Add support for pure WASIp2 builds

.github/workflows/ci.yml

@@ -115,22 +115,28 @@ jobs:
         run: just ${{ matrix.recipe }} --examples
 
   # ---------------------------------------------------------------------------
-  # Componentization suites against the debug runtime (`just test-componentize`).
-  # That recipe builds the runtime for wasm32-wasip3, the target the componentizer
-  # links against, so this job installs beta and a wasi-sdk with a sysroot for it.
+  # Componentization suites against the debug runtime (`just test-componentize`),
+  # built for each wasm target (`RUNTIME_TARGET`). A wasm32-wasip3 build needs
+  # beta and a wasi-sdk with a sysroot for it, which the setup action installs.
   # ---------------------------------------------------------------------------
   componentize:
-    name: Componentize
+    name: Componentize (${{ matrix.target }})
+    strategy:
+      fail-fast: false
+      matrix:
+        target: [wasm32-wasip2, wasm32-wasip3]
     runs-on: ubuntu-latest
     env:
+      RUNTIME_TARGET: ${{ matrix.target }}
+      WASM_TARGET: ${{ matrix.target }}
       WASMTIME_BACKTRACE_DETAILS: '1'
       RUST_BACKTRACE: 'full'
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
 
       - uses: ./.github/actions/setup
         with:
-          target: wasm32-wasip3
+          target: ${{ matrix.target }}
 
       - uses: actions/setup-node@949feb2413d6458794dcd2491c4babbbce0c15c1 # v7.1.0
         with:
@@ -149,7 +155,7 @@ jobs:
 
       # Snapshots with `wizer-initialize`, including CLI tools whose `run` export a snapshot calls.
       - name: Test Wizer snapshots
-        run: WASM_TARGET=p3 just test-wizer
+        run: just test-wizer
 
   # ---------------------------------------------------------------------------
   # WPT suite: {native, wasm32-wasip2, wasm32-wasip3}
@@ -205,8 +211,9 @@ jobs:
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
 
-      # `just check-gc` also checks the wasm32-wasip2 build, which needs the target's std and the
-      # WASI SDK, and runs crown's own tests.
+      # `just check-gc` also checks the wasm32-wasip2 and wasm32-wasip3 builds, which need the WASI
+      # SDK, and runs crown's own tests. Crown's toolchain, which rustup installs from
+      # `crown/rust-toolchain.toml`, brings both targets' std.
       - uses: ./.github/actions/setup
         with:
           target: wasm32-wasip2

Cargo.toml

@@ -19,6 +19,7 @@ exclude = ["crown"]
 resolver = "2"
 
 [workspace.dependencies]
+async-task = "4.7.1"
 bitflags = "2"
 bytes = "1"
 clap = { version = "4.5.60", features = ["derive"] }
@@ -48,10 +49,13 @@ smallvec = "1.16"
 starling-macro = { path = "crates/starling-macro" }
 tokio = { version = "1", features = ["rt", "time", "net", "io-util"] }
 url = "2.5.8"
+wasip2 = "2.0.1"
 wasip3 = { version = "0.9.0", features = ["http-compat"] }
 wasmparser = { version = "0.262", default-features = false, features = ["validate", "component-model"] }
-# Must equal the `wit-bindgen` version `wasip3` depends on. See `starling/Cargo.toml`.
-wit-bindgen = { version = "=0.62.0", features = ["macros"] }
+# Must equal the `wit-bindgen` version `wasip2` and `wasip3` depend on. See `starling/Cargo.toml`.
+# The async features are enabled only by the wasm32-wasip3 dependency tables, so a wasm32-wasip2
+# build uses none of the component model's async ABI.
+wit-bindgen = { version = "=0.62.0", default-features = false, features = ["macros", "realloc", "std", "bitflags", "macro-string"] }
 wit-bridge = { path = "crates/wit-bridge" }
 wit-name-mapping = { path = "crates/wit-name-mapping" }
 wpt-support = { path = "crates/wpt-support" }

README.md

@@ -26,6 +26,7 @@ JavaScript application and a WIT world.
   - [Components that serve and run](#components-that-serve-and-run)
   - [Initialization](#initialization)
   - [Refused worlds](#refused-worlds)
+  - [WASIp2 runtimes](#wasip2-runtimes)
   - [Disabling WASI features](#disabling-wasi-features)
   - [The interfaces the runtime imports](#the-interfaces-the-runtime-imports)
   - [WIT values in JavaScript](#wit-values-in-javascript)
@@ -415,6 +416,24 @@ Componentizing these worlds fails with an error naming the function or export:
 - a world that imports an interface at several compatible versions, from its own WIT or the
   runtime's, where a version lacks a type or function that a lower one declares.
 
+### WASIp2 support
+
+StarlingMonkey has full WASIp2 support, enabling it to run on hosts that don't support WASIp3
+interfaces or the Component Model's async functions, `future`s, and `stream`s.
+
+Besides using WASIp2 APIs and `wasi:io` for streaming, a key implication is that such a build
+doesn't support concurrent reuse, since incoming event handlers only return from the stack once
+they have fully finished processing the event, including any post-return work, such as 
+body-streaming and promises passed to `waitUntil`.
+
+The componentizer's CLI options, such as `--export-http`, automatically use the interface version
+the runtime targets. That is, a runtime built for `wasm32-wasip2` will export 
+`wasi:http/incoming-handler@0.2.0` with `--export-http` set.
+
+Trying to target a world with `async` functions, or using `stream` or `future`, will fail with a
+`wasm32-wasip2` runtime. That limitation could be lifted, though it's advisable to use a P3 runtime
+when targeting host environments that support WASIp3.
+
 ### Disabling WASI features
 
 `--disable` takes a comma-separated list of `stdio`, `random`, `clocks`, `http` and `filesystem`,
@@ -467,9 +486,11 @@ highest otherwise. Its types then have their plain names. A version that lacks a
 of a lower compatible version is [refused](#refused-worlds).
 
 A module specifier names an interface by its canonical version, as in `wasi:cli/environment@0.3`,
-and `starling-componentize imports` and the
-[TypeScript declarations](#typescript-declarations-for-a-world) name it that way. A specifier with
-any compatible full version, such as `wasi:cli/environment@0.3.0`, resolves to the same module.
+and `starling-componentize imports` and the [TypeScript
+declarations](#typescript-declarations-for-a-world) name it that way. A specifier with any
+compatible full version, such as `wasi:cli/environment@0.3.0`, resolves to the same module. A
+runtime built for WASIp2 imports its WASI interfaces at `0.2` versions, so the same import is
+spelled `wasi:cli/environment@0.2`.
 
 ### WIT values in JavaScript
 
@@ -1189,14 +1210,18 @@ just check-all         # more extensive tests, including GC checks
 `--workspace` by default. It accepts all additional arguments to `cargo test`,
 so to test specific packages, pass `-p [package name]`.
 
-**For WebAssembly (WASIp2):**
+**For WebAssembly:**
 
 ```bash
 just build-wasm        # debug build for wasm32-wasip2
 just test-wasm         # all Rust tests, on wasm32-wasip2
 just check-wasm        # fmt-check + clippy + wasm tests
 ```
 
+A wasm32-wasip2 build imports and exports only WASI 0.2 interfaces and uses none of the Component
+Model's async features. It runs on WASIp2 hosts, with the restrictions [WASIp2
+runtimes](#wasip2-runtimes) lists. A wasm32-wasip3 build imports and exports WASI 0.3 interfaces.
+
 `WASM_TARGET` selects the wasm target of the recipes above, the wasm WPT recipes and
 `just test-wizer`, as `p2`, `p3` or a full triple. It defaults to `p2`:
 
@@ -1218,8 +1243,8 @@ component `target/wasm32-wasip2/debug/starling.wasm` from the crate's `cdylib` t
 `target/wasm32-wasip3/release/starling.wasm`, with SpiderMonkey, libc and libc++ statically linked
 and dead-code eliminated. `just build-runtime-debug` builds it with `debugmozjs`, at
 `target/wasm32-wasip3/debug/starling.wasm`. `RUNTIME_TARGET` selects their target as `WASM_TARGET`
-does, and defaults to `p3`. `RUNTIME_TARGET=p2` builds for wasm32-wasip2 from the stable toolchain
-and an older SDK.
+does, and defaults to `p3`. `RUNTIME_TARGET=p2` builds the runtime for WASIp2 hosts, from the
+stable toolchain.
 
 The component runs scripts under `wasmtime run`, serves under `wasmtime serve`, and is the runtime
 `starling-componentize` links against. `just test-runtime` builds the debug component and runs two

componentize/Cargo.toml

@@ -59,7 +59,7 @@ mimalloc = "0.1.52"
 tokio = { version = "1", features = ["macros", "rt"] }
 proptest = "1.11"
 # `default-features = false` drops `default-send-request`, so no request reaches a real network.
-wasmtime-wasi-http = { version = "50", features = ["p3"], default-features = false }
+wasmtime-wasi-http = { version = "50", features = ["p2", "p3"], default-features = false }
 http = "1"
 http-body = "1"
 http-body-util = "0.1"

componentize/src/command.rs

@@ -47,7 +47,8 @@ const CLI_WORLD_NAME: &str = "command";
 /// The name of the world selected by `--export-http`, which exports
 /// `wasi:http/handler`. The interface is implemented by the application, or by
 /// the runtime, which dispatches each request to the `fetch` listeners that the
-/// application added while it was initialized.
+/// application added while it was initialized. A runtime built for WASIp2
+/// exports `wasi:http/incoming-handler` instead.
 const SERVE_WORLD_NAME: &str = "serve";
 
 /// The WIT sources of the worlds selected by `--export-cli` and
@@ -81,7 +82,11 @@ impl BuiltinWorlds {
             serve: builtin_world_wit(
                 "starling:serve",
                 SERVE_WORLD_NAME,
-                &interface(crate::HTTP_HANDLER_INTERFACE_PREFIX)?,
+                &interface(
+                    runtime
+                        .map_or(crate::WasiVersion::P3, crate::Runtime::wasi_version)
+                        .http_handler_prefix(),
+                )?,
             ),
         })
     }

componentize/src/finalize.rs

@@ -467,12 +467,14 @@ enum StubBody {
 }
 
 /// The body of the stub of `func` in the interface named `interface`: zeroes
-/// for a clock's `now`, the seed for `get-insecure-seed` if `insecure_seed` is
-/// set, and a trap for everything else.
+/// for a clock's `now`, the seed for `get-insecure-seed` (`insecure-seed` in
+/// WASI 0.2) if `insecure_seed` is set, and a trap for everything else.
 fn stub_body(interface: &str, func: &Function, insecure_seed: Option<u128>) -> StubBody {
     match (func.name.as_str(), insecure_seed) {
         ("now", _) if interface.starts_with("wasi:clocks/") => StubBody::Zero,
-        ("get-insecure-seed", Some(seed)) if interface.starts_with(INSECURE_SEED_INTERFACE) => {
+        ("get-insecure-seed" | "insecure-seed", Some(seed))
+            if interface.starts_with(INSECURE_SEED_INTERFACE) =>
+        {
             StubBody::Seed(seed)
         }
         _ => StubBody::Trap,