Changes in function-new_concurrent.rs

1e0b0b46 - Remove subtask reparenting (#12570)

Mon, 23 Feb 2026 21:00:21 +0000

Remove subtask reparenting (#12570)This commit updates the implementation of component-model-asyncprimitives to remove the manual subtask reparenting process. This isrequired to fix #12544 at a semantic level because a subtask isn't everactually reparented, even if its parent exits. The first part of thischange is to remove the `GuestTask::subtasks` field and all relevantmanipulations of it.This field, however, powered the `TaskExit` abstraction returned from`call_concurrent`. This commit then subsequently deletes `TaskExit` andall related infrastructure as it's no longer directly applicable as-is.The rest of this change is then updating tests/bindings/etc to accountfor these two changes.The main semantic changes related to tests are:* `wasmtime run`, with and without `--invoke`, no longer waits for all subtasks. This instead only waits for the main task returning before exiting. Whether or not this is the correct behavior is under discussion in WebAssembly/component-model#608* `wasmtime serve` has been updated to keep the store alive at least until the response body has been fully transmitted. This is also part of WebAssembly/component-model#608.* Some `component-async-tests`-related tests were updated to either avoid blocking the store as it wasn't needed or yield enough times to ensure that the test passes.Closes #12544prtest:full List of files: /wasmtime-44.0.1/crates/component-macro/tests/expanded/function-new_concurrent.rs

96e19700 - Migrate the `wasmtime` crate to `wasmtime_environ::error::*` (#12231)

Wed, 07 Jan 2026 17:08:11 +0000

Migrate the `wasmtime` crate to `wasmtime_environ::error::*` (#12231)* Migrate the `wasmtime` crate to `wasmtime_environ::error::*`Instead of `anyhow::Error`.This commit re-exports the `wasmtime_environ::error` as the `wasmtime::error`module, updates the prelude to include these new error-handling types, redirectsour top-level `wasmtime::{Error, Result}` re-exports to re-export`wasmtime::error::{Error, Result}`, and updates various use sites that weredirectly using `anyhow` to use the new `wasmtime` versions.This process also required updating the component macro and wit-bindgen macro touse the new error types instead of `anyhow`.Part of https://github.com/bytecodealliance/wasmtime/issues/12069* Replace wasmtime::error::Thing with wasmtime::Thing where it makes sense* cargo fmt* Move `crate::error::Thing` to `crate::Thing` where it makes sense List of files: /wasmtime-44.0.1/crates/component-macro/tests/expanded/function-new_concurrent.rs

080faa1a - add `task_exit` option to `wasmtime-wit-bindgen` (#11665)

Wed, 10 Sep 2025 20:27:13 +0000

add `task_exit` option to `wasmtime-wit-bindgen` (#11665)This builds on #11662 by optionally exposing the `TaskExit` return value from`[Typed]Func::call_concurrent` in the bindings generated for exported functions.Note that the first two commits are shared with #11662.Fixes #11600Signed-off-by: Joel Dice List of files: /wasmtime-44.0.1/crates/component-macro/tests/expanded/function-new_concurrent.rs

f75ae788 - return `TaskExit` future from `[Typed]Func::call_concurrent` (#11662)

Wed, 10 Sep 2025 16:37:25 +0000

return `TaskExit` future from `[Typed]Func::call_concurrent` (#11662)* return `TaskExit` future from `[Typed]Func::call_concurrent`In addition to returning the value produced by the callee, these functions nowalso return a `TaskExit` future which resolves once the subtask (and anytransitively-created subtasks) have exited. This partially addresses #11600;the next step will be to add a `wasmtime-wit-bindgen` option to expose the`TaskExit` value in generated bindings.Signed-off-by: Joel Dice * address review feedback`TaskExit` now has an `async fn block` instead of closing over an `implAsAccessor` and implementing `Future`.Signed-off-by: Joel Dice ---------Signed-off-by: Joel Dice List of files: /wasmtime-44.0.1/crates/component-macro/tests/expanded/function-new_concurrent.rs

1155d6df - Redesign function configuration in `bindgen!` (#11328)

Mon, 28 Jul 2025 18:31:06 +0000

Redesign function configuration in `bindgen!` (#11328)* Redesign function configuration in `bindgen!`This commit is a redesign of how function-level configuration works inWasmtime's `bindgen!` macro. The main goal of this redesign is tobetter support WASIp3 and component model async functions. Prior to thisredesign there was a mish mash of mechanisms to configure behavior ofimports/exports:* The `async` configuration could turn everything async, nothing async, only some imports async, or everything except some imports async.* The `concurrent_{imports,exports}` keys were required to explicitly opt-in to component model async signatures and applied to all imports/exports.* The `trappable_imports` configuration would indicate a list of imports allowed to trap and it had special configuration for everything, nothing, and only a certain list.* The `tracing` and `verbose_tracing` keys could be applied to either nothing or all functions.Overall the previous state of configuration in `bindgen!` was clearly ahodgepodge of systems that organically grew over time. In my personalopinion it was in dire need of a refresh to take into account howcomponent-model-async ended up being implemented as well asconsolidating the one-off systems amongst all of these configurationkeys. A major motivation of this redesign, for example, was to inheritbehavior from WIT files by default. An `async` function in WIT shouldnot require `concurrent_*` keys to be configured, but rather it shouldgenerate correct bindings by default.In this commit, all of the above keys were removed. All keys have beenreplaced with `imports` and `exports` configuration keys. Each behavesthe same way and looks like so: bindgen!({ // ... imports: { // enable tracing for just this function "my:local/interface/func": tracing, // enable verbose tracing for just this function "my:local/interface/other-func": tracing | verbose_tracing, // this is blocking in WIT, but generate async bindings for // it "my:local/interface/[method]io.block": async, // like above, but use "concurrent" bindings which have // access to the store. "my:local/interface/[method]io.block-again": async | store, // everything else is, by default, trappable default: trappable, }, });Effectively all the function-level configuration items are now bitflags.These bitflags are by default inherited from the WIT files itself (e.g.`async` functions are `async | store` by default). Further configurationis then layered on top at the desires of the embedder. Supported keys are:* `async` - this means that a Rust-level `async` function should be generated. This is either `CallStyle::Async` or `CallStyle::Concurrent` as it was prior, depending on ...* `store` - this means that the generated function will have access to the store on the host. This is only implemented right now for `async | store` functions which map to `CallStyle::Concurrent`. In the future I'd like to support just-`store` functions which means that you could define a synchronous function with access to the store in addition to an asynchronous function.* `trappable` - this means that the function returns a `wasmtime::Result`. If `trappable_errors` is applicable then it means just a `Result` is returned (like before)* `tracing` - this enables `tracing!` integration for this function.* `verbose_tracing` - this logs all argument values for this function (including lists).* `ignore_wit` - this ignores the WIT-level defaults of the function (e.g. ignoring WIT `async`).The way this then works is all modeled is that for any WIT functionbeing generated there are a set of flags associated with that function.To calculate the flags the algorithm looks like:1. Find the first matching rule in the `imports` or `exports` map depending on if the function is imported or exported. If there is no matching rule then use the `default` rule if present. This is the initial set of flags for the function (or empty if nothing was found).2. If `ignore_wit` is present, return the flags from step 1. Otherwise add in `async | store` if the function is `async` in WIT.The resulting set of flags are then used to control how everything isgenerated. For example the same split traits of today are stillgenerated and it's controlled based on the flags. Note though that theprevious `HostConcurrent` trait was renamed to `HostWithStore` to makespace for synchronous functions in this trait in the future too.The end result of all these changes is that configuring imports/exportsnow uses the exact same selection system as the `with` replacement map,meaning there's only one system of selecting functions instead of 3.WIT-level `async` is now respected by default meaning that bindings workby default without further need to configure anything (unless morefunctionality is desired).One final minor change made here as well is that auto-generated`instantiate` methods are now always synchronous and an`instantiate_async` method is unconditionally generated for async mode.This means that bindings always generate both functions and it's up tothe embedder to choose the appropriate one.Closes #11246Closes #11247* Update expanded test expectationsprtest:full* Fix the min platform embedding example* Fix doc tests* Always generate `*WithStore` traitsThis helps when using the `with` mapping since that can always assumethat `HostWithStore` is available in the generated bindings, avoidingthe need to duplicate configuration options.* Update test expectations* Review comments List of files: /wasmtime-44.0.1/crates/component-macro/tests/expanded/function-new_concurrent.rs

64bc3bd9 - Start to use `&Accessor` more in concurrent code (#11238)

Tue, 15 Jul 2025 15:14:02 +0000

Start to use `&Accessor` more in concurrent code (#11238)* Start to use `&Accessor` more in concurrent codeAfter discussion with Joel we've concluded that while `&mut Accessor`was originally added to model host functions it is also appropriate touse it to model embedder-rooted invocations of items such as wasm aswell. Effectively the conclusion we reached was that`*::call_concurrent` should be taking `&Accessor`, not`StoreContextMut`. This has a number of benefits to it over the previousiteration:* This makes exports behave more like imports where `Accessor` means "you're in the concurrent world".* This makes exports have an `async fn` signature which is easier to read and understand.* This automatically enforces the guarantee that the returned future is only polled within the main event loop because the future is always considered to close over the `&Accessor` provided meaning it statically cannot live outside of the event loop.* This paves the way forward to future refactorings to avoid storing so much state within a `Store` and instead try to store state directly in futures themselves. This should make cancellation more natural and eventually also remove `'static` bounds on params/results. Furthermore this should make it easier to avoid spawning tasks internally by storing state in futures instead of spawned tasks.In doing this one of the main questions we were faced with was what todo about `&mut Accessor`, namely the `mut` part. With a mutableaccessor it would be only possible to call one function concurrently.One option considered was to add combinators like `Accessor::join` and`Accessor::race` but in the end we decided to avoid going that directionand instead switch to `&Accessor` everywhere, freely enablingaliasing of the accessor. This has the downside that `Accessor::with` isnow a relatively dangerous function in that it can panic, but idiomaticusage of it is not expected to panic as the distinction between the`async` and sync boundary of `Accessor` vs `StoreContextMut` is expectedto naturally make the recursive panic condition of `with` rare to comeup in practice.Concrete changes in this commit are:* `Accessor::with` now requires `&self`.* `Accessor::spawn` now requires `&self`.* Host functions are now given `&Accessor`, not `&mut Accessor`.* `{Typed,}Func::call_concurrent` is now an `async fn` which takes an `&Accessor` instead of `StoreContextMut`.* Guest bindings generation for concurrent invocations now looks exactly like async bindings generation except for replacing `StoreContextMut` with `Accessor`.Note that this commit does not yet update the internal implementationsof these functions to benefit from the new abilities that taking`&Accessor` implies. Instead that's deferred to a future update asnecessary. Instead this is only updating the public API of the`wasmtime` crate to enable these refactorings in the future.Also note that this does not yet update all functions to take`&Accessor`. Notably futures and streams still need to be updated.cc #11224* Review comments---------Co-authored-by: Joel Dice List of files: /wasmtime-44.0.1/crates/component-macro/tests/expanded/function-new_concurrent.rs

beca86b0 - Re-enable concurrent bindings generation tests (#10972)

Mon, 09 Jun 2025 14:15:18 +0000

Re-enable concurrent bindings generation tests (#10972)* Re-enable concurrent bindings generation testsThis commit re-enables tests for bindings generation for concurrentcalls in the main repo after all syncs have now finished with wasip3.This additionally adds some skeleton APIs that the bindings generatoruses which are necessary to get tests passing.* Update test expectations List of files: /wasmtime-44.0.1/crates/component-macro/tests/expanded/function-new_concurrent.rs

f81c0dc0 - Add `T: 'static` to `Store` (#10760)

Tue, 13 May 2025 05:08:32 +0000

Add `T: 'static` to `Store` (#10760)* Add `T: 'static` to `StoreSince the beginning the `T` type parameter on `Store` has had nobounds on it. This was intended for maximal flexibility in terms of whatembedders place within a `Store` and I've personally advocated thatwe need to keep it this way. In the development of the WASIp3 work,however, I've at least personally reached the conclusion that this is nolonger tenable and proceeding will require adding a `'static` bound todata within a store.Wasmtime today [already] carries unsafe `transmute`s to work around thislack of `'static` bound, and while the number of `unsafe` parts isrelatively small right now we're still fundamentally lying to thecompiler about lifetime bounds internally. With the WASIp3 async workthis degree of "lying" has become even worse. Joel has written up someexamples [on Zulip] about how the Rust compiler is requiring `'static`bounds in surprising ways. These patterns are cropping up quitefrequently in the WASIp3 work and it's becoming particularly onerousmaintaining all of the `unsafe` and ensuring that everything is in sync.In the WASIp3 repository I've additionally [prototyped a change] whichwould additionally practically require `T: 'static` in more locations.This change is one I plan on landing in Wasmtime in the near future andwhile its main motivations are for enabling WASIp3 work it is also amuch nicer system than what we have today, in my opinion.Overall the cost of not having `T: 'static` on `Store` is effectivelybecoming quite costly, in particular with respect to WASIp3 work. Thisis coupled with all known embedders already using `T: 'static` datawithin a `Store` so the expectation of the impact of this change isnot large. The main downside of this change as a result is that when andwhere to place `'static` bounds is sort of a game of whack-a-mole withthe compiler. For example I changed `Store` to require `'static`here, but the rest of the change is basically "hit compile until rustcsays it's ok". There's not necessarily a huge amount of rhyme-or-reasonto where `'static` bounds crop up, which can be surprising or difficultto work with for users.In the end I feel that this change is necessary and one we can't shyaway from. If problems crop up we'll need to figure out how to threadthat needle at that time, but I'm coming around to thinking that`T: 'static` is just a fundamental constraint we'll have to take on atthis time. Maybe a future version of Rust that fixes some of Joel'sexamples (if they can be fixed, we're not sure of that) we couldconsider relaxing this but that's left for future work.[already]: https://github.com/bytecodealliance/wasmtime/blob/35053d6d8d1a5d4692cf636cba0c920b4a79a44b/crates/wasmtime/src/runtime/store.rs#L602-L611[on Zulip]: https://rust-lang.zulipchat.com/#narrow/channel/122651-general/topic/.22type.20may.20not.20live.20long.20enough.22.20for.20generic.20closure/near/473862072[prototyped a change]: https://github.com/bytecodealliance/wasip3-prototyping/pull/158* Remove a no-longer-necessary `unsafe` block* Update test expectations* Fix gc-disabled builds List of files: /wasmtime-44.0.1/crates/component-macro/tests/expanded/function-new_concurrent.rs

bb77f602 - wasmtime-wit-bindgen: Typecheck exports at {Foo}Indices construction (#10610)

Mon, 21 Apr 2025 21:54:01 +0000

wasmtime-wit-bindgen: Typecheck exports at {Foo}Indices construction (#10610)* wasmtime::component: make it possible to typecheck export funcs* wasmtime-wit-bindgen: add typechecking on construction of Indices struct* wit-bindgen: reduce to a single Indices constructor which takes InstancePre* bless bindgen output List of files: /wasmtime-44.0.1/crates/component-macro/tests/expanded/function-new_concurrent.rs

95cc0297 - Component and Instance have corresponding get_export, get_export_index (#10597)

Wed, 16 Apr 2025 21:38:26 +0000

Component and Instance have corresponding get_export, get_export_index (#10597)* component::Instance: get_export gives a ComponentItem, ExportIndex pairjust like Component::export_index does* align Instance and Component with get_export and get_export_index* fix example* component macro expanded: bless output* fix component model tests* cli only needs get_export_index* code review: deduplicate export to typedef transformation into ComponentItem::from_export List of files: /wasmtime-44.0.1/crates/component-macro/tests/expanded/function-new_concurrent.rs

636435f1 - async/stream/future support for wasmtime-wit-bindgen (#10044)

Wed, 22 Jan 2025 17:19:46 +0000

async/stream/future support for wasmtime-wit-bindgen (#10044)* async/stream/future support for wasmtime-wit-bindgenI've split this out of #9582 to make review easier.This patch adds async/stream/future/error-context support to the host bindinggenerator, along with placeholder type and function definitions in the`wasmtime` crate which the generated bindings can refer to. Seehttps://github.com/dicej/rfcs/blob/component-async/accepted/component-model-async.md#componentbindgen-updatesfor the design and rationale.Note that I've added temporary `[patch.crates-io]` overrides in Cargo.toml untilhttps://github.com/bytecodealliance/wit-bindgen/pull/1130 andhttps://github.com/bytecodealliance/wasm-tools/pull/1978 have been released.Also note that we emit a `T: 'static` bound for `AsContextMut` whengenerating bindings with `concurrent_imports: true`. This is only because`rustc` insists that the closure we're passing to`LinkerInstance::func_wrap_concurrent` captures the lifetime of `T` despite mybest efforts to convince it otherwise. Alex and I suspect this is a limitationin the compiler, and I asked about it on the rust-lang Zulip, but we haven'tbeen able to determine a workaround so far.Signed-off-by: Joel Dice remove obsolete TODO commentSigned-off-by: Joel Dice make `futures` dep optionalSigned-off-by: Joel Dice update `wasm-tools` and `wit-bindgen`Signed-off-by: Joel Dice * run cargo vetSigned-off-by: Joel Dice ---------Signed-off-by: Joel Dice List of files: /wasmtime-44.0.1/crates/component-macro/tests/expanded/function-new_concurrent.rs