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//! quick-js is a a Rust wrapper for [QuickJS](https://bellard.org/quickjs/), a new Javascript //! engine by Fabrice Bellard. //! //! It enables easy and straight-forward execution of modern Javascript from Rust. //! //! ## Limitations //! //! * Windows is not supported yet //! //! ## Quickstart: //! //! ```rust //! use quick_js::{Context, JsValue}; //! //! let context = Context::new().unwrap(); //! //! // Eval. //! //! let value = context.eval("1 + 2").unwrap(); //! assert_eq!(value, JsValue::Int(3)); //! //! let value = context.eval_as::<String>(" var x = 100 + 250; x.toString() ").unwrap(); //! assert_eq!(&value, "350"); //! //! // Callbacks. //! //! context.add_callback("myCallback", |a: i32, b: i32| a + b).unwrap(); //! //! context.eval(r#" //! // x will equal 30 //! var x = myCallback(10, 20); //! "#).unwrap(); //! ``` #![deny(missing_docs)] mod bindings; mod callback; pub mod console; mod droppable_value; mod value; #[cfg(test)] mod tests; use std::{convert::TryFrom, error, fmt}; pub use callback::{Arguments, Callback}; pub use value::*; /// Error on Javascript execution. #[derive(PartialEq, Debug)] pub enum ExecutionError { /// Code to be executed contained zero-bytes. InputWithZeroBytes, /// Value conversion failed. (either input arguments or result value). Conversion(ValueError), /// Internal error. Internal(String), /// JS Exception was thrown. Exception(JsValue), /// JS Runtime exceeded the memory limit. OutOfMemory, #[doc(hidden)] __NonExhaustive, } impl fmt::Display for ExecutionError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { use ExecutionError::*; match self { InputWithZeroBytes => write!(f, "Invalid script input: code contains zero byte (\\0)"), Conversion(e) => e.fmt(f), Internal(e) => write!(f, "Internal error: {}", e), Exception(e) => write!(f, "{:?}", e), OutOfMemory => write!(f, "Out of memory: runtime memory limit exceeded"), __NonExhaustive => unreachable!(), } } } impl error::Error for ExecutionError {} impl From<ValueError> for ExecutionError { fn from(v: ValueError) -> Self { ExecutionError::Conversion(v) } } /// Error on context creation. #[derive(Debug)] pub enum ContextError { /// Runtime could not be created. RuntimeCreationFailed, /// Context could not be created. ContextCreationFailed, /// Execution error while building. Execution(ExecutionError), #[doc(hidden)] __NonExhaustive, } impl fmt::Display for ContextError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { use ContextError::*; match self { RuntimeCreationFailed => write!(f, "Could not create runtime"), ContextCreationFailed => write!(f, "Could not create context"), Execution(e) => e.fmt(f), __NonExhaustive => unreachable!(), } } } impl error::Error for ContextError {} /// A builder for [Context](Context). /// /// Create with [Context::builder](Context::builder). pub struct ContextBuilder { memory_limit: Option<usize>, console_backend: Option<Box<dyn console::ConsoleBackend>>, } impl ContextBuilder { fn new() -> Self { Self { memory_limit: None, console_backend: None, } } /// Sets the memory limit of the Javascript runtime (in bytes). /// /// If the limit is exceeded, methods like `eval` will return /// a `Err(ExecutionError::Exception(JsValue::Null))` // TODO: investigate why we don't get a proper exception message here. pub fn memory_limit(self, max_bytes: usize) -> Self { let mut s = self; s.memory_limit = Some(max_bytes); s } /// Set a console handler that will proxy `console.{log,trace,debug,...}` /// calls. /// /// The given argument must implement the [console::ConsoleBackend] trait. /// /// A very simple logger could look like this: pub fn console<B>(mut self, backend: B) -> Self where B: console::ConsoleBackend, { self.console_backend = Some(Box::new(backend)); self } /// Finalize the builder and build a JS Context. pub fn build(self) -> Result<Context, ContextError> { let wrapper = bindings::ContextWrapper::new(self.memory_limit)?; if let Some(be) = self.console_backend { wrapper.set_console(be).map_err(ContextError::Execution)?; } Ok(Context::from_wrapper(wrapper)) } } /// Context is a wrapper around a QuickJS Javascript context. /// It is the primary way to interact with the runtime. /// /// For each `Context` instance a new instance of QuickJS /// runtime is created. It means that it is safe to use /// different contexts in different threads, but each /// `Context` instance must be used only from a single thread. pub struct Context { wrapper: bindings::ContextWrapper, } impl Context { fn from_wrapper(wrapper: bindings::ContextWrapper) -> Self { Self { wrapper } } /// Create a `ContextBuilder` that allows customization of JS Runtime settings. /// /// For details, see the methods on `ContextBuilder`. /// /// ```rust /// let _context = quick_js::Context::builder() /// .memory_limit(100_000) /// .build() /// .unwrap(); /// ``` pub fn builder() -> ContextBuilder { ContextBuilder::new() } /// Create a new Javascript context with default settings. pub fn new() -> Result<Self, ContextError> { let wrapper = bindings::ContextWrapper::new(None)?; Ok(Self::from_wrapper(wrapper)) } /// Reset the Javascript engine. /// /// All state and callbacks will be removed. pub fn reset(self) -> Result<Self, ContextError> { let wrapper = self.wrapper.reset()?; Ok(Self { wrapper }) } /// Evaluates Javascript code and returns the value of the final expression. /// /// **Promises**: /// If the evaluated code returns a Promise, the event loop /// will be executed until the promise is finished. The final value of /// the promise will be returned, or a `ExecutionError::Exception` if the /// promise failed. /// /// ```rust /// use quick_js::{Context, JsValue}; /// let context = Context::new().unwrap(); /// /// let value = context.eval(" 1 + 2 + 3 "); /// assert_eq!( /// value, /// Ok(JsValue::Int(6)), /// ); /// /// let value = context.eval(r#" /// function f() { return 55 * 3; } /// let y = f(); /// var x = y.toString() + "!" /// x /// "#); /// assert_eq!( /// value, /// Ok(JsValue::String("165!".to_string())), /// ); /// ``` pub fn eval(&self, code: &str) -> Result<JsValue, ExecutionError> { let value_raw = self.wrapper.eval(code)?; let value = value_raw.to_value()?; Ok(value) } /// Evaluates Javascript code and returns the value of the final expression /// as a Rust type. /// /// **Promises**: /// If the evaluated code returns a Promise, the event loop /// will be executed until the promise is finished. The final value of /// the promise will be returned, or a `ExecutionError::Exception` if the /// promise failed. /// /// ```rust /// use quick_js::{Context}; /// let context = Context::new().unwrap(); /// /// let res = context.eval_as::<bool>(" 100 > 10 "); /// assert_eq!( /// res, /// Ok(true), /// ); /// /// let value: i32 = context.eval_as(" 10 + 10 ").unwrap(); /// assert_eq!( /// value, /// 20, /// ); /// ``` pub fn eval_as<R>(&self, code: &str) -> Result<R, ExecutionError> where R: TryFrom<JsValue>, R::Error: Into<ValueError>, { let value_raw = self.wrapper.eval(code)?; let value = value_raw.to_value()?; let ret = R::try_from(value).map_err(|e| e.into())?; Ok(ret) } /// Set a global variable. /// /// ```rust /// use quick_js::{Context, JsValue}; /// let context = Context::new().unwrap(); /// /// context.set_global("someGlobalVariable", 42).unwrap(); /// let value = context.eval_as::<i32>("someGlobalVariable").unwrap(); /// assert_eq!( /// value, /// 42, /// ); /// ``` pub fn set_global<V>(&self, name: &str, value: V) -> Result<(), ExecutionError> where V: Into<JsValue>, { let global = self.wrapper.global()?; global.set_property(name, value.into())?; Ok(()) } /// Call a global function in the Javascript namespace. /// /// **Promises**: /// If the evaluated code returns a Promise, the event loop /// will be executed until the promise is finished. The final value of /// the promise will be returned, or a `ExecutionError::Exception` if the /// promise failed. /// /// ```rust /// use quick_js::{Context, JsValue}; /// let context = Context::new().unwrap(); /// /// let res = context.call_function("encodeURIComponent", vec!["a=b"]); /// assert_eq!( /// res, /// Ok(JsValue::String("a%3Db".to_string())), /// ); /// ``` pub fn call_function( &self, function_name: &str, args: impl IntoIterator<Item = impl Into<JsValue>>, ) -> Result<JsValue, ExecutionError> { let qargs = args .into_iter() .map(|arg| self.wrapper.serialize_value(arg.into())) .collect::<Result<Vec<_>, _>>()?; let global = self.wrapper.global()?; let func_obj = global.property(function_name)?; if !func_obj.is_object() { return Err(ExecutionError::Internal(format!( "Could not find function '{}' in global scope: does not exist, or not an object", function_name ))); } let value = self.wrapper.call_function(func_obj, qargs)?.to_value()?; Ok(value) } /// Add a global JS function that is backed by a Rust function or closure. /// /// The callback must satisfy several requirements: /// * accepts 0 - 5 arguments /// * each argument must be convertible from a JsValue /// * must return a value /// * the return value must either: /// - be convertible to JsValue /// - be a Result<T, E> where T is convertible to JsValue /// if Err(e) is returned, a Javascript exception will be raised /// /// ```rust /// use quick_js::{Context, JsValue}; /// let context = Context::new().unwrap(); /// /// // Register a closue as a callback under the "add" name. /// // The 'add' function can now be called from Javascript code. /// context.add_callback("add", |a: i32, b: i32| { a + b }).unwrap(); /// /// // Now we try out the 'add' function via eval. /// let output = context.eval_as::<i32>(" add( 3 , 4 ) ").unwrap(); /// assert_eq!( /// output, /// 7, /// ); /// ``` pub fn add_callback<F>( &self, name: &str, callback: impl Callback<F> + 'static, ) -> Result<(), ExecutionError> { self.wrapper.add_callback(name, callback) } }