1 //! # Embedding API for the Component Model
2 //!
3 //! This module contains the embedding API for the [Component Model] in
4 //! Wasmtime. This module requires the `component-model` feature to be enabled,
5 //! which is enabled by default. The embedding API here is mirrored after the
6 //! core wasm embedding API at the crate root and is intended to have the same
7 //! look-and-feel while handling concepts of the component model.
8 //!
9 //! [Component Model]: https://component-model.bytecodealliance.org
10 //!
11 //! The component model is a broad topic which can't be explained here fully, so
12 //! it's recommended to read over individual items' documentation to see more
13 //! about the capabilities of the embedding API. At a high-level, however,
14 //! perhaps the most interesting items in this module are:
15 //!
16 //! * [`Component`] - a compiled component ready to be instantiated. Similar to
17 //!   a [`Module`](crate::Module) for core wasm.
18 //!
19 //! * [`Linker`] - a component-style location for defining host functions. This
20 //!   is not the same as [`wasmtime::Linker`](crate::Linker) for core wasm
21 //!   modules.
22 //!
23 //! * [`bindgen!`] - a macro to generate Rust bindings for a [WIT] [world]. This
24 //!   maps all WIT types into Rust automatically and generates traits for
25 //!   embedders to implement.
26 //!
27 //! [WIT]: https://component-model.bytecodealliance.org/design/wit.html
28 //! [world]: https://component-model.bytecodealliance.org/design/worlds.html
29 //!
30 //! Embedders of the component model will typically start by defining their API
31 //! in [WIT]. This describes what will be available to guests and what needs to
32 //! be provided to the embedder by the guest. This [`world`][world] that was
33 //! created is then fed into [`bindgen!`] to generate types and traits for the
34 //! embedder to use. The embedder then implements these traits, adds
35 //! functionality via the generated `add_to_linker` method (see [`bindgen!`] for
36 //! more info), and then instantiates/executes a component.
37 //!
38 //! It's recommended to read over the [documentation for the Component
39 //! Model][Component Model] to get an overview about how to build components
40 //! from various languages.
41 //!
42 //! ## Example Usage
43 //!
44 //! Imagine you have the following WIT package definition in a file called world.wit
45 //! along with a component (my_component.wasm) that targets `my-world`:
46 //!
47 //! ```text,ignore
48 //! package component:my-package;
49 //!
50 //! world my-world {
51 //!     import name: func() -> string;
52 //!     export greet: func() -> string;
53 //! }
54 //! ```
55 //!
56 //! You can instantiate and call the component like so:
57 //!
58 //! ```
59 //! fn main() -> wasmtime::Result<()> {
60 //!     #   if true { return Ok(()) }
61 //!     // Instantiate the engine and store
62 //!     let engine = wasmtime::Engine::default();
63 //!     let mut store = wasmtime::Store::new(&engine, ());
64 //!
65 //!     // Load the component from disk
66 //!     let bytes = std::fs::read("my_component.wasm")?;
67 //!     let component = wasmtime::component::Component::new(&engine, bytes)?;
68 //!
69 //!     // Configure the linker
70 //!     let mut linker = wasmtime::component::Linker::new(&engine);
71 //!     // The component expects one import `name` that
72 //!     // takes no params and returns a string
73 //!     linker
74 //!         .root()
75 //!         .func_wrap("name", |_store, _params: ()| {
76 //!             Ok((String::from("Alice"),))
77 //!         })?;
78 //!
79 //!     // Instantiate the component
80 //!     let instance = linker.instantiate(&mut store, &component)?;
81 //!
82 //!     // Call the `greet` function
83 //!     let func = instance.get_func(&mut store, "greet").expect("greet export not found");
84 //!     let mut result = [wasmtime::component::Val::String("".into())];
85 //!     func.call(&mut store, &[], &mut result)?;
86 //!
87 //!     // This should print out `Greeting: [String("Hello, Alice!")]`
88 //!     println!("Greeting: {:?}", result);
89 //!
90 //!     Ok(())
91 //! }
92 //! ```
93 //!
94 //! Manually configuring the linker and calling untyped component exports is
95 //! a bit tedious and error prone. The [`bindgen!`] macro can be used to
96 //! generate bindings eliminating much of this boilerplate.
97 //!
98 //! See the docs for [`bindgen!`] for more information on how to use it.
99 
100 #![cfg_attr(docsrs, doc(cfg(feature = "component-model")))]
101 // rustdoc appears to lie about a warning above, so squelch it for now.
102 #![allow(rustdoc::redundant_explicit_links)]
103 
104 mod component;
105 mod func;
106 mod instance;
107 mod linker;
108 mod matching;
109 mod resource_table;
110 mod resources;
111 mod storage;
112 mod store;
113 pub mod types;
114 mod values;
115 pub use self::component::Component;
116 pub use self::func::{
117     ComponentNamedList, ComponentType, Func, Lift, Lower, TypedFunc, WasmList, WasmStr,
118 };
119 pub use self::instance::{ExportInstance, Exports, Instance, InstancePre};
120 pub use self::linker::{Linker, LinkerInstance};
121 pub use self::resource_table::{ResourceTable, ResourceTableError};
122 pub use self::resources::{Resource, ResourceAny};
123 pub use self::types::{ResourceType, Type};
124 pub use self::values::Val;
125 
126 pub(crate) use self::resources::HostResourceData;
127 
128 // These items are expected to be used by an eventual
129 // `#[derive(ComponentType)]`, they are not part of Wasmtime's API stability
130 // guarantees
131 #[doc(hidden)]
132 pub mod __internal {
133     pub use super::func::{
134         bad_type_info, format_flags, lower_payload, typecheck_enum, typecheck_flags,
135         typecheck_record, typecheck_variant, ComponentVariant, LiftContext, LowerContext,
136         MaybeUninitExt, Options,
137     };
138     pub use super::matching::InstanceType;
139     pub use crate::map_maybe_uninit;
140     pub use crate::store::StoreOpaque;
141     pub use anyhow;
142     #[cfg(feature = "async")]
143     pub use async_trait::async_trait;
144     pub use wasmtime_environ;
145     pub use wasmtime_environ::component::{CanonicalAbiInfo, ComponentTypes, InterfaceType};
146 }
147 
148 pub(crate) use self::store::ComponentStoreData;
149 
150 /// Generate bindings for a [WIT world].
151 ///
152 /// [WIT world]: https://component-model.bytecodealliance.org/design/worlds.html
153 /// [WIT package]: https://component-model.bytecodealliance.org/design/packages.html
154 ///
155 /// This macro ingests a [WIT world] and will generate all the necessary
156 /// bindings for instantiating components that ascribe to the `world`. This
157 /// provides a higher-level representation of working with a component than the
158 /// raw [`Instance`] type which must be manually-type-checked and manually have
159 /// its imports provided via the [`Linker`] type.
160 ///
161 /// The most basic usage of this macro is:
162 ///
163 /// ```rust,ignore
164 /// wasmtime::component::bindgen!();
165 /// ```
166 ///
167 /// This will parse your projects [WIT package] in a `wit` directory adjacent to
168 /// your crate's `Cargo.toml`. All of the `*.wit` files in that directory are
169 /// parsed and then the single `world` found will be used for bindings.
170 ///
171 /// For example if your project contained:
172 ///
173 /// ```text,ignore
174 /// // wit/my-component.wit
175 ///
176 /// package my:project;
177 ///
178 /// world hello-world {
179 ///     import name: func() -> string;
180 ///     export greet: func();
181 /// }
182 /// ```
183 ///
184 /// Then you can interact with the generated bindings like so:
185 ///
186 /// ```rust
187 /// use wasmtime::component::*;
188 /// use wasmtime::{Config, Engine, Store};
189 ///
190 /// # const _: () = { macro_rules! bindgen { () => () }
191 /// bindgen!();
192 /// # };
193 /// # bindgen!({
194 /// #   inline: r#"
195 /// #       package my:project;
196 /// #       world hello-world {
197 /// #           import name: func() -> string;
198 /// #           export greet: func();
199 /// #       }
200 /// #   "#,
201 /// # });
202 ///
203 /// struct MyState {
204 ///     name: String,
205 /// }
206 ///
207 /// // Imports into the world, like the `name` import for this world, are
208 /// // satisfied through traits.
209 /// impl HelloWorldImports for MyState {
210 ///     // Note the `Result` return value here where `Ok` is returned back to
211 ///     // the component and `Err` will raise a trap.
212 ///     fn name(&mut self) -> String {
213 ///         self.name.clone()
214 ///     }
215 /// }
216 ///
217 /// fn main() -> wasmtime::Result<()> {
218 /// #   if true { return Ok(()) }
219 ///     // Configure an `Engine` and compile the `Component` that is being run for
220 ///     // the application.
221 ///     let mut config = Config::new();
222 ///     config.wasm_component_model(true);
223 ///     let engine = Engine::new(&config)?;
224 ///     let component = Component::from_file(&engine, "./your-component.wasm")?;
225 ///
226 ///     // Instantiation of bindings always happens through a `Linker`.
227 ///     // Configuration of the linker is done through a generated `add_to_linker`
228 ///     // method on the bindings structure.
229 ///     //
230 ///     // Note that the closure provided here is a projection from `T` in
231 ///     // `Store<T>` to `&mut U` where `U` implements the `HelloWorldImports`
232 ///     // trait. In this case the `T`, `MyState`, is stored directly in the
233 ///     // structure so no projection is necessary here.
234 ///     let mut linker = Linker::new(&engine);
235 ///     HelloWorld::add_to_linker(&mut linker, |state: &mut MyState| state)?;
236 ///
237 ///     // As with the core wasm API of Wasmtime instantiation occurs within a
238 ///     // `Store`. The bindings structure contains an `instantiate` method which
239 ///     // takes the store, component, and linker. This returns the `bindings`
240 ///     // structure which is an instance of `HelloWorld` and supports typed access
241 ///     // to the exports of the component.
242 ///     let mut store = Store::new(
243 ///         &engine,
244 ///         MyState {
245 ///             name: "me".to_string(),
246 ///         },
247 ///     );
248 ///     let (bindings, _) = HelloWorld::instantiate(&mut store, &component, &linker)?;
249 ///
250 ///     // Here our `greet` function doesn't take any parameters for the component,
251 ///     // but in the Wasmtime embedding API the first argument is always a `Store`.
252 ///     bindings.call_greet(&mut store)?;
253 ///     Ok(())
254 /// }
255 /// ```
256 ///
257 /// The function signatures within generated traits and on generated exports
258 /// match the component-model signatures as specified in the WIT `world` item.
259 /// Note that WIT also has support for importing and exports interfaces within
260 /// worlds, which can be bound here as well:
261 ///
262 /// For example this WIT input
263 ///
264 /// ```text,ignore
265 /// // wit/my-component.wit
266 ///
267 /// package my:project;
268 ///
269 /// interface host {
270 ///     gen-random-integer: func() -> u32;
271 ///     sha256: func(bytes: list<u8>) -> string;
272 /// }
273 ///
274 /// world hello-world {
275 ///     import host;
276 ///
277 ///     export demo: interface {
278 ///         run: func();
279 ///     }
280 /// }
281 /// ```
282 ///
283 /// Then you can interact with the generated bindings like so:
284 ///
285 /// ```rust
286 /// use wasmtime::component::*;
287 /// use wasmtime::{Config, Engine, Store};
288 /// use my::project::host::Host;
289 ///
290 /// # const _: () = { macro_rules! bindgen { () => () }
291 /// bindgen!();
292 /// # };
293 /// # bindgen!({
294 /// #   inline: r#"
295 /// # package my:project;
296 /// #
297 /// # interface host {
298 /// #     gen-random-integer: func() -> u32;
299 /// #     sha256: func(bytes: list<u8>) -> string;
300 /// # }
301 /// #
302 /// # world hello-world {
303 /// #     import host;
304 /// #
305 /// #     export demo: interface {
306 /// #         run: func();
307 /// #     }
308 /// # }
309 /// #   "#,
310 /// # });
311 ///
312 /// struct MyState {
313 ///     // ...
314 /// }
315 ///
316 /// // Note that the trait here is per-interface and within a submodule now.
317 /// impl Host for MyState {
318 ///     fn gen_random_integer(&mut self) -> u32 {
319 /// #       panic!();
320 /// #       #[cfg(FALSE)]
321 ///         rand::thread_rng().gen()
322 ///     }
323 ///
324 ///     fn sha256(&mut self, bytes: Vec<u8>) -> String {
325 ///         // ...
326 /// #       panic!()
327 ///     }
328 /// }
329 ///
330 /// fn main() -> wasmtime::Result<()> {
331 /// #   if true { return Ok(()) }
332 ///     let mut config = Config::new();
333 ///     config.wasm_component_model(true);
334 ///     let engine = Engine::new(&config)?;
335 ///     let component = Component::from_file(&engine, "./your-component.wasm")?;
336 ///
337 ///     let mut linker = Linker::new(&engine);
338 ///     HelloWorld::add_to_linker(&mut linker, |state: &mut MyState| state)?;
339 ///
340 ///     let mut store = Store::new(
341 ///         &engine,
342 ///         MyState { /* ... */ },
343 ///     );
344 ///     let (bindings, _) = HelloWorld::instantiate(&mut store, &component, &linker)?;
345 ///
346 ///     // Note that the `demo` method returns a `&Demo` through which we can
347 ///     // run the methods on that interface.
348 ///     bindings.demo().call_run(&mut store)?;
349 ///     Ok(())
350 /// }
351 /// ```
352 ///
353 /// The generated bindings can additionally be explored more fully with `cargo
354 /// doc` to see what types and traits and such are generated.
355 ///
356 /// # Syntax
357 ///
358 /// This procedural macro accepts a few different syntaxes. The primary purpose
359 /// of this macro is to locate a WIT package, parse it, and then extract a
360 /// `world` from the parsed package. There are then codegen-specific options to
361 /// the bindings themselves which can additionally be specified.
362 ///
363 /// Usage of this macro looks like:
364 ///
365 /// ```rust,ignore
366 /// // Parse the `wit/` folder adjacent to this crate's `Cargo.toml` and look
367 /// // for a single `world` in it. There must be exactly one for this to
368 /// // succeed.
369 /// bindgen!();
370 ///
371 /// // Parse the `wit/` folder adjacent to this crate's `Cargo.toml` and look
372 /// // for the world `foo` contained in it.
373 /// bindgen!("foo");
374 ///
375 /// // Parse the folder `other/wit/folder` adjacent to `Cargo.toml`.
376 /// bindgen!(in "other/wit/folder");
377 /// bindgen!("foo" in "other/wit/folder");
378 ///
379 /// // Parse the file `foo.wit` as a single-file WIT package with no
380 /// // dependencies.
381 /// bindgen!("foo" in "foo.wit");
382 /// ```
383 ///
384 /// A more configured version of invoking this macro looks like:
385 ///
386 /// ```rust,ignore
387 /// bindgen!({
388 ///     world: "foo", // not needed if `path` has one `world`
389 ///
390 ///     // same as in `bindgen!(in "other/wit/folder")
391 ///     path: "other/wit/folder",
392 ///
393 ///     // Instead of `path` the WIT document can be provided inline if
394 ///     // desired.
395 ///     inline: "
396 ///         package my:inline;
397 ///
398 ///         world foo {
399 ///             // ...
400 ///         }
401 ///     ",
402 ///
403 ///     // Add calls to `tracing::span!` before each import or export is called
404 ///     // to log arguments and return values.
405 ///     //
406 ///     // This option defaults to `false`.
407 ///     tracing: true,
408 ///
409 ///     // Imports will be async functions through #[async_trait] and exports
410 ///     // are also invoked as async functions. Requires `Config::async_support`
411 ///     // to be `true`.
412 ///     //
413 ///     // Note that this is only async for the host as the guest will still
414 ///     // appear as if it's invoking blocking functions.
415 ///     //
416 ///     // This option defaults to `false`.
417 ///     async: true,
418 ///
419 ///     // Alternative mode of async configuration where this still implies
420 ///     // async instantiation happens, for example, but more control is
421 ///     // provided over which imports are async and which aren't.
422 ///     //
423 ///     // Note that in this mode all exports are still async.
424 ///     async: {
425 ///         // All imports are async except for functions with these names
426 ///         except_imports: ["foo", "bar"],
427 ///
428 ///         // All imports are synchronous except for functions with these names
429 ///         //
430 ///         // Note that this key cannot be specified with `except_imports`,
431 ///         // only one or the other is accepted.
432 ///         only_imports: ["foo", "bar"],
433 ///     },
434 ///
435 ///     // This option is used to indicate whether imports can trap.
436 ///     //
437 ///     // Imports that may trap have their return types wrapped in
438 ///     // `wasmtime::Result<T>` where the `Err` variant indicates that a
439 ///     // trap will be raised in the guest.
440 ///     //
441 ///     // By default imports cannot trap and the return value is the return
442 ///     // value from the WIT bindings itself. This value can be set to `true`
443 ///     // to indicate that any import can trap. This value can also be set to
444 ///     // an array-of-strings to indicate that only a set list of imports
445 ///     // can trap.
446 ///     trappable_imports: false,             // no imports can trap (default)
447 ///     // trappable_imports: true,           // all imports can trap
448 ///     // trappable_imports: ["foo", "bar"], // only these can trap
449 ///
450 ///     // This can be used to translate WIT return values of the form
451 ///     // `result<T, error-type>` into `Result<T, RustErrorType>` in Rust.
452 ///     // Users must define `RustErrorType` and the `Host` trait for the
453 ///     // interface which defines `error-type` will have a method
454 ///     // called `convert_error_type` which converts `RustErrorType`
455 ///     // into `wasmtime::Result<ErrorType>`. This conversion can either
456 ///     // return the raw WIT error (`ErrorType` here) or a trap.
457 ///     //
458 ///     // By default this option is not specified. This option only takes
459 ///     // effect when `trappable_imports` is set for some imports.
460 ///     trappable_error_type: {
461 ///         "wasi:io/streams/stream-error" => RustErrorType,
462 ///     },
463 ///
464 ///     // All generated bindgen types are "owned" meaning types like `String`
465 ///     // are used instead of `&str`, for example. This is the default and
466 ///     // ensures that the same type used in both imports and exports uses the
467 ///     // same generated type.
468 ///     ownership: Owning,
469 ///
470 ///     // Alternative to `Owning` above where borrowed types attempt to be used
471 ///     // instead. The `duplicate_if_necessary` configures whether duplicate
472 ///     // Rust types will be generated for the same WIT type if necessary, for
473 ///     // example when a type is used both as an import and an export.
474 ///     ownership: Borrowing {
475 ///         duplicate_if_necessary: true
476 ///     },
477 ///
478 ///     // Restrict the code generated to what's needed for the interface
479 ///     // imports in the inlined WIT document fragment.
480 ///     interfaces: "
481 ///         import wasi:cli/command;
482 ///     ",
483 ///
484 ///     // Remap imported interfaces or resources to types defined in Rust
485 ///     // elsewhere. Using this option will prevent any code from being
486 ///     // generated for interfaces mentioned here. Resources named here will
487 ///     // not have a type generated to represent the resource.
488 ///     //
489 ///     // Interfaces mapped with this option should be previously generated
490 ///     // with an invocation of this macro. Resources need to be mapped to a
491 ///     // Rust type name.
492 ///     with: {
493 ///         // This can be used to indicate that entire interfaces have
494 ///         // bindings generated elsewhere with a path pointing to the
495 ///         // bindinges-generated module.
496 ///         "wasi:random/random": wasmtime_wasi::bindings::random::random,
497 ///
498 ///         // Similarly entire packages can also be specified.
499 ///         "wasi:cli": wasmtime_wasi::bindings::cli,
500 ///
501 ///         // Or, if applicable, entire namespaces can additionally be mapped.
502 ///         "wasi": wasmtime_wasi::bindings,
503 ///
504 ///         // Versions are supported if multiple versions are in play:
505 ///         "wasi:http/types@0.2.0": wasmtime_wasi_http::bindings::http::types,
506 ///         "wasi:[email protected]": wasmtime_wasi_http::bindings::http,
507 ///
508 ///         // The `with` key can also be used to specify the `T` used in
509 ///         // import bindings of `Resource<T>`. This can be done to configure
510 ///         // which typed resource shows up in generated bindings and can be
511 ///         // useful when working with the typed methods of `ResourceTable`.
512 ///         "wasi:filesystem/types/descriptor": MyDescriptorType,
513 ///     },
514 ///
515 ///     // Addtional derive attributes to include on generated types (structs or enums).
516 ///     //
517 ///     // These are deduplicated and attached in a deterministic order.
518 ///     additional_derives: [
519 ///         Hash,
520 ///         serde::Deserialize,
521 ///         serde::Serialize,
522 ///     ]
523 /// });
524 /// ```
525 pub use wasmtime_component_macro::bindgen;
526 
527 /// Derive macro to generate implementations of the [`ComponentType`] trait.
528 ///
529 /// This derive macro can be applied to `struct` and `enum` definitions and is
530 /// used to bind either a `record`, `enum`, or `variant` in the component model.
531 ///
532 /// Note you might be looking for [`bindgen!`] rather than this macro as that
533 /// will generate the entire type for you rather than just a trait
534 /// implementation.
535 ///
536 /// This macro supports a `#[component]` attribute which is used to customize
537 /// how the type is bound to the component model. A top-level `#[component]`
538 /// attribute is required to specify either `record`, `enum`, or `variant`.
539 ///
540 /// ## Records
541 ///
542 /// `record`s in the component model correspond to `struct`s in Rust. An example
543 /// is:
544 ///
545 /// ```rust
546 /// use wasmtime::component::ComponentType;
547 ///
548 /// #[derive(ComponentType)]
549 /// #[component(record)]
550 /// struct Color {
551 ///     r: u8,
552 ///     g: u8,
553 ///     b: u8,
554 /// }
555 /// ```
556 ///
557 /// which corresponds to the WIT type:
558 ///
559 /// ```wit
560 /// record color {
561 ///     r: u8,
562 ///     g: u8,
563 ///     b: u8,
564 /// }
565 /// ```
566 ///
567 /// Note that the name `Color` here does not need to match the name in WIT.
568 /// That's purely used as a name in Rust of what to refer to. The field names
569 /// must match that in WIT, however. Field names can be customized with the
570 /// `#[component]` attribute though.
571 ///
572 /// ```rust
573 /// use wasmtime::component::ComponentType;
574 ///
575 /// #[derive(ComponentType)]
576 /// #[component(record)]
577 /// struct VerboseColor {
578 ///     #[component(name = "r")]
579 ///     red: u8,
580 ///     #[component(name = "g")]
581 ///     green: u8,
582 ///     #[component(name = "b")]
583 ///     blue: u8,
584 /// }
585 /// ```
586 ///
587 /// Also note that field ordering is significant at this time and must match
588 /// WIT.
589 ///
590 /// ## Variants
591 ///
592 /// `variant`s in the component model correspond to a subset of shapes of a Rust
593 /// `enum`. Variants in the component model have a single optional payload type
594 /// which means that not all Rust `enum`s correspond to component model
595 /// `variant`s. An example variant is:
596 ///
597 /// ```rust
598 /// use wasmtime::component::ComponentType;
599 ///
600 /// #[derive(ComponentType)]
601 /// #[component(variant)]
602 /// enum Filter {
603 ///     #[component(name = "none")]
604 ///     None,
605 ///     #[component(name = "all")]
606 ///     All,
607 ///     #[component(name = "some")]
608 ///     Some(Vec<String>),
609 /// }
610 /// ```
611 ///
612 /// which corresponds to the WIT type:
613 ///
614 /// ```wit
615 /// variant filter {
616 ///     none,
617 ///     all,
618 ///     some(list<string>),
619 /// }
620 /// ```
621 ///
622 /// The `variant` style of derive allows an optional payload on Rust `enum`
623 /// variants but it must be a single unnamed field. Variants of the form `Foo(T,
624 /// U)` or `Foo { name: T }` are not supported at this time.
625 ///
626 /// Note that the order of variants in Rust must match the order of variants in
627 /// WIT. Additionally it's likely that `#[component(name = "...")]` is required
628 /// on all Rust `enum` variants because the name currently defaults to the Rust
629 /// name which is typically UpperCamelCase whereas WIT uses kebab-case.
630 ///
631 /// ## Enums
632 ///
633 /// `enum`s in the component model correspond to C-like `enum`s in Rust. Note
634 /// that a component model `enum` does not allow any payloads so the Rust `enum`
635 /// must additionally have no payloads.
636 ///
637 /// ```rust
638 /// use wasmtime::component::ComponentType;
639 ///
640 /// #[derive(ComponentType)]
641 /// #[component(enum)]
642 /// enum Setting {
643 ///     #[component(name = "yes")]
644 ///     Yes,
645 ///     #[component(name = "no")]
646 ///     No,
647 ///     #[component(name = "auto")]
648 ///     Auto,
649 /// }
650 /// ```
651 ///
652 /// which corresponds to the WIT type:
653 ///
654 /// ```wit
655 /// enum setting {
656 ///     yes,
657 ///     no,
658 ///     auto,
659 /// }
660 /// ```
661 ///
662 /// Note that the order of variants in Rust must match the order of variants in
663 /// WIT. Additionally it's likely that `#[component(name = "...")]` is required
664 /// on all Rust `enum` variants because the name currently defaults to the Rust
665 /// name which is typically UpperCamelCase whereas WIT uses kebab-case.
666 pub use wasmtime_component_macro::ComponentType;
667 
668 /// A derive macro for generating implementations of the [`Lift`] trait.
669 ///
670 /// This macro will likely be applied in conjunction with the
671 /// [`#[derive(ComponentType)]`](macro@ComponentType) macro along the lines
672 /// of `#[derive(ComponentType, Lift)]`. This trait enables reading values from
673 /// WebAssembly.
674 ///
675 /// Note you might be looking for [`bindgen!`] rather than this macro as that
676 /// will generate the entire type for you rather than just a trait
677 /// implementation.
678 ///
679 /// At this time this derive macro has no configuration.
680 ///
681 /// ## Examples
682 ///
683 /// ```rust
684 /// use wasmtime::component::{ComponentType, Lift};
685 ///
686 /// #[derive(ComponentType, Lift)]
687 /// #[component(record)]
688 /// struct Color {
689 ///     r: u8,
690 ///     g: u8,
691 ///     b: u8,
692 /// }
693 /// ```
694 pub use wasmtime_component_macro::Lift;
695 
696 /// A derive macro for generating implementations of the [`Lower`] trait.
697 ///
698 /// This macro will likely be applied in conjunction with the
699 /// [`#[derive(ComponentType)]`](macro@ComponentType) macro along the lines
700 /// of `#[derive(ComponentType, Lower)]`. This trait enables passing values to
701 /// WebAssembly.
702 ///
703 /// Note you might be looking for [`bindgen!`] rather than this macro as that
704 /// will generate the entire type for you rather than just a trait
705 /// implementation.
706 ///
707 /// At this time this derive macro has no configuration.
708 ///
709 /// ## Examples
710 ///
711 /// ```rust
712 /// use wasmtime::component::{ComponentType, Lower};
713 ///
714 /// #[derive(ComponentType, Lower)]
715 /// #[component(record)]
716 /// struct Color {
717 ///     r: u8,
718 ///     g: u8,
719 ///     b: u8,
720 /// }
721 /// ```
722 pub use wasmtime_component_macro::Lower;
723 
724 /// A macro to generate a Rust type corresponding to WIT `flags`
725 ///
726 /// This macro generates a type that implements the [`ComponentType`], [`Lift`],
727 /// and [`Lower`] traits. The generated Rust type corresponds to the `flags`
728 /// type in WIT.
729 ///
730 /// Example usage of this looks like:
731 ///
732 /// ```rust
733 /// use wasmtime::component::flags;
734 ///
735 /// flags! {
736 ///     Permissions {
737 ///         #[component(name = "read")]
738 ///         const READ;
739 ///         #[component(name = "write")]
740 ///         const WRITE;
741 ///         #[component(name = "execute")]
742 ///         const EXECUTE;
743 ///     }
744 /// }
745 ///
746 /// fn validate_permissions(permissions: &mut Permissions) {
747 ///     if permissions.contains(Permissions::EXECUTE | Permissions::WRITE) {
748 ///         panic!("cannot enable both writable and executable at the same time");
749 ///     }
750 ///
751 ///     if permissions.contains(Permissions::READ) {
752 ///         panic!("permissions must at least contain read");
753 ///     }
754 /// }
755 /// ```
756 ///
757 /// which corresponds to the WIT type:
758 ///
759 /// ```wit
760 /// flags permissions {
761 ///     read,
762 ///     write,
763 ///     execute,
764 /// }
765 /// ```
766 ///
767 /// This generates a structure which is similar to/inspired by the [`bitflags`
768 /// crate](https://crates.io/crates/bitflags). The `Permissions` structure
769 /// generated implements the [`PartialEq`], [`Eq`], [`Debug`], [`BitOr`],
770 /// [`BitOrAssign`], [`BitAnd`], [`BitAndAssign`], [`BitXor`], [`BitXorAssign`],
771 /// and [`Not`] traits - in addition to the Wasmtime-specific component ones
772 /// [`ComponentType`], [`Lift`], and [`Lower`].
773 ///
774 /// [`BitOr`]: std::ops::BitOr
775 /// [`BitOrAssign`]: std::ops::BitOrAssign
776 /// [`BitAnd`]: std::ops::BitAnd
777 /// [`BitAndAssign`]: std::ops::BitAndAssign
778 /// [`BitXor`]: std::ops::BitXor
779 /// [`BitXorAssign`]: std::ops::BitXorAssign
780 /// [`Not`]: std::ops::Not
781 pub use wasmtime_component_macro::flags;
782