Add TypeScript Static Web Assets integration

[javiercn]

Summary

Fixes #51822, #52301

This PR adds support for integrating TypeScript outputs from the Microsoft.TypeScript.MSBuild NuGet package with ASP.NET Core Static Web Assets in Razor Class Libraries.

Problem

When using TypeScript with Static Web Assets in RCLs, rebuild operations fail because:

1. Timing issue: TypeScript compilation runs during the Compile phase, AFTER Static Web Assets discovery has already occurred
2. Stale references: During Clean, TypeScript targets delete the .js files, but Content items (added by Razor SDK globbing) persist in memory
3. Build failure: DefineStaticWebAssets then fails because it finds Content items referencing files that no longer exist

Solution

Added Microsoft.NET.Sdk.StaticWebAssets.TypeScript.targets which:

• Hooks into ResolveStaticWebAssetsInputsDependsOn to register TypeScript outputs AFTER compilation
• Removes TypeScript outputs from Content before CoreClean and ResolveProjectStaticWebAssets to prevent stale item references
• Uses DefineStaticWebAssets/DefineStaticWebAssetEndpoints for proper integration with compression, fingerprinting, and manifest generation
• Creates a manifest file (staticwebassets.typescript.files.txt) to track registered assets across builds

Changes

File	Description
Microsoft.NET.Sdk.StaticWebAssets.TypeScript.targets	New targets file with TypeScript integration logic
Microsoft.NET.Sdk.StaticWebAssets.targets	Added conditional import when TypeScript package is detected
TypeScriptIntegrationTest.cs	8 E2E integration tests
Microsoft.NET.Sdk.StaticWebAssets.Tests.csproj	Added assembly metadata for TypeScript version
eng/Versions.props	Added MicrosoftTypeScriptMSBuildPackageVersion
Directory.Packages.props	Added Microsoft.TypeScript.MSBuild package reference

Test Coverage

All 8 integration tests pass:

• ✅ Build_RegistersTypeScriptOutputsAsStaticWebAssets
• ✅ Build_TypeScriptOutputsAreProperlyCompressed
• ✅ Rebuild_SucceedsWithTypeScriptOutputs (main scenario from InvalidOperationException REBUILD fails due to "no file exists for the asset at either location" BUILD works #51822)
• ✅ Build_IncrementalBuild_WorksCorrectly
• ✅ Build_ModifyTypeScriptFile_UpdatesStaticWebAssets
• ✅ Publish_IncludesTypeScriptOutputs
• ✅ Clean_ThenBuild_SucceedsWithTypeScriptOutputs
• ✅ Build_TypeScriptDisabled_DoesNotRegisterAssets

How It Works

┌─────────────────────────────────────────────────────────────────────┐
│                         Build Pipeline                               │
├─────────────────────────────────────────────────────────────────────┤
│  1. ResolveCoreStaticWebAssets     (discovers existing wwwroot)     │
│  2. CompileTypeScriptWithTSConfig  (TypeScript → JS in wwwroot)     │
│  3. RegisterTypeScriptStaticWebAssets ◄── NEW: hooks in here        │
│     └─ DefineStaticWebAssets       (registers JS as SWA)            │
│     └─ DefineStaticWebAssetEndpoints (creates endpoint mappings)    │
│  4. Compression, fingerprinting, manifest generation                │
└─────────────────────────────────────────────────────────────────────┘

During rebuild, the RemoveTypeScriptFromContentBeforeSwaDiscovery target runs before CoreClean to prevent stale Content item references.

[javiercn]

Suggested change

	<!--
	Target: ResolveTypeScriptStaticWebAssetsConfiguration
	Sets up the path for the TypeScript manifest file.
	DependsOnTargets ResolveStaticWebAssetsConfiguration to ensure
	_StaticWebAssetsManifestBase is defined.
	-->

[javiercn]

Move this before the target definitions

[javiercn]

Suggested change

	<!--
	Write manifest file to track registered assets across builds.
	WriteOnlyWhenDifferent prevents unnecessary timestamp changes for incremental builds.
	FileWrites ensures the manifest is cleaned up during Clean target.
	-->

[javiercn]

Suggested change

	<!--
	Define endpoints for TypeScript assets.
	This creates the endpoint entries that map URL paths to assets,
	which are needed for the runtime to serve the files correctly.
	-->

[Copilot]

Pull request overview

This PR adds TypeScript Static Web Assets integration for Razor Class Libraries to fix rebuild failures when using the Microsoft.TypeScript.MSBuild NuGet package. The solution introduces a new targets file that properly registers TypeScript-compiled JavaScript outputs as static web assets after compilation completes.

Key Changes:

• Introduces RegisterTypeScriptStaticWebAssets target that hooks into the Static Web Assets pipeline to register TypeScript outputs after compilation
• Implements RemoveTypeScriptFromContentBeforeSwaDiscovery to prevent stale Content item references during rebuild operations
• Adds comprehensive E2E test coverage with 8 integration tests covering build, rebuild, clean, publish, and incremental build scenarios

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
Microsoft.NET.Sdk.StaticWebAssets.TypeScript.targets	New targets file implementing TypeScript/SWA integration with manifest tracking and proper cleanup
Microsoft.NET.Sdk.StaticWebAssets.targets	Conditional import of TypeScript targets when TypeScript package is detected
TypeScriptIntegrationTest.cs	Comprehensive test suite with 8 tests covering all key scenarios
Microsoft.NET.Sdk.StaticWebAssets.Tests.csproj	Assembly metadata for TypeScript package version configuration
Versions.props	TypeScript MSBuild package version definition (5.9.3)
Directory.Packages.props	Package version reference for central package management

[MackinnonBuck]

Looks great, just a small question about a test.

[MackinnonBuck]

Why is this needed? Does the test become flaky without it? Is there another way we can detect when the right conditions are met for the test to continue?