comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

simonrozsival left a comment

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Conversation

simonrozsival commented Mar 27, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Summary

Motivation

Changes

New files

Modified files

Design decisions

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

simonrozsival left a comment

Choose a reason for hiding this comment

🤖 AI Review Summary

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

simonrozsival left a comment

Choose a reason for hiding this comment

🤖 AI Review Summary

👍 Positive callouts

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

simonrozsival commented Mar 27, 2026 •

edited

Loading