Restore plugins code.

src/engine.rs

@@ -2019,6 +2019,7 @@ impl Engine {
                         )
                         .map_err(|err| err.new_position(*pos))
                     }
+                    Ok(f) if f.is_plugin_fn() => f.get_plugin_fn().call(args.as_mut(), *pos),
                     Ok(f) => {
                         f.get_native_fn()(self, args.as_mut()).map_err(|err| err.new_position(*pos))
                     }

src/fn_native.rs

@@ -1,6 +1,7 @@
 use crate::any::Dynamic;
 use crate::engine::Engine;
 use crate::parser::ScriptFnDef;
+use crate::plugin::PluginFunction;
 use crate::result::EvalAltResult;
 use crate::utils::ImmutableString;
 
@@ -96,6 +97,11 @@ pub type FnAny =
 /// A standard function that gets an iterator from a type.
 pub type IteratorFn = fn(Dynamic) -> Box<dyn Iterator<Item = Dynamic>>;
 
+#[cfg(feature = "sync")]
+pub type SharedPluginFunction = Arc<dyn PluginFunction + Send + Sync>;
+#[cfg(not(feature = "sync"))]
+pub type SharedPluginFunction = Rc<dyn PluginFunction>;
+
 /// A standard callback function.
 #[cfg(not(feature = "sync"))]
 pub type Callback<T, R> = Box<dyn Fn(&T) -> R + 'static>;
@@ -113,6 +119,8 @@ pub enum CallableFunction {
     Method(Shared<FnAny>),
     /// An iterator function.
     Iterator(IteratorFn),
+    /// A plugin-defined function,
+    Plugin(SharedPluginFunction),
     /// A script-defined function.
     Script(Shared<ScriptFnDef>),
 }
@@ -123,6 +131,7 @@ impl fmt::Debug for CallableFunction {
             Self::Pure(_) => write!(f, "NativePureFunction"),
             Self::Method(_) => write!(f, "NativeMethod"),
             Self::Iterator(_) => write!(f, "NativeIterator"),
+            Self::Plugin(_) => write!(f, "PluginFunction"),
             Self::Script(fn_def) => fmt::Debug::fmt(fn_def, f),
         }
     }
@@ -134,6 +143,7 @@ impl fmt::Display for CallableFunction {
             Self::Pure(_) => write!(f, "NativePureFunction"),
             Self::Method(_) => write!(f, "NativeMethod"),
             Self::Iterator(_) => write!(f, "NativeIterator"),
+            Self::Plugin(_) => write!(f, "PluginFunction"),
             CallableFunction::Script(s) => fmt::Display::fmt(s, f),
         }
     }
@@ -144,28 +154,35 @@ impl CallableFunction {
     pub fn is_pure(&self) -> bool {
         match self {
             Self::Pure(_) => true,
-            Self::Method(_) | Self::Iterator(_) | Self::Script(_) => false,
+            Self::Method(_) | Self::Iterator(_) | Self::Script(_) | Self::Plugin(_) => false,
         }
     }
     /// Is this a native Rust method function?
     pub fn is_method(&self) -> bool {
         match self {
             Self::Method(_) => true,
-            Self::Pure(_) | Self::Iterator(_) | Self::Script(_) => false,
+            Self::Pure(_) | Self::Iterator(_) | Self::Script(_) | Self::Plugin(_) => false,
         }
     }
     /// Is this an iterator function?
     pub fn is_iter(&self) -> bool {
         match self {
             Self::Iterator(_) => true,
-            Self::Pure(_) | Self::Method(_) | Self::Script(_) => false,
+            Self::Pure(_) | Self::Method(_) | Self::Script(_) | Self::Plugin(_) => false,
         }
     }
     /// Is this a Rhai-scripted function?
     pub fn is_script(&self) -> bool {
         match self {
             Self::Script(_) => true,
-            Self::Pure(_) | Self::Method(_) | Self::Iterator(_) => false,
+            Self::Pure(_) | Self::Method(_) | Self::Iterator(_) | Self::Plugin(_) => false,
+        }
+    }
+    /// Is this a plugin-defined function?
+    pub fn is_plugin_fn(&self) -> bool {
+        match self {
+            Self::Plugin(_) => true,
+            Self::Pure(_) | Self::Method(_) | Self::Iterator(_) | Self::Script(_) => false,
         }
     }
     /// Get a reference to a native Rust function.
@@ -176,7 +193,7 @@ impl CallableFunction {
     pub fn get_native_fn(&self) -> &FnAny {
         match self {
             Self::Pure(f) | Self::Method(f) => f.as_ref(),
-            Self::Iterator(_) | Self::Script(_) => unreachable!(),
+            Self::Iterator(_) | Self::Script(_) | Self::Plugin(_) => unreachable!(),
         }
     }
     /// Get a shared reference to a script-defined function definition.
@@ -186,7 +203,7 @@ impl CallableFunction {
     /// Panics if the `CallableFunction` is not `Script`.
     pub fn get_shared_fn_def(&self) -> Shared<ScriptFnDef> {
         match self {
-            Self::Pure(_) | Self::Method(_) | Self::Iterator(_) => unreachable!(),
+            Self::Pure(_) | Self::Method(_) | Self::Iterator(_) | Self::Plugin(_) => unreachable!(),
             Self::Script(f) => f.clone(),
         }
     }
@@ -197,7 +214,7 @@ impl CallableFunction {
     /// Panics if the `CallableFunction` is not `Script`.
     pub fn get_fn_def(&self) -> &ScriptFnDef {
         match self {
-            Self::Pure(_) | Self::Method(_) | Self::Iterator(_) => unreachable!(),
+            Self::Pure(_) | Self::Method(_) | Self::Iterator(_) | Self::Plugin(_) => unreachable!(),
             Self::Script(f) => f,
         }
     }
@@ -209,7 +226,18 @@ impl CallableFunction {
     pub fn get_iter_fn(&self) -> IteratorFn {
         match self {
             Self::Iterator(f) => *f,
-            Self::Pure(_) | Self::Method(_) | Self::Script(_) => unreachable!(),
+            Self::Pure(_) | Self::Method(_) | Self::Script(_) | Self::Plugin(_) => unreachable!(),
+        }
+    }
+    /// Get a reference to a plugin function.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the `CallableFunction` is not `Plugin`.
+    pub fn get_plugin_fn<'s>(&'s self) -> SharedPluginFunction {
+        match self {
+            Self::Plugin(f) => f.clone(),
+            Self::Pure(_) | Self::Method(_) | Self::Script(_) | Self::Iterator(_) => unreachable!(),
         }
     }
     /// Create a new `CallableFunction::Pure`.
@@ -220,6 +248,18 @@ impl CallableFunction {
     pub fn from_method(func: Box<FnAny>) -> Self {
         Self::Method(func.into())
     }
+
+    #[cfg(feature = "sync")]
+    /// Create a new `CallableFunction::Plugin`.
+    pub fn from_plugin(plugin: impl PluginFunction + 'static + Send + Sync) -> Self {
+        Self::Plugin(Arc::new(plugin))
+    }
+
+    #[cfg(not(feature = "sync"))]
+    /// Create a new `CallableFunction::Plugin`.
+    pub fn from_plugin(plugin: impl PluginFunction + 'static) -> Self {
+        Self::Plugin(Rc::new(plugin))
+    }
 }
 
 impl From<IteratorFn> for CallableFunction {

src/fn_register.rs

@@ -5,11 +5,91 @@ use crate::any::{Dynamic, Variant};
 use crate::engine::Engine;
 use crate::fn_native::{CallableFunction, FnAny, FnCallArgs, SendSync};
 use crate::parser::FnAccess;
+use crate::plugin::Plugin;
 use crate::result::EvalAltResult;
 use crate::utils::ImmutableString;
 
 use crate::stdlib::{any::TypeId, boxed::Box, mem};
 
+/// 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.
+pub trait RegisterPlugin<PL: crate::plugin::Plugin> {
+    /// Allow extensions of the engine's behavior.
+    ///
+    /// This can include importing modules, registering functions to the global name space, and
+    /// more.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use rhai::{FLOAT, INT, Module, ModuleResolver, RegisterFn, RegisterPlugin};
+    /// use rhai::plugin::*;
+    /// use rhai::module_resolvers::*;
+    ///
+    /// // A function we want to expose to Rhai.
+    /// #[derive(Copy, Clone)]
+    /// struct DistanceFunction();
+    ///
+    /// impl PluginFunction for DistanceFunction {
+    ///     fn is_method_call(&self) -> bool { false }
+    ///     fn is_varadic(&self) -> bool { false }
+    ///
+    ///     fn call(&self, args: &[&mut Dynamic], pos: Position) -> Result<Dynamic, Box<EvalAltResult>> {
+    ///         let x1: &FLOAT = args[0].downcast_ref::<FLOAT>().unwrap();
+    ///         let y1: &FLOAT = args[1].downcast_ref::<FLOAT>().unwrap();
+    ///         let x2: &FLOAT = args[2].downcast_ref::<FLOAT>().unwrap();
+    ///         let y2: &FLOAT = args[3].downcast_ref::<FLOAT>().unwrap();
+    ///         let square_sum = (y2 - y1).abs().powf(2.0) + (x2 -x1).abs().powf(2.0);
+    ///         Ok(Dynamic::from(square_sum.sqrt()))
+    ///     }
+    ///
+    ///     fn clone_boxed(&self) -> Box<dyn PluginFunction> {
+    ///         Box::new(DistanceFunction())
+    ///     }
+    /// }
+    ///
+    /// // A simple custom plugin. This should not usually be done with hand-written code.
+    /// #[derive(Copy, Clone)]
+    /// pub struct AdvancedMathPlugin();
+    ///
+    /// impl Plugin for AdvancedMathPlugin {
+    ///     fn register_contents(self, engine: &mut Engine) {
+    ///         // Plugins are allowed to have side-effects on the engine.
+    ///         engine.register_fn("get_mystic_number", || { 42 as FLOAT });
+    ///
+    ///         // Main purpose: create a module to expose the functions to Rhai.
+    ///         //
+    ///         // This is currently a hack. There needs to be a better API here for "plugin"
+    ///         // modules.
+    ///         let mut m = Module::new();
+    ///         m.set_fn("euclidean_distance".to_string(), FnAccess::Public,
+    ///                  &[std::any::TypeId::of::<FLOAT>(),
+    ///                    std::any::TypeId::of::<FLOAT>(),
+    ///                    std::any::TypeId::of::<FLOAT>(),
+    ///                    std::any::TypeId::of::<FLOAT>()],
+    ///                  CallableFunction::from_plugin(DistanceFunction()));
+    ///         let mut r = StaticModuleResolver::new();
+    ///         r.insert("Math::Advanced".to_string(), m);
+    ///         engine.set_module_resolver(Some(r));
+    ///     }
+    /// }
+    ///
+    ///
+    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
+    ///
+    /// let mut engine = Engine::new();
+    /// engine.register_plugin(AdvancedMathPlugin());
+    ///
+    /// assert_eq!(engine.eval::<FLOAT>(
+    ///     r#"import "Math::Advanced" as math;
+    ///        let x = math::euclidean_distance(0.0, 1.0, 0.0, get_mystic_number()); x"#)?, 41.0);
+    /// # Ok(())
+    /// # }
+    /// ```
+    fn register_plugin(&mut self, plugin: PL);
+}
+
 /// Trait to register custom functions with the `Engine`.
 pub trait RegisterFn<FN, ARGS, RET> {
     /// Register a custom function with the `Engine`.
@@ -111,6 +191,12 @@ pub fn by_value<T: Variant + Clone>(data: &mut Dynamic) -> T {
     }
 }
 
+impl<PL: Plugin> RegisterPlugin<PL> for Engine {
+    fn register_plugin(&mut self, plugin: PL) {
+        plugin.register_contents(self);
+    }
+}
+
 /// This macro creates a closure wrapping a registered function.
 macro_rules! make_func {
 	($fn:ident : $map:expr ; $($par:ident => $convert:expr),*) => {

src/lib.rs

@@ -84,6 +84,10 @@ mod module;
 mod optimize;
 pub mod packages;
 mod parser;
+#[cfg(not(feature = "no_module"))]
+pub mod plugin;
+#[cfg(feature = "no_module")]
+mod plugin;
 mod result;
 mod scope;
 mod stdlib;
@@ -95,7 +99,7 @@ pub use any::Dynamic;
 pub use engine::Engine;
 pub use error::{ParseError, ParseErrorType};
 pub use fn_native::IteratorFn;
-pub use fn_register::{RegisterFn, RegisterResultFn};
+pub use fn_register::{RegisterFn, RegisterPlugin, RegisterResultFn};
 pub use module::Module;
 pub use parser::{ImmutableString, AST, INT};
 pub use result::EvalAltResult;

src/module.rs

@@ -876,12 +876,10 @@ impl Module {
                 .functions
                 .iter()
                 .filter(|(_, (_, _, _, v))| match v {
-                    CallableFunction::Pure(_)
-                    | CallableFunction::Method(_)
-                    | CallableFunction::Iterator(_) => true,
                     CallableFunction::Script(ref f) => {
                         filter(f.access, f.name.as_str(), f.params.len())
                     }
+                    _ => true,
                 })
                 .map(|(&k, v)| (k, v.clone())),
         );
@@ -897,10 +895,8 @@ impl Module {
     /// Filter out the functions, retaining only some based on a filter predicate.
     pub(crate) fn retain_functions(&mut self, filter: impl Fn(FnAccess, &str, usize) -> bool) {
         self.functions.retain(|_, (_, _, _, v)| match v {
-            CallableFunction::Pure(_)
-            | CallableFunction::Method(_)
-            | CallableFunction::Iterator(_) => true,
             CallableFunction::Script(ref f) => filter(f.access, f.name.as_str(), f.params.len()),
+            _ => true,
         });
 
         self.all_functions.clear();

src/plugin.rs

@@ -0,0 +1,42 @@
+//! Module defining plugins in Rhai. Is exported for use by plugin authors.
+
+pub use crate::any::{Dynamic, Variant};
+pub use crate::fn_native::{CallableFunction, FnCallArgs, IteratorFn};
+pub use crate::parser::{
+    FnAccess,
+    FnAccess::{Private, Public},
+    AST,
+};
+pub use crate::result::EvalAltResult;
+pub use crate::scope::{Entry as ScopeEntry, EntryType as ScopeEntryType, Scope};
+pub use crate::token::{Position, Token};
+pub use crate::utils::StaticVec;
+pub use crate::Engine;
+
+#[cfg(features = "sync")]
+/// Represents an externally-written plugin for the Rhai interpreter.
+///
+/// This trait should not be used directly. Use the `#[plugin]` procedural attribute instead.
+pub trait Plugin: Send {
+    fn register_contents(self, engine: &mut Engine);
+}
+
+#[cfg(not(features = "sync"))]
+/// Represents an externally-written plugin for the Rhai interpreter.
+///
+/// This trait should not be used directly. Use the `#[plugin]` procedural attribute instead.
+pub trait Plugin: Send + Sync {
+    fn register_contents(self, engine: &mut Engine);
+}
+
+/// Represents a function that is statically defined within a plugin.
+///
+/// This trait should not be used directly. Use the `#[plugin]` procedural attribute instead.
+pub trait PluginFunction {
+    fn is_method_call(&self) -> bool;
+    fn is_varadic(&self) -> bool;
+
+    fn call(&self, args: &[&mut Dynamic], pos: Position) -> Result<Dynamic, Box<EvalAltResult>>;
+
+    fn clone_boxed(&self) -> Box<dyn PluginFunction>;
+}