Struct JsRuntime

pub struct JsRuntime { /* private fields */ }

A single execution context of JavaScript. Corresponds roughly to the “Web Worker” concept in the DOM.

The JsRuntime future completes when there is an error or when all pending ops have completed.

Use JsRuntimeForSnapshot to be able to create a snapshot.

Note: since V8 11.6, all runtimes must have a common parent thread that initalized the V8 platform. This can be done by calling JsRuntime::init_platform explicitly, or it will be done automatically on the calling thread when the first runtime is created.

Implementations

impl JsRuntime

pub fn init_platform( v8_platform: Option<SharedRef<Platform>>, import_assertions_enabled: bool, )

Explicitly initalizes the V8 platform using the passed platform. This should only be called once per process. Further calls will be silently ignored.

pub fn new(options: RuntimeOptions) -> JsRuntime

Only constructor, configuration is done through options. Panics if the runtime cannot be initialized.

pub fn try_new(options: RuntimeOptions) -> Result<JsRuntime, Error>

Only constructor, configuration is done through options. Returns an error if the runtime cannot be initialized.

pub fn op_state_from(isolate: &Isolate) -> Rc<RefCell<OpState>>

Returns the OpState associated with the passed Isolate.

pub fn op_metadata(&self, name: &str) -> Option<OpMetadata>

Returns the OpMetadata associated with the op name. Note this is linear with respect to the number of ops registered.

pub fn main_context(&self) -> Global<Context>

pub fn v8_isolate(&mut self) -> &mut OwnedIsolate

pub fn inspector(&mut self) -> Rc<RefCell<JsRuntimeInspector>>

pub fn wait_for_inspector_disconnect(&mut self)

pub fn runtime_activity_stats_factory(&self) -> RuntimeActivityStatsFactory

pub fn handle_scope(&mut self) -> HandleScope<'_>

pub fn eval<'s, T>( scope: &mut HandleScope<'s>, code: &str, ) -> Option<Local<'s, T>>

where Local<'s, T>: TryFrom<Local<'s, Value>, Error = DataError>,

pub fn op_state(&mut self) -> Rc<RefCell<OpState>>

Returns the runtime’s op state, which can be used to maintain ops and access resources between op calls.

pub fn op_names(&self) -> Vec<&'static str>

Returns the runtime’s op names, ordered by OpId.

pub fn execute_script( &mut self, name: &'static str, source_code: impl IntoModuleCodeString, ) -> Result<Global<Value>, Error>

Executes traditional, non-ECMAScript-module JavaScript code, This code executes in the global scope by default, and it is possible to maintain local JS state and invoke this method multiple times.

name can be a filepath or any other string, but it is required to be 7-bit ASCII, eg.

• “/some/file/path.js”
• “”
• “[native code]”

The same name value can be used for multiple executions.

The source may be any type that implements the internal [IntoModuleCodeString] trait, but it is highly recommended that embedders use the ascii_str! to generate the fastest version of strings for v8 to handle. If the strings are not static, you may also pass a String generated by the format! macro.

Error can usually be downcast to JsError.

pub fn call( &mut self, function: &Global<Function>, ) -> impl Future<Output = Result<Global<Value>, Error>>

Call a function and return a future resolving with the return value of the function. If the function returns a promise, the future will resolve only once the event loop resolves the underlying promise. If the future rejects, the future will resolve with the underlying error.

The event loop must be polled seperately for this future to resolve. If the event loop is not polled, the future will never make progress.

pub fn scoped_call( scope: &mut HandleScope<'_>, function: &Global<Function>, ) -> impl Future<Output = Result<Global<Value>, Error>>

Call a function and returns a future resolving with the return value of the function. If the function returns a promise, the future will resolve only once the event loop resolves the underlying promise. If the future rejects, the future will resolve with the underlying error.

The event loop must be polled seperately for this future to resolve. If the event loop is not polled, the future will never make progress.

pub fn call_with_args( &mut self, function: &Global<Function>, args: &[Global<Value>], ) -> impl Future<Output = Result<Global<Value>, Error>>

Call a function and returns a future resolving with the return value of the function. If the function returns a promise, the future will resolve only once the event loop resolves the underlying promise. If the future rejects, the future will resolve with the underlying error.

The event loop must be polled seperately for this future to resolve. If the event loop is not polled, the future will never make progress.

pub fn scoped_call_with_args( scope: &mut HandleScope<'_>, function: &Global<Function>, args: &[Global<Value>], ) -> impl Future<Output = Result<Global<Value>, Error>>

Call a function and returns a future resolving with the return value of the function. If the function returns a promise, the future will resolve only once the event loop resolves the underlying promise. If the future rejects, the future will resolve with the underlying error.

The event loop must be polled seperately for this future to resolve. If the event loop is not polled, the future will never make progress.

pub async fn call_and_await( &mut self, function: &Global<Function>, ) -> Result<Global<Value>, Error>

👎Deprecated: Use call

Call a function. If it returns a promise, run the event loop until that promise is settled. If the promise rejects or there is an uncaught error in the event loop, return Err(error). Or return Ok(<await returned>).

pub async fn call_with_args_and_await( &mut self, function: &Global<Function>, args: &[Global<Value>], ) -> Result<Global<Value>, Error>

👎Deprecated: Use call_with_args

Call a function with args. If it returns a promise, run the event loop until that promise is settled. If the promise rejects or there is an uncaught error in the event loop, return Err(error). Or return Ok(<await returned>).

pub fn get_module_namespace( &mut self, module_id: ModuleId, ) -> Result<Global<Object>, Error>

Returns the namespace object of a module.

This is only available after module evaluation has completed. This function panics if module has not been instantiated.

pub fn add_near_heap_limit_callback<C>(&mut self, cb: C)

where C: FnMut(usize, usize) -> usize + 'static,

Registers a callback on the isolate when the memory limits are approached. Use this to prevent V8 from crashing the process when reaching the limit.

Calls the closure with the current heap limit and the initial heap limit. The return value of the closure is set as the new limit.

pub fn remove_near_heap_limit_callback(&mut self, heap_limit: usize)

pub fn maybe_init_inspector(&mut self)

pub fn resolve( &mut self, promise: Global<Value>, ) -> impl Future<Output = Result<Global<Value>, Error>>

Waits for the given value to resolve while polling the event loop.

This future resolves when either the value is resolved or the event loop runs to completion.

pub fn scoped_resolve( scope: &mut HandleScope<'_>, promise: Global<Value>, ) -> impl Future<Output = Result<Global<Value>, Error>>

Waits for the given value to resolve while polling the event loop.

This future resolves when either the value is resolved or the event loop runs to completion.

pub async fn resolve_value( &mut self, global: Global<Value>, ) -> Result<Global<Value>, Error>

👎Deprecated: Use resolve

Waits for the given value to resolve while polling the event loop.

This future resolves when either the value is resolved or the event loop runs to completion.

pub async fn run_event_loop( &mut self, poll_options: PollEventLoopOptions, ) -> Result<(), Error>

Runs event loop to completion

This future resolves when:

• there are no more pending dynamic imports
• there are no more pending ops
• there are no more active inspector sessions (only if PollEventLoopOptions.wait_for_inspector is set to true)

pub async fn with_event_loop_promise<'fut, T, E>( &mut self, fut: impl Future<Output = Result<T, E>> + Unpin + 'fut, poll_options: PollEventLoopOptions, ) -> Result<T, AnyError>

where AnyError: From<E>,

A utility function that run provided future concurrently with the event loop.

If the event loop resolves while polling the future, it return an error with the text Promise resolution is still pending but the event loop has already resolved.

pub async fn with_event_loop_future<'fut, T, E>( &mut self, fut: impl Future<Output = Result<T, E>> + Unpin + 'fut, poll_options: PollEventLoopOptions, ) -> Result<T, AnyError>

where AnyError: From<E>,

A utility function that run provided future concurrently with the event loop.

If the event loop resolves while polling the future, it will continue to be polled, regardless of whether it returned an error or success.

Useful for interacting with local inspector session.

pub fn poll_event_loop( &mut self, cx: &mut Context<'_>, poll_options: PollEventLoopOptions, ) -> Poll<Result<(), Error>>

Runs a single tick of event loop

If PollEventLoopOptions.wait_for_inspector is set to true, the event loop will return Poll::Pending if there are active inspector sessions.

impl JsRuntime

pub fn mod_evaluate( &mut self, id: ModuleId, ) -> impl Future<Output = Result<(), Error>>

Evaluates an already instantiated ES module.

Returns a future that resolves when module promise resolves. Implementors must manually call JsRuntime::run_event_loop to drive module evaluation future.

Modules with top-level await are treated like promises, so a throw in the top-level block of a module is treated as an unhandled rejection. These rejections are provided to the unhandled promise rejection handler, which has the opportunity to pass them off to error-handling code. If those rejections are not handled (indicated by a false return from that unhandled promise rejection handler), then the runtime will terminate.

The future provided by mod_evaluate will only return errors in the case where the runtime is shutdown and no longer available to provide unhandled rejection information.

This function panics if module has not been instantiated.

pub async fn load_main_es_module_from_code( &mut self, specifier: &ModuleSpecifier, code: impl IntoModuleCodeString, ) -> Result<ModuleId, Error>

Asynchronously load specified module and all of its dependencies.

The module will be marked as “main”, and because of that “import.meta.main” will return true when checked inside that module.

The source may be any type that implements the internal [IntoModuleCodeString] trait, but it is highly recommended that embedders use the ascii_str! to generate the fastest version of strings for v8 to handle. If the strings are not static, you may also pass a String generated by the format! macro.

User must call JsRuntime::mod_evaluate with returned ModuleId manually after load is finished.

pub async fn load_main_es_module( &mut self, specifier: &ModuleSpecifier, ) -> Result<ModuleId, Error>

Asynchronously load specified module and all of its dependencies, retrieving the module from the supplied ModuleLoader.

The module will be marked as “main”, and because of that “import.meta.main” will return true when checked inside that module.

User must call JsRuntime::mod_evaluate with returned ModuleId manually after load is finished.

pub async fn load_side_es_module_from_code( &mut self, specifier: &ModuleSpecifier, code: impl IntoModuleCodeString, ) -> Result<ModuleId, Error>

Asynchronously load specified ES module and all of its dependencies from the provided source.

This method is meant to be used when loading some utility code that might be later imported by the main module (ie. an entry point module).

The source may be any type that implements the internal [IntoModuleCodeString] trait, but it is highly recommended that embedders use the ascii_str! to generate the fastest version of strings for v8 to handle. If the strings are not static, you may also pass a String generated by the format! macro.

User must call JsRuntime::mod_evaluate with returned ModuleId manually after load is finished.

pub async fn load_side_es_module( &mut self, specifier: &ModuleSpecifier, ) -> Result<ModuleId, Error>

Asynchronously load specified ES module and all of its dependencies, retrieving the module from the supplied ModuleLoader.

This method is meant to be used when loading some utility code that might be later imported by the main module (ie. an entry point module).

User must call JsRuntime::mod_evaluate with returned ModuleId manually after load is finished.

pub fn lazy_load_es_module_with_code( &mut self, specifier: impl IntoModuleName, code: impl IntoModuleCodeString, ) -> Result<Global<Value>, Error>

Load and evaluate an ES module provided the specifier and source code.

The module should not have Top-Level Await (that is, it should be possible to evaluate it synchronously).

It is caller’s responsibility to ensure that not duplicate specifiers are passed to this method.