[pavelsavara]

Summary

• Default StackTraceLineNumberSupport to false for browser publishing, including Debug publish, while preserving development-build defaults and explicit property values.
• Resolve WebAssembly feature configuration before publish trimming, including dotnet publish --no-build.
• Guard that early configuration so native-only nested publishes cannot write an incomplete boot manifest and shared completion stamp before the outer publish stages managed assemblies.
• Add browser regression coverage for build -> publish -> build, default behavior, explicit true/false, and publishing without rebuilding. Document source-location opt-in and symbol publishing.

This is a behavioral change: published CoreCLR managed stack traces keep method names, but source file/line lookup now requires explicit opt-in. The existing property restores the previous behavior:

<PropertyGroup>
  <StackTraceLineNumberSupport>true</StackTraceLineNumberSupport>
  <DebugSymbols>true</DebugSymbols>
  <CopyOutputSymbolsToPublishDirectory>true</CopyOutputSymbolsToPublishDirectory>
</PropertyGroup>

Breaking-change documentation has been prepared as a local draft; the source PR is not merged yet.

Size evidence

Using the source-built WebAssembly SDK pack with the same optimized 12.0.0-alpha.1.26528.120 browser runtime pack, a minimal trimmed Debug Blazor publish gives:

	Default publish	Explicit line-number opt-in
Linked managed assemblies	4	9
Linked managed bytes	2,373,632	2,614,784
Published *.wasm.gz bytes	2,703,287	2,807,850

The default removes exactly System.Collections.Immutable, System.Diagnostics.StackTrace, System.IO.Compression, System.IO.MemoryMappedFiles and System.Reflection.Metadata from both the linked closure and published WebCIL assets: 241,152 managed bytes and 104,563 gzip bytes saved. The consumed SDK target bytes were verified against the source-built package.

Locally built unoptimized Debug CoreLib can retain unreachable PDB-reader code after feature substitution. Size results above intentionally use an optimized shipping runtime pack; browser behavior tests use the locally built Debug runtime.

Validation

All commands ran from the isolated Windows worktree.

.\build.cmd -bl -os browser -subset clr+libs+host+packs -c Debug /p:RuntimeFlavor=CoreCLR /p:EnableHotReloadInRuntimeConfigDevFile=false

Passed: zero warnings/errors.

.\dotnet.cmd build -bl:artifacts\tmp\trimmed-closure\pack-final.binlog /p:TargetOS=browser /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Debug /p:EnableHotReloadInRuntimeConfigDevFile=false .\src\mono\nuget\Microsoft.NET.Sdk.WebAssembly.Pack\Microsoft.NET.Sdk.WebAssembly.Pack.pkgproj

Passed: zero warnings/errors.

.\dotnet.cmd build -bl:artifacts\tmp\trimmed-closure\wbt-green-final.binlog /p:TargetOS=browser /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Debug /p:TestUsingWorkloads=false /p:SdkVersionForWorkloadTesting=12.0.100-alpha.1.26528.120 /p:InstallWorkloadForTesting=false /p:EnableHotReloadInRuntimeConfigDevFile=false /p:InstallChromeForTests=false /p:XUnitClassName=Wasm.Build.Tests.DebugLevelTests /t:Test .\src\mono\wasm\Wasm.Build.Tests\Wasm.Build.Tests.csproj

Passed in Chrome: 6 passed, 0 failed, 0 skipped, including all four new cases and both existing trimmed-PDB cases. The new cases check actual source-line availability and retained method names across build/publish/build. Against the unchanged SDK package, the two new default-publish cases failed because source lines remained enabled; both explicit-override cases passed.

Two additional minimal publishes with the changed SDK package passed exact assertions for the linked and published five-assembly difference above. git diff --check passed.

The complete WBT suite, Mono runtime lane, and interactive managed debugger were not run.

Nested-publish CI follow-up

The early configuration dependency initially ran inside native-only nested publishes.
That generated an incomplete boot manifest before the outer publish staged managed
assemblies, then poisoned its shared incremental completion stamp. A guarded wrapper
now keeps the early dependency in the outer publish only; the original satellite and
reference preparation still runs in both contexts.

The existing workload LazyLoadingTests.FailOnMissingLazyAssembly reproduced
BLAZORSDK1001 with the unguarded package and passed with the guarded source-built
package. Existing coverage therefore catches this regression without adding redundant
tests.

.\dotnet.cmd build -bl:artifacts\tmp\trimmed-closure\nested-guard-pack.binlog /p:TargetOS=browser /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Debug /p:EnableHotReloadInRuntimeConfigDevFile=false .\src\mono\nuget\Microsoft.NET.Sdk.WebAssembly.Pack\Microsoft.NET.Sdk.WebAssembly.Pack.pkgproj

Passed: zero warnings/errors.

.\dotnet.cmd build -bl:artifacts\tmp\trimmed-closure\nested-existing-green.binlog /p:TargetOS=browser /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Debug /p:TestUsingWorkloads=true /p:SdkVersionForWorkloadTesting=12.0.100-alpha.1.26528.120 /p:InstallWorkloadForTesting=false /p:EnableHotReloadInRuntimeConfigDevFile=false /p:InstallChromeForTests=false /p:XUnitMethodName=Wasm.Build.Tests.LazyLoadingTests.FailOnMissingLazyAssembly /t:Test .\src\mono\wasm\Wasm.Build.Tests\Wasm.Build.Tests.csproj

Passed in Chrome: 1 passed, 0 failed, 0 skipped.

.\dotnet.cmd build -bl:artifacts\tmp\trimmed-closure\nested-noworkload-confirm.binlog /p:TargetOS=browser /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Debug /p:TestUsingWorkloads=false /p:SdkVersionForWorkloadTesting=12.0.100-alpha.1.26528.120 /p:InstallWorkloadForTesting=false /p:EnableHotReloadInRuntimeConfigDevFile=false /p:InstallChromeForTests=false /p:XUnitMethodName=Wasm.Build.Tests.DebugLevelTests.StackTraceLineNumbersBuildPublishBuild /t:Test .\src\mono\wasm\Wasm.Build.Tests\Wasm.Build.Tests.csproj

Passed in Chrome: 4 passed, 0 failed, 0 skipped, covering defaults, explicit
true/false, no-build publish, and build/publish/build. An initial run had one
ten-second harness exit-message timeout; that exact published opt-in artifact
independently printed source information, method name and WASM EXIT 0, and the
complete four-case confirmation above passed.

All consumed package targets matched the final source bytes. git diff --check
passed. The complete CI matrix and full Mono test lane have not been rerun locally.

Review follow-up: direct MSBuild publishing

The guarded publish target now applies the line-number default even when publishing
with dotnet msbuild -t:Publish, which does not supply _IsPublishing. Explicit
property values remain honored. The managed probe is now a standard
StackTraceTest scenario in WasmBasicTestApp, uses TestOutput.WriteLine, and the
theory uses the coreclr test category.

The expanded theory covers CLI and direct-MSBuild publishing, no-build publishing,
explicit true/false, and build/publish/build. Against the preceding package, both
direct-MSBuild default cases failed because source lines remained enabled; the
other six cases passed.

The source-built SDK package passed with zero warnings/errors:

.\dotnet.cmd build -bl:artifacts\tmp\trimmed-closure\review-pack.binlog /p:TargetOS=browser /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Debug /p:EnableHotReloadInRuntimeConfigDevFile=false .\src\mono\nuget\Microsoft.NET.Sdk.WebAssembly.Pack\Microsoft.NET.Sdk.WebAssembly.Pack.pkgproj

Final browser validation:

.\dotnet.cmd build -bl:artifacts\tmp\trimmed-closure\review-green.binlog /p:TargetOS=browser /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Debug /p:TestUsingWorkloads=false /p:SdkVersionForWorkloadTesting=12.0.100-alpha.1.26528.120 /p:InstallWorkloadForTesting=false /p:EnableHotReloadInRuntimeConfigDevFile=false /p:InstallChromeForTests=false /p:XUnitMethodName=Wasm.Build.Tests.DebugLevelTests.StackTraceLineNumbersBuildPublishBuild /t:Test .\src\mono\wasm\Wasm.Build.Tests\Wasm.Build.Tests.csproj

Passed in Chrome: 8 passed, 0 failed, 0 skipped.

.\dotnet.cmd build -bl:artifacts\tmp\trimmed-closure\review-nested-green.binlog /p:TargetOS=browser /p:TargetArchitecture=wasm /p:RuntimeFlavor=CoreCLR /p:Configuration=Debug /p:TestUsingWorkloads=true /p:SdkVersionForWorkloadTesting=12.0.100-alpha.1.26528.120 /p:InstallWorkloadForTesting=false /p:EnableHotReloadInRuntimeConfigDevFile=false /p:InstallChromeForTests=false /p:XUnitMethodName=Wasm.Build.Tests.LazyLoadingTests.FailOnMissingLazyAssembly /t:Test .\src\mono\wasm\Wasm.Build.Tests\Wasm.Build.Tests.csproj

Passed in Chrome: 1 passed, 0 failed, 0 skipped. Packaged target bytes match the
source; git diff --check passed.

Resolves #135222

Note

This PR was generated with assistance from GitHub Copilot.

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/ba-g known windows infra