[release/6.0][wasm] Add support for native relinking after Build, and AOT after publish

[radical]

Wasm app build can run in two scenarios:

1. For build, eg. when running the app in VS, or dotnet build foo.csproj
2. For Publish, eg, when publishing the app to a folder, or Azure

A dotnet wasm app has some native wasm files (dotnet.wasm, and dotnet.js). How these files are obtained, or generated:

• Build

  • with no native libraries referenced (AOT setting is ignored here)
    • files from the runtime pack are used as-is
  • with native libraries referenced
    • dotnet.wasm is relinked with the native libraries

• Publish

  • dotnet.wasm is relinked with the native libraries, and updated pinvoke/icalls from the trimmed assemblies
  • if RunAOTCompilation=true, then the relinking includes AOT'ed assemblies

Build

Implementation:

• Target WasmBuildApp

• runs after Build by default

  • which can be disabled by $(DisableAutoWasmBuildApp)
  • or the run-after target can be set via $(WasmBuildAppAfterThisTarget)

• To run a custom target

  • before any of the wasm build targets, use $(WasmBuildAppDependsOn), and prepend your target name to that
  • after any of the wasm build targets, use AfterTargets="WasmBuildApp" on that target

• Avoid depending on this target, because it is available only when the workload is installed. Use $(WasmNativeWorkload) to check if it is installed.

Publish

Implementation:

• This part runs as a nested build using a MSBuild task, which means that the project gets reevaluated. So, if there were any changes made to items/properties in targets before this, then they won't be visible in the nested build.

• By default WasmTriggerPublishApp runs after the Publish target, and that triggers the nested build

  • The nested build runs WasmNestedPublishApp, which causes Build, and Publish targets to be run
  • Because this causes Build to be run again, if you have any targets that get triggered by that, then they will be running twice.
    • But the original build run, and this publish run can be differentiated using $(WasmBuildingForPublish)

• WasmTriggerPublishApp essentially just invokes the nested publish

  • This runs after Publish

    • which can be disabled by $(DisableAutoWasmPublishApp)
    • or the run-after target can be set via $(WasmTriggerPublishAppAfterThisTarget)

  • To influence the wasm build for publish, use WasmNestedPublishApp

    • To run a custom target before it, use $(WasmNestedPublishAppDependsOn)
    • to run a custom target after it, use AfterTargets="WasmNestedPublishApp"

  • If you want to dependsOn on this, then use DependsOnTargets="WasmTriggerPublishApp"

• Fixes [net6.0][BlazorWasmSdk] build does not link native files #56783

• Fixes If you build with trimming enabled, future builds with it disabled will produce incorrect output #53612

• Fixes [wasm] Avoid unnecessary linking after Build, when publishing from VS #58973

• Also fixes building for AOT with trimming disabled
  Fixes Cannot AOT compile with trimming disabled #53804