Add support for async/streams/futures

This adds support for loading, compiling, linking, and running components which
use the [Async
ABI](https://github.com/WebAssembly/component-model/blob/main/design/mvp/Async.md)
along with the [`stream`, `future`, and
`error-context`](WebAssembly/component-model#405) types.
It also adds support for generating host bindings such that multiple host
functions can be run concurrently with guest tasks -- without monopolizing the
`Store`.

See the [implementation RFC](bytecodealliance/rfcs#38)
for details, as well as [this
repo](https://github.com/dicej/component-async-demo) containing end-to-end smoke
tests.

This is very much a work-in progress, with a number of tasks remaining:

- [ ] Avoid exposing global task IDs to guests and use per-instance IDs instead
- [ ] Track `task.return` type during compilation and assert the actual and expected types match at runtime
- [ ] Ensure all guest pointers are bounds-checked when lifting, lowering, or copying values
- [ ] Reduce code duplication in `wasmtime_cranelift::compiler::component`
- [ ] Reduce code duplication between `StoreContextMut::on_fiber` and `concurrent::on_fiber`
- [ ] Minimize and/or document the use of unsafe code
- [ ] Add support for `(Typed)Func::call_concurrent` per the RFC
- [ ] Add support for multiplexing stream/future reads/writes and concurrent calls to guest exports per the RFC
- [ ] Refactor, clean up, and unify handling of backpressure, yields, and even polling
- [ ] Guard against reentrance where required (e.g. in certain fused adapter calls)
- [ ] Add integration test cases covering new functionality to tests/all/component_model (starting by porting over the tests in https://github.com/dicej/component-async-demo)
- [ ] Add binding generation test cases to crates/component-macro/tests
- [ ] Add WAST tests to tests/misc_testsuite/component-model
- [ ] Add support and test coverage for callback-less async functions (e.g. goroutines)
- [ ] Switch to back to upstream `wasm-tools` once bytecodealliance/wasm-tools#1895 has been merged and released

Signed-off-by: Joel Dice <joel.dice@fermyon.com>

Author: dicej

Cargo.lock

@@ -274,15 +274,15 @@ wit-bindgen = { version = "0.34.0", default-features = false }
 wit-bindgen-rust-macro = { version = "0.34.0", default-features = false }
 
 # wasm-tools family:
-wasmparser = { version = "0.219.1", default-features = false }
-wat = "1.219.1"
-wast = "219.0.1"
-wasmprinter = "0.219.1"
-wasm-encoder = "0.219.1"
-wasm-smith = "0.219.1"
-wasm-mutate = "0.219.1"
-wit-parser = "0.219.1"
-wit-component = "0.219.1"
+wasmparser = { git = "https://github.com/dicej/wasm-tools", branch = "async" }
+wat = { git = "https://github.com/dicej/wasm-tools", branch = "async" }
+wast = { git = "https://github.com/dicej/wasm-tools", branch = "async" }
+wasmprinter = { git = "https://github.com/dicej/wasm-tools", branch = "async" }
+wasm-encoder = { git = "https://github.com/dicej/wasm-tools", branch = "async" }
+wasm-smith = { git = "https://github.com/dicej/wasm-tools", branch = "async" }
+wasm-mutate = { git = "https://github.com/dicej/wasm-tools", branch = "async" }
+wit-parser = { git = "https://github.com/dicej/wasm-tools", branch = "async" }
+wit-component = { git = "https://github.com/dicej/wasm-tools", branch = "async" }
 
 # Non-Bytecode Alliance maintained dependencies:
 # --------------------------

Cargo.toml

@@ -41,3 +41,4 @@ similar = { workspace = true }
 [features]
 async = []
 std = ['wasmtime-wit-bindgen/std']
+component-model-async = ['std', 'async', 'wasmtime-wit-bindgen/component-model-async']

crates/component-macro/Cargo.toml

@@ -1,14 +1,15 @@
 use proc_macro2::{Span, TokenStream};
 use quote::ToTokens;
-use std::collections::HashMap;
-use std::collections::HashSet;
+use std::collections::{HashMap, HashSet};
 use std::env;
 use std::path::{Path, PathBuf};
 use std::sync::atomic::{AtomicUsize, Ordering::Relaxed};
 use syn::parse::{Error, Parse, ParseStream, Result};
 use syn::punctuated::Punctuated;
 use syn::{braced, token, Token};
-use wasmtime_wit_bindgen::{AsyncConfig, Opts, Ownership, TrappableError, TrappableImports};
+use wasmtime_wit_bindgen::{
+    AsyncConfig, CallStyle, Opts, Ownership, TrappableError, TrappableImports,
+};
 use wit_parser::{PackageId, Resolve, UnresolvedPackageGroup, WorldId};
 
 pub struct Config {
@@ -20,13 +21,22 @@ pub struct Config {
 }
 
 pub fn expand(input: &Config) -> Result<TokenStream> {
-    if !cfg!(feature = "async") && input.opts.async_.maybe_async() {
+    if let (CallStyle::Async | CallStyle::Concurrent, false) =
+        (input.opts.call_style(), cfg!(feature = "async"))
+    {
         return Err(Error::new(
             Span::call_site(),
             "cannot enable async bindings unless `async` crate feature is active",
         ));
     }
 
+    if input.opts.concurrent_imports && !cfg!(feature = "component-model-async") {
+        return Err(Error::new(
+            Span::call_site(),
+            "cannot enable `concurrent_imports` option unless `component-model-async` crate feature is active",
+        ));
+    }
+
     let mut src = match input.opts.generate(&input.resolve, input.world) {
         Ok(s) => s,
         Err(e) => return Err(Error::new(Span::call_site(), e.to_string())),
@@ -40,7 +50,10 @@ pub fn expand(input: &Config) -> Result<TokenStream> {
     // place a formatted version of the expanded code into a file. This file
     // will then show up in rustc error messages for any codegen issues and can
     // be inspected manually.
-    if input.include_generated_code_from_file || std::env::var("WASMTIME_DEBUG_BINDGEN").is_ok() {
+    if input.include_generated_code_from_file
+        || input.opts.debug
+        || std::env::var("WASMTIME_DEBUG_BINDGEN").is_ok()
+    {
         static INVOCATION: AtomicUsize = AtomicUsize::new(0);
         let root = Path::new(env!("DEBUG_OUTPUT_DIR"));
         let world_name = &input.resolve.worlds[input.world].name;
@@ -107,13 +120,15 @@ impl Parse for Config {
                     }
                     Opt::Tracing(val) => opts.tracing = val,
                     Opt::VerboseTracing(val) => opts.verbose_tracing = val,
+                    Opt::Debug(val) => opts.debug = val,
                     Opt::Async(val, span) => {
                         if async_configured {
                             return Err(Error::new(span, "cannot specify second async config"));
                         }
                         async_configured = true;
                         opts.async_ = val;
                     }
+                    Opt::ConcurrentImports(val) => opts.concurrent_imports = val,
                     Opt::TrappableErrorType(val) => opts.trappable_error_type = val,
                     Opt::TrappableImports(val) => opts.trappable_imports = val,
                     Opt::Ownership(val) => opts.ownership = val,
@@ -138,7 +153,7 @@ impl Parse for Config {
                                 "cannot specify a world with `interfaces`",
                             ));
                         }
-                        world = Some("interfaces".to_string());
+                        world = Some("wasmtime:component-macro-synthesized/interfaces".to_string());
 
                         opts.only_interfaces = true;
                     }
@@ -205,7 +220,7 @@ fn parse_source(
             };
             let (pkg, sources) = resolve.push_path(normalized_path)?;
             pkgs.push(pkg);
-            files.extend(sources);
+            files.extend(sources.package_paths(pkg).unwrap().map(|v| v.to_owned()));
         }
         Ok(())
     };
@@ -281,6 +296,8 @@ mod kw {
     syn::custom_keyword!(require_store_data_send);
     syn::custom_keyword!(wasmtime_crate);
     syn::custom_keyword!(include_generated_code_from_file);
+    syn::custom_keyword!(concurrent_imports);
+    syn::custom_keyword!(debug);
 }
 
 enum Opt {
@@ -301,12 +318,18 @@ enum Opt {
     RequireStoreDataSend(bool),
     WasmtimeCrate(syn::Path),
     IncludeGeneratedCodeFromFile(bool),
+    ConcurrentImports(bool),
+    Debug(bool),
 }
 
 impl Parse for Opt {
     fn parse(input: ParseStream<'_>) -> Result<Self> {
         let l = input.lookahead1();
-        if l.peek(kw::path) {
+        if l.peek(kw::debug) {
+            input.parse::<kw::debug>()?;
+            input.parse::<Token![:]>()?;
+            Ok(Opt::Debug(input.parse::<syn::LitBool>()?.value))
+        } else if l.peek(kw::path) {
             input.parse::<kw::path>()?;
             input.parse::<Token![:]>()?;
 
@@ -380,6 +403,10 @@ impl Parse for Opt {
                     span,
                 ))
             }
+        } else if l.peek(kw::concurrent_imports) {
+            input.parse::<kw::concurrent_imports>()?;
+            input.parse::<Token![:]>()?;
+            Ok(Opt::ConcurrentImports(input.parse::<syn::LitBool>()?.value))
         } else if l.peek(kw::ownership) {
             input.parse::<kw::ownership>()?;
             input.parse::<Token![:]>()?;

crates/component-macro/src/bindgen.rs

@@ -45,3 +45,4 @@ gc = ["wasmtime-environ/gc"]
 gc-drc = ["gc", "wasmtime-environ/gc-drc"]
 gc-null = ["gc", "wasmtime-environ/gc-null"]
 threads = ["wasmtime-environ/threads"]
+