Struct Binding 

pub struct Binding<PluginId, Ctx, Plugins = ExactlyOne<PluginId, PluginInstanceSync<Ctx>>, Instance = PluginInstanceSync<Ctx>>(/* private fields */)
where
    PluginId: Hash + Eq + Clone + Send + Sync + 'static,
    Ctx: PluginContext + 'static,
    Instance: Send + 'static,
    Plugins: Cardinality<PluginId, Instance> + 'static,
    <Plugins as Cardinality<PluginId, Instance>>::Rebind<Arc<Mutex<Instance>>>: Send + Sync;

An abstract contract specifying what plugins must implement (via plugs) or what they could depend on (via sockets). It bundles one or more WIT Interfaces under a single package name.

Binding is a handle to shared state. Cloning a Binding creates another handle to the same underlying binding, enabling shared dependencies where multiple plugins depend on the same binding.

let binding: Binding<String, Ctx> = Binding::new(
	"my:package",
	HashMap::from([
		( "api".to_string(), Interface::new(
			HashMap::from([( "get-value".into(), Function::new(
				FunctionKind::Freestanding,
				ReturnKind::MayContainResources,
			))]),
			HashSet::from([ "my-resource".to_string() ]),
		)),
	]),
	ExactlyOne( "my-plugin".to_string(), plugin ),
);

// Clone for shared dependencies - both refer to the same binding
let binding_clone = binding.clone();

Type Parameters

• PluginId: Unique identifier type for plugins (e.g., String, UUID)
• Ctx: Context stored in each plugin’s Wasmtime store
• Plugins: Cardinality wrapper containing the plugin instances
• Instance: PluginInstanceSync or PluginInstanceAsync

Implementations

impl<PluginId, Ctx, Plugins, Instance> Binding<PluginId, Ctx, Plugins, Instance>

where PluginId: Hash + Eq + Clone + Send + Sync + 'static, Ctx: PluginContext + 'static, Instance: Send + 'static, Plugins: Cardinality<PluginId, Instance> + 'static, <Plugins as Cardinality<PluginId, Instance>>::Rebind<Arc<Mutex<Instance>>>: Cardinality<PluginId, Arc<Mutex<Instance>>> + Send + Sync,

pub fn new( package_name: impl Into<String>, interfaces: HashMap<String, Interface>, plugins: Plugins, ) -> Self

Creates a new binding specification.

impl<PluginId, Ctx, Plugins> Binding<PluginId, Ctx, Plugins, PluginInstanceSync<Ctx>>

where PluginId: Hash + Eq + Clone + Send + Sync + 'static, Ctx: PluginContext + 'static, Plugins: Cardinality<PluginId, PluginInstanceSync<Ctx>> + 'static, <Plugins as Cardinality<PluginId, PluginInstanceSync<Ctx>>>::Rebind<Arc<Mutex<PluginInstanceSync<Ctx>>>>: Cardinality<PluginId, Arc<Mutex<PluginInstanceSync<Ctx>>>> + Send + Sync,

pub fn dispatch( &self, interface_name: &str, function_name: &str, args: &[Val], ) -> Result<<<Plugins as Cardinality<PluginId, PluginInstanceSync<Ctx>>>::Rebind<Arc<Mutex<PluginInstanceSync<Ctx>>>> as Cardinality<PluginId, Arc<Mutex<PluginInstanceSync<Ctx>>>>>::Rebind<Result<Val, DispatchError>>, DispatchError>

Dispatches a function call to all plugins implementing this binding.

This is used for external dispatch (calling into the plugin graph from outside). The result is wrapped in a type matching the binding’s cardinality.

Arguments

• interface_name - The interface name within this binding (e.g., “example”)
• function_name - The function name within the interface (e.g., “get-value”)
• args - Arguments to pass to the function

Returns

A cardinality wrapper containing Result<Val, DispatchError> for each plugin. For ReturnKind::Void, the value is an empty tuple (Val::Option( None )) placeholder.

Errors

Returns an error if the interface or function is not found in this binding.

impl<PluginId, Ctx, Plugins> Binding<PluginId, Ctx, Plugins, PluginInstanceAsync<Ctx>>

where PluginId: Hash + Eq + Clone + Send + Sync + 'static, Ctx: PluginContext + 'static, Plugins: Cardinality<PluginId, PluginInstanceAsync<Ctx>> + 'static, <Plugins as Cardinality<PluginId, PluginInstanceAsync<Ctx>>>::Rebind<Arc<Mutex<PluginInstanceAsync<Ctx>>>>: Cardinality<PluginId, Arc<Mutex<PluginInstanceAsync<Ctx>>>> + Send + Sync,

pub async fn dispatch_async( &self, interface_name: &str, function_name: &str, args: &[Val], ) -> Result<<<Plugins as Cardinality<PluginId, PluginInstanceAsync<Ctx>>>::Rebind<Arc<Mutex<PluginInstanceAsync<Ctx>>>> as Cardinality<PluginId, Arc<Mutex<PluginInstanceAsync<Ctx>>>>>::Rebind<Result<Val, DispatchError>>, DispatchError>

where PluginId: Into<Val>, <<Plugins as Cardinality<PluginId, PluginInstanceAsync<Ctx>>>::Rebind<Arc<Mutex<PluginInstanceAsync<Ctx>>>> as Cardinality<PluginId, Arc<Mutex<PluginInstanceAsync<Ctx>>>>>::Rebind<Result<Val, DispatchError>>: Send,

Asynchronously dispatches a function call to all plugins implementing this binding.

This method waits for a busy plugin instead of returning DispatchError::LockRejected. It is required for instances created by Plugin::instantiate_async or Plugin::link_async.

Example

let result = binding.dispatch_async( "root", "get", &[] ).await?;
assert!( matches!( result, ExactlyOne( _, Ok( Val::U32( 42 )))));

Errors

Returns an error if the interface or function is not found in this binding.

impl<PluginId, Ctx, Plugins, Instance> Binding<PluginId, Ctx, Plugins, Instance>

where PluginId: Hash + Eq + Clone + Send + Sync + 'static, Ctx: PluginContext + 'static, Instance: Send + 'static, Plugins: Cardinality<PluginId, Instance>, <Plugins as Cardinality<PluginId, Instance>>::Rebind<Arc<Mutex<Instance>>>: Send + Sync, BindingAny<PluginId, Ctx, Instance>: From<Binding<PluginId, Ctx, Plugins, Instance>>,

pub fn into_any(self) -> BindingAny<PluginId, Ctx, Instance>

Converts this binding into a type-erased BindingAny for heterogeneous socket lists.

Trait Implementations

impl<PluginId, Ctx, Plugins, Instance> Clone for Binding<PluginId, Ctx, Plugins, Instance>

where PluginId: Hash + Eq + Clone + Send + Sync + 'static, Ctx: PluginContext + 'static, Instance: Send + 'static, Plugins: Cardinality<PluginId, Instance> + 'static, <Plugins as Cardinality<PluginId, Instance>>::Rebind<Arc<Mutex<Instance>>>: Send + Sync,

fn clone(&self) -> Self

Creates another handle to the same underlying binding, enabling shared dependencies where multiple plugins depend on the same binding.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<PluginId, Ctx, Plugins, Instance> Debug for Binding<PluginId, Ctx, Plugins, Instance>

where PluginId: Hash + Eq + Clone + Send + Sync + Debug + 'static, Ctx: PluginContext + Debug + 'static, Instance: Send + 'static, Plugins: Cardinality<PluginId, Instance> + 'static, <Plugins as Cardinality<PluginId, Instance>>::Rebind<Arc<Mutex<Instance>>>: Send + Sync + Debug,

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<PluginId, Ctx, Instance> From<Binding<PluginId, Ctx, Any<PluginId, Instance>, Instance>> for BindingAny<PluginId, Ctx, Instance>

where PluginId: Hash + Eq + Clone + Send + Sync + 'static, Ctx: PluginContext + 'static, Instance: Send + 'static,

fn from( binding: Binding<PluginId, Ctx, Any<PluginId, Instance>, Instance>, ) -> Self

Converts to this type from the input type.

impl<PluginId, Ctx, Instance> From<Binding<PluginId, Ctx, AtLeastOne<PluginId, Instance>, Instance>> for BindingAny<PluginId, Ctx, Instance>

where PluginId: Hash + Eq + Clone + Send + Sync + 'static, Ctx: PluginContext + 'static, Instance: Send + 'static,

fn from( binding: Binding<PluginId, Ctx, AtLeastOne<PluginId, Instance>, Instance>, ) -> Self

Converts to this type from the input type.

impl<PluginId, Ctx, Instance> From<Binding<PluginId, Ctx, AtMostOne<PluginId, Instance>, Instance>> for BindingAny<PluginId, Ctx, Instance>

where PluginId: Hash + Eq + Clone + Send + Sync + 'static, Ctx: PluginContext + 'static, Instance: Send + 'static,

fn from( binding: Binding<PluginId, Ctx, AtMostOne<PluginId, Instance>, Instance>, ) -> Self

Converts to this type from the input type.

impl<PluginId, Ctx, Instance> From<Binding<PluginId, Ctx, ExactlyOne<PluginId, Instance>, Instance>> for BindingAny<PluginId, Ctx, Instance>

where PluginId: Hash + Eq + Clone + Send + Sync + 'static, Ctx: PluginContext + 'static, Instance: Send + 'static,

fn from( binding: Binding<PluginId, Ctx, ExactlyOne<PluginId, Instance>, Instance>, ) -> Self

Converts to this type from the input type.