[pavelsavara]

Summary

• Build separate production and diagnostics trimmed shared-framework closures for CoreCLR browser WebAssembly.
• Generate and check in P/Invoke/QCall, reverse P/Invoke, and interpreter-to-managed helpers from each matching closure.
• Build separate production and diagnostics helper archives and select the matching archive while prelinking browserhost; runtime builds no longer regenerate the helpers.
• Package both managed closures and select the matching managed and native flavor without requiring wasm-tools.
• Keep diagnostics-compatible runtime-pack ReadyToRun images for the diagnostics build flavor; production build uses trimmed IL, while publish keeps app-specific trimming and optional ReadyToRun compilation.
• Treat EnableDiagnostics and EventSourceSupport as aliases for flavor selection without making either property independently trigger native relinking.

This is a stacked draft on #137014 and should be reviewed and merged after that PR.

Validation

• .\build.cmd -bl -os browser -subset clr+libs+host -c Debug /p:RuntimeFlavor=CoreCLR /p:EnableHotReloadInRuntimeConfigDevFile=false
  • Passed with 0 warnings and 0 errors.
• .\build.cmd -bl -os browser -subset clr+libs+host -c Release /p:RuntimeFlavor=CoreCLR /p:EnableHotReloadInRuntimeConfigDevFile=false
  • Passed with 0 warnings and 0 errors.
• CoreClrPrelinkedNativeFlavorIsSelectedWithoutWorkload
  • 6 passed, 0 failed, 0 skipped.
  • Covers default and explicit production/diagnostics build and publish selection, matching managed CoreLib selection, diagnostics-only prebuilt ReadyToRun, exact native hashes, and Chrome startup.
• TracingPropertySelectsNativeFlavor
  • 4 passed, 0 failed, 0 skipped.
  • Covers explicit tracing selection in plain Microsoft.NET.Sdk.WebAssembly projects.
• PropertyDifferentFromRuntimePackTriggersRelinking
  • 21 passed, 0 failed, 0 skipped.
  • Confirms tracing properties use exact prelinks without forcing relinking, while unrelated native property mismatches still relink.
• Full CoreCLRWasmNativeDefaultsTests
  • 39 passed, 0 failed, 0 skipped.
  • Covers the R2R directory/profile-flow cases that failed in the first CI run.
• Exact CI globalization regressions:
  • IdnMappingIdnaConformanceTests.GetAscii_Success passed in Chrome.
  • StringTests.IndexOf_NullInStrings is correctly skipped when Browser uses ICU; the first CI run incorrectly selected NLS behavior and executed it.
• BlazorEventPipeTestWithCpuSamplesPrelinked
  • 2 passed, 0 failed, 0 skipped.
• WebAssembly SDK pack and workload manifest package builds passed with 0 warnings and 0 errors.
• Canonical Release helper regeneration completed twice; all full, production, and diagnostics source hashes were unchanged on the second run.
• The runtime pack contains the full, production, and diagnostics helper archives. Production and diagnostics browserhost link responses contain only their matching archive and no generated helper objects.
• git diff --check, MSBuild XML parsing, and conflict-marker checks passed.

Release size comparison

Measurements are from the Release runtime-pack nupkg. Compressed values are the sum of the corresponding ZIP entry sizes.

Assets	Production raw	Diagnostics raw	Delta	Production compressed	Diagnostics compressed	Delta
Managed closure (181 assemblies)	21,662,720	21,699,584	+36,864	8,238,631	8,249,586	+10,955
Native trio	5,182,197	5,350,889	+168,692	1,897,775	1,956,899	+59,124
dotnet.native.wasm	4,418,991	4,573,643	+154,652	1,726,934	1,782,005	+55,071

System.Private.CoreLib.dll is 5,585,920 bytes in production and 5,600,768 bytes in diagnostics, a 14,848-byte difference.

The two additional checked-in helper archives add 794,822 raw bytes and 266,760 nupkg-compressed bytes. The existing full helper archive remains for corerun compatibility.

Reviewer notes

• The public EnableDiagnostics to EventSourceSupport migration is intentionally postponed.
• Both managed closures use ILLink all roots so they preserve the complete runtime implementation while applying EventSource feature substitutions. Production and diagnostics expose the same complete helper surface; their managed method bodies differ.
• Per-app helper generation remains in the workload relink path, where the application closure is not known ahead of time.
• Runtime-pack ReadyToRun remains diagnostics-compatible only. Production publish generates its selected trimmed and optional ReadyToRun closure as part of app publish.

Note

This pull request description was generated with GitHub Copilot.

[azure-pipelines]

Azure Pipelines:
Successfully started running 3 pipeline(s).
12 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[dotnet-policy-service]

Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
See info in area-owners.md if you want to be subscribed.