[Apple mobile] Stage the Helix R2R app payload outside the crossgen2 input directory

[davidnguyen-tech]

Fixes #131922

Problem

Apple mobile CoreCLR test apps are ReadyToRun-compiled on the Helix machine from assemblies in publish/. The build process then copied Crossgen2 output back into that same directory.

Helix retries reuse the work-item directory. A retry therefore fed attempt 1's already-compiled, IL-stripped assemblies back into Crossgen2. The resulting app crashed before test discovery:

Fatal error.
A method body required at runtime was stripped from the ReadyToRun image.

This is retry input corruption in the build orchestration, not a Crossgen2 compiler bug.

Fix

Keep publish/ as the stable Crossgen2 input for every attempt.

For CoreCLR Mach-O R2R, the proxy now:

• recreates obj/R2R/ before compiling;
• creates obj/r2r-app-bundle-source/ from publish/ plus the current R2R output;
• points AppleBuildDir and the bundle item lists at that directory.

Crossgen2 and AppleAppBuilder output can no longer become input to a later retry, and partial output from a killed attempt is removed.

Regression coverage

The new Apple.Build.Tests host test runs the real proxy targets twice in the same temporary work-item directory. It verifies that:

• publish/ keeps the same files and contents;
• final bundle paths are declared before the bundle source is created;
• the bundle source contains exactly the publish inputs plus the current attempt's R2R output;
• files left by a killed or previous attempt are removed.

The test runs through the apple.buildtests subset on macOS x64 when Apple build files change and on non-PR rolling builds. It does not require an Apple SDK or device.

Validation

• ./build.sh -s apple.buildtests -c Release -test: 1 passed, 0 failed.
• An earlier form of the same staging fix ran System.Net.Security.Unit.Tests three times in one tvOS Helix work-item directory in build 1558829. All three attempts rebuilt R2R, launched the app, reached 128 tests, and had no stripped-IL or APP_CRASH failure. The work item remained red because of a separate certificate-context test failure.

Note

This description and change were prepared with GitHub Copilot assistance and reviewed by the submitting developer.

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[Copilot]

Pull request overview

This PR addresses a Helix retry hazard in Apple mobile CoreCLR test app ReadyToRun (R2R) compilation by preventing crossgen2 outputs from being written back into the publish/ directory (which is also the crossgen2 input). Instead, it stages a pristine app payload into an intermediate directory and overlays R2R outputs there, ensuring retries recompile from original IL inputs.

Changes:

• Introduces an obj/r2r-publish/ staging directory: copies the original publish/ payload into it, then overlays crossgen2 outputs, and builds the app bundle from the staged payload.
• Ensures retry safety by recreating the staging directory on every run and deleting obj/R2R before recompilation.
• Adds guardrails: warnings when R2R outputs are unexpectedly empty and a fail-fast error if stale *.r2r.dylib outputs are detected in publish/.

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Suppressed comments (1)

src/mono/wasm/Wasm.Build.Tests/AppleHelixR2RTests.cs:356

• ReplaceDirectoryContent uses TryDeleteDirectory, which swallows IOException/UnauthorizedAccessException. Since this method is intended to ensure the crossgen output directory is clean between attempts, suppressing delete failures can leave stale files behind and make the test nondeterministic (or validate the wrong behavior). It’s better to delete the directory deterministically (or fail) and then recreate/populate it.

    private static void ReplaceDirectoryContent(string directory, (string RelativePath, string Content)[] files)
    {
        TryDeleteDirectory(directory);
        foreach ((string relativePath, string content) in files)
            WriteFile(Path.Combine(directory, ToNativePath(relativePath)), content);

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Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

Suppressed comments (1)

src/mono/wasm/Wasm.Build.Tests/AppleHelixR2RTests.cs:378

• ReplaceDirectoryContent deletes the directory via TryDeleteDirectory, which silently swallows IOException/UnauthorizedAccessException. In this method that behavior can hide real test setup failures and leave stale files behind (e.g., if deletion fails on Windows due to file locks), potentially making the test flaky or misleading. Prefer a deterministic delete that fails the test when the directory cannot be cleared; keep TryDeleteDirectory only for best-effort cleanup in the finally path.

    private static void ReplaceDirectoryContent(string directory, (string RelativePath, string Content)[] files)
    {
        TryDeleteDirectory(directory);
        foreach ((string relativePath, string content) in files)
            WriteFile(Path.Combine(directory, ToNativePath(relativePath)), content);

[davidnguyen-tech]

/azp run runtime-extra-platforms

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Suppressed comments (2)

src/mono/msbuild/apple/tests/Apple.Build.Tests/AppleHelixR2RTests.cs:180

• RunAttempt has an unused parameter publishDir. This makes the helper signature misleading and may also trip analyzers if unused-parameter diagnostics are enabled. Consider removing the parameter and updating the two call sites accordingly.

    private void RunAttempt(
        string workItemRoot,
        string publishDir,
        string crossgenOutputDir,
        string r2rIntermediateDir,
        string appBundleSourceDir,
        (string RelativePath, string Content)[] r2rOutput)
    {

src/mono/msbuild/apple/data/ProxyProjectForAOTOnHelix.proj:188

• These steps assume $(_R2RAppBundleSourceDir) is set. Currently the target’s Condition is only PublishReadyToRunContainerFormat == macho, so invoking the target without the full R2R/CoreCLR predicates would leave _R2RAppBundleSourceDir empty and make RemoveDir/Copy behavior ambiguous. Add an explicit guard so the target fails fast if _R2RAppBundleSourceDir isn’t set.

    <!-- Recreated on every run so that a Helix retry in the same work item cannot inherit stale dylibs
         or app builder output from a previous attempt. -->
    <RemoveDir Directories="$(_R2RAppBundleSourceDir)" />
    <MakeDir Directories="$(_R2RAppBundleSourceDir)" />

[davidnguyen-tech]

/azp run runtime-extra-platforms

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Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.