Added basic Plugin trait and test

Cargo.toml

@@ -22,6 +22,7 @@ num-traits = { version = "0.2.11", default-features = false }
 [features]
 #default = ["no_stdlib", "no_function", "no_index", "no_object", "no_float", "only_i32", "unchecked", "no_optimize", "sync"]
 default = []
+plugins = []
 unchecked = []      # unchecked arithmetic
 no_index = []       # no arrays and indexing
 no_float = []       # no floating-point

src/fn_register.rs

@@ -9,6 +9,49 @@ use crate::token::Position;
 
 use crate::stdlib::{any::TypeId, boxed::Box, string::ToString};
 
+/// A trait to register custom plugins with the `Engine`.
+///
+/// A plugin consists of a number of functions. All functions will be registered with the engine.
+#[cfg(feature = "plugins")]
+pub trait RegisterPlugin<PL: Plugin> {
+    /// Register a custom function with the `Engine`.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use rhai::{Dynamic, Engine, INT, Plugin, RegisterDynamicFn, RegisterPlugin};
+    ///
+    /// // A simple custom plugin type. This should not usually be done with hand-written code.
+    /// struct AddOffsetPlugin(INT);
+    /// impl AddOffsetPlugin {
+    ///     fn add_offset(&self, x: INT) -> Dynamic {
+    ///         Dynamic::from(x + self.0)
+    ///     }
+    /// }
+    /// impl Plugin for AddOffsetPlugin {
+    ///     fn name(&self) -> &str {
+    ///         "My Plugin"
+    ///     }
+    ///     fn register_contents(self, engine: &mut Engine) {
+    ///         let add_offset_fn: Box<dyn Fn(INT) -> Dynamic> = {
+    ///             Box::new(move |x| self.add_offset(x))
+    ///         };
+    ///         engine.register_dynamic_fn("add_offset", add_offset_fn);
+    ///     }
+    /// }
+    ///
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
+    ///
+    /// let mut engine = Engine::new();
+    /// engine.register_plugin(AddOffsetPlugin(50));
+    ///
+    /// assert_eq!(engine.eval::<i64>("add_offset(42)")?, 92);
+    /// # Ok(())
+    /// # }
+    /// ```
+    fn register_plugin(&mut self, plugin: PL);
+}
+
 /// A trait to register custom functions with the `Engine`.
 pub trait RegisterFn<FN, ARGS, RET> {
     /// Register a custom function with the `Engine`.
@@ -98,6 +141,15 @@ pub trait RegisterResultFn<FN, ARGS, RET> {
     fn register_result_fn(&mut self, name: &str, f: FN);
 }
 
+/// Represents an externally-written plugin for the Rhai interpreter.
+///
+/// This should not be used directly. Use the `plugin_module!` macro instead.
+#[cfg(feature = "plugins")]
+pub trait Plugin {
+    fn register_contents(self, engine: &mut Engine);
+    fn name(&self) -> &str;
+}
+
 // These types are used to build a unique _marker_ tuple type for each combination
 // of function parameter types in order to make each trait implementation unique.
 // That is because stable Rust currently does not allow distinguishing implementations
@@ -127,6 +179,13 @@ pub fn cloned<T: Clone>(data: &mut T) -> T {
     data.clone()
 }
 
+#[cfg(feature = "plugins")]
+impl<PL: Plugin> RegisterPlugin<PL> for Engine {
+    fn register_plugin(&mut self, plugin: PL) {
+        plugin.register_contents(self)
+    }
+}
+
 /// This macro counts the number of arguments via recursion.
 macro_rules! count_args {
     () => { 0_usize };

src/lib.rs

@@ -89,6 +89,8 @@ pub use engine::{calc_fn_spec as calc_fn_hash, Engine};
 pub use error::{ParseError, ParseErrorType};
 pub use fn_call::FuncArgs;
 pub use fn_register::{RegisterDynamicFn, RegisterFn, RegisterResultFn};
+#[cfg(feature = "plugins")]
+pub use fn_register::{Plugin, RegisterPlugin};
 pub use parser::{AST, INT};
 pub use result::EvalAltResult;
 pub use scope::Scope;