[lewing]

Since #136234 (and with the handler fixes from #136261), System.Net.Http.Functional.Tests sets UseNativeHttpHandler=false on WASI, so it covers SocketsHttpHandler. The switch is process-wide and trimmed, so one assembly can't also test the wasi:http handler (WasiHttpHandler). This adds a WASI-only test project, System.Net.Http.WasiHttpHandler.Functional.Tests, that leaves the switch at its WASI default (true).

Test project

The project adds WasiHttpHandler_* classes for these shared test bases:

• HttpClientHandlerTest
• Asynchrony
• Cancellation
• IdnaProtocolTests
• PostScenarioTest
• ResponseStreamTest

It also includes HttpClientHandler_RemoteServerTest. PostScenarioTest and RemoteServerTest are OuterLoop on WASI.

The existing tests.proj glob picks the project up, which adds one Helix work item.

Skips

• Capability gates:
  • The AutoRedirect, Decompression, Proxy and DefaultProxyCredentials classes use ConditionalClass on SupportsRedirectConfiguration, SupportsAutomaticDecompression and SupportsProxy. Those probes now live in the shared HttpClientHandlerTestBase.
  • In-body checks cover the same capabilities.
• IsWasiHttpHandler (alongside IsWinHttpHandler) adds early returns for handler gaps with no public capability flag:
  • Credentials and PreAuthenticate
  • CookieContainer
  • MaxConnectionsPerServer
  • redirect following
  • synchronous stream I/O
• Host behaviour: wasmtime's wasi:http behaviour is also gated:
  • It forbids hop-by-hop request headers and control characters.
  • It strips hop-by-hop response headers and rejects obs-fold.
  • It doesn't expose the reason phrase or let the client choose the HTTP version.
• Outerloop helpers:
  • MD5 checks are gated on PlatformDetection.IsMD5Supported, using the echo server's existing Content-MD5-Skip path.
  • The HTTPS/HTTP2 local echo endpoints are dropped on WASI, which doesn't trust their dev certificate.

HttpProtocolTests isn't included: it checks status-line parsing that the wasi:http host performs, and Browser excludes it too.

Validation

CoreCLR WASI, Release, wasmtime 49.0.1, on main a932cb67bf6:

Suite	Run	Passed	Failed	Skipped
System.Net.Http.WasiHttpHandler.Functional.Tests	195	184	0	11
System.Net.Http.Functional.Tests (shared test changes)	1994	1810	0	184

Outerloop was validated before the rebase onto current main: 311 of 325 tests passed, with 0 failures, with every class except the two SupportsProxy-gated proxy classes.

Running the full outerloop scope still runs those proxy classes. WasmTestRunner lets -trait category=OuterLoop override -notrait category=failing, so ConditionalClass-gated classes run anyway. That's a separate runner issue affecting all WASI/browser projects. The WASI outerloop CI leg currently runs innerloop scope only.

Note

This PR description and the changes were generated with GitHub Copilot.

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