[wasm] Restore net472 multi-targeting for WasmAppBuilder; fix Type.IsFunctionPointer compile break

[Copilot]

WasmAppBuilder was changed to single-target ($(NetCoreAppToolCurrent) only), breaking net472 builds needed for full-framework MSBuild hosts (Visual Studio). Type.IsFunctionPointer — a .NET 7+ API — was also used directly in the CoreCLR generator, causing a compile error on net472.

Changes

WasmAppBuilder.csproj — restore multi-targeting to match the pre-#122007 structure (with the sole exception of the todo-pinvoke-helpers.cpp → callhelpers-reverse.cpp rename already present on main):

• <TargetFramework> → <TargetFrameworks>$(NetCoreAppToolCurrent);$(NetFrameworkToolCurrent)
• Restore <Nullable>enable</Nullable>
• Restore per-TFM NoWarn conditions: CA1050/CS8604/CS8602 suppressed for .NETFramework; CA1050/CA1850 suppressed for non-.NETFramework (no unconditional NoWarn line)
• Restore .NETFramework compile includes (IsExternalInit.cs — needed for init setters in PInvokeCollector.cs — and NullableAttributes.cs) with the original $(RepoRoot)src\libraries\System.Private.CoreLib/... path
• Keep RuntimeFlavor == 'Mono' condition (uppercase, unchanged from main)
• Split Microsoft.Build.Tasks.Core PackageDownloadAndReference into per-TFM entries (ref/net472 / ref/net8.0) with IsTargetFrameworkCompatible guards (restored from pre-[wasm][coreclr] 2nd part of call helpers generator, reverse calls #122007)
• Restore GetFilesToPackage with explicit $(OutputPath)$(NetCoreAppToolCurrent)\... paths and $(NetFrameworkToolCurrent)\* dependent-assembly glob
• Restore UsingTask pointing to $(OutputPath)$(NetCoreAppToolCurrent)\WasmAppBuilder.dll without Runtime="NET"

coreclr/PInvokeTableGenerator.cs — replace direct Type.IsFunctionPointer usage with a reflection-based helper (mirrors the existing helper in mono/PInvokeTableGenerator.cs):

public static bool IsFunctionPointer(Type type)
{
    object? bIsFunctionPointer = type.GetType().GetProperty("IsFunctionPointer")?.GetValue(type);
    return (bIsFunctionPointer is bool b) && b;
}

Both PickCTypeNameForUnknownType and IsBlittableUncached now call IsFunctionPointer(t) instead of t.IsFunctionPointer.

coreclr/SignatureMapper.cs — same: replace t.IsFunctionPointer with PInvokeTableGenerator.IsFunctionPointer(t).

Runtime behavior on net10.0 is unchanged — reflection resolves to the same property.

Original prompt

Create a PR in dotnet/runtime that reverts the removal of multi-targeting from the WasmAppBuilder task project and fixes net472 compilation issues around PInvokeTableGenerator.IsFunctionPointer.

Context:

• The current src/tasks/WasmAppBuilder/WasmAppBuilder.csproj is single-targeting via <TargetFramework>$(NetCoreAppToolCurrent)</TargetFramework>.
• We need to restore the previous multi-targeting (likely via <TargetFrameworks>...), so that the task assembly can compile for net472 again.
• There is also a compile break for net472 due to use of Type.IsFunctionPointer in the CoreCLR-flavor generator.

Required changes:

1. Revert single-targeting in src/tasks/WasmAppBuilder/WasmAppBuilder.csproj back to multi-targeting.

   • Restore <TargetFrameworks> instead of <TargetFramework>.
   • Use the same TFMs as before the regression (determine by git history / blame / previous commits on that file). If unclear, prefer including net472 plus the existing $(NetCoreAppToolCurrent) (or the repo-standard property for the other TFM) to match prior behavior.
   • Ensure packaging target GetFilesToPackage still produces the expected output layout and includes all target outputs appropriately.

2. Make src/tasks/WasmAppBuilder/coreclr/PInvokeTableGenerator.cs compile on net472.

   • Replace direct use of type.IsFunctionPointer with a reflection-based helper similar to the one in src/tasks/WasmAppBuilder/mono/PInvokeTableGenerator.cs:
     • public static bool IsFunctionPointer(Type type) that uses type.GetType().GetProperty("IsFunctionPointer")?.GetValue(type).
   • Update the blittable checks / mapping code that currently references type.IsFunctionPointer to use the helper.
   • Keep runtime behavior equivalent on newer TFMs.

3. Add/adjust any conditional compilation if necessary so the code continues to build for non-net472 TFMs without warnings.

4. Add or update tests if there are existing build/test projects that cover the generator; at minimum, ensure the project builds for all target frameworks.

Notes:

• The PR should be minimal and focused: restore multi-targeting and fix the IsFunctionPointer net472 compile issue.
• Please include a clear PR title and description explaining why multi-targeting is needed and what was reverted.

Relevant files:

• src/tasks/WasmAppBuilder/WasmAppBuilder.csproj
• src/tasks/WasmAppBuilder/coreclr/PInvokeTableGenerator.cs
• (reference for helper) src/tasks/WasmAppBuilder/mono/PInvokeTableGenerator.cs

Reference PR for nearby changes:

• [wasm][coreclr] 2nd part of call helpers generator, reverse calls #122007

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: Revert the remove of multi-targeting from WasmAppBuilder.csproj

Assistant: I found the current WasmAppBuilder.csproj at:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>$(NetCoreAppToolCurrent)</TargetFramework>
    <NoWarn>$(NoWarn),CA1050,CA1850</NoWarn>
    <EnableSingleFileAnalyzer>false</EnableSingleFileAnalyzer>
    <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
  </PropertyGroup>

…but with the tools available here I could not locate the specific prior commit/PR where multi-targeting (<TargetFrameworks>...) was removed, nor retrieve the previous file version/diff (the searches came back empty / incomplete, and the commit-diff attempt didn’t return a usable diff).

What I need from you to do the revert correctly

Please provide one of the following, and I can produce the exact patch (or open a PR if you ask):

1. The commit SHA (or PR number) that removed multi-targeting from src/tasks/WasmAppBuilder/WasmAppBuilder.csproj, or
2. A link to the “History” view of that file showing the change (copy/paste the commit link), or
3. Tell me what the multi-targeting used to be (e.g. net8.0;net9.0 or $(NetCoreAppToolCurrent);$(NetCoreAppToolPrevious) etc).

Quick pointer

You can find it quickly via GitHub UI history:

• src/tasks/WasmAppBuilder/WasmAppBuilder.csproj → History → look for the commit that changed TargetFrameworks to TargetFramework.

Also note: the code-search results I got are limited and may be incomplete. If you want to dig via UI search, try:
https://github.com/dotnet/runtime/search?q=path%3Asrc%2Ftasks%2FWasmAppBuilder%2FWasmAppBuilder.csproj+TargetFrameworks&type=commits

Once you paste the commit/old TargetFrameworks line, I’ll generate the exact reverted WasmAppBuilder.csproj content.

User: There will also be a need to revert part around PInvokeTableGenerator.IsFunctionPointer to make the assembly compile for net472

Assistant: To make this compile for net472, the immediate problem area is that t...

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[radekdoulik]

Thank you, LGTM

[Copilot]

Pull request overview

This PR restores net472 multi-targeting for the WasmAppBuilder task project that was inadvertently removed in PR #122007, and fixes a compile break caused by direct use of Type.IsFunctionPointer (a .NET 7+ API) in the CoreCLR PInvoke generator code.

Changes:

• Restore <TargetFrameworks> to include both $(NetCoreAppToolCurrent) and $(NetFrameworkToolCurrent), along with per-TFM NoWarn conditions, .NETFramework compile includes, and packaging target adjustments.
• Replace direct Type.IsFunctionPointer calls in coreclr/PInvokeTableGenerator.cs and coreclr/SignatureMapper.cs with a reflection-based helper, mirroring the existing pattern in mono/PInvokeTableGenerator.cs.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
WasmAppBuilder.csproj	Restore multi-targeting, nullable settings, per-TFM warning suppression, framework-specific compile includes, per-TFM PackageDownloadAndReference, packaging target, and UsingTask path
coreclr/PInvokeTableGenerator.cs	Add reflection-based IsFunctionPointer helper; replace direct API calls
coreclr/SignatureMapper.cs	Replace t.IsFunctionPointer with PInvokeTableGenerator.IsFunctionPointer(t)

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