rhai/src/api/register.rs

//! Module that defines the public function/module registration API of [`Engine`].

use crate::func::{FnCallArgs, RegisterNativeFunction, SendSync};
use crate::types::dynamic::Variant;
use crate::{
    Engine, EvalAltResult, FnAccess, FnNamespace, Identifier, Module, NativeCallContext, Shared,
};
use std::any::{type_name, TypeId};
#[cfg(feature = "no_std")]
use std::prelude::v1::*;

#[cfg(not(feature = "no_index"))]
use crate::Array;

#[cfg(not(feature = "no_object"))]
use crate::Map;

impl Engine {
    /// Get the global namespace module (which is the last module in `global_modules`).
    #[inline(always)]
    #[allow(dead_code)]
    pub(crate) fn global_namespace(&self) -> &Module {
        self.global_modules.first().expect("not empty")
    }
    /// Get a mutable reference to the global namespace module
    /// (which is the first module in `global_modules`).
    #[inline(always)]
    pub(crate) fn global_namespace_mut(&mut self) -> &mut Module {
        Shared::get_mut(self.global_modules.first_mut().expect("not empty")).expect("not shared")
    }
    /// Register a custom function with the [`Engine`].
    ///
    /// # Example
    ///
    /// ```
    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
    /// use rhai::Engine;
    ///
    /// // Normal function
    /// fn add(x: i64, y: i64) -> i64 {
    ///     x + y
    /// }
    ///
    /// let mut engine = Engine::new();
    ///
    /// engine.register_fn("add", add);
    ///
    /// assert_eq!(engine.eval::<i64>("add(40, 2)")?, 42);
    ///
    /// // You can also register a closure.
    /// engine.register_fn("sub", |x: i64, y: i64| x - y );
    ///
    /// assert_eq!(engine.eval::<i64>("sub(44, 2)")?, 42);
    /// # Ok(())
    /// # }
    /// ```
    #[inline]
    pub fn register_fn<N, A, F>(&mut self, name: N, func: F) -> &mut Self
    where
        N: AsRef<str> + Into<Identifier>,
        F: RegisterNativeFunction<A, ()>,
    {
        let param_types = F::param_types();

        #[cfg(feature = "metadata")]
        let mut param_type_names: crate::StaticVec<_> = F::param_names()
            .iter()
            .map(|ty| format!("_: {}", self.map_type_name(ty)))
            .collect();

        #[cfg(feature = "metadata")]
        if F::return_type() != TypeId::of::<()>() {
            param_type_names.push(self.map_type_name(F::return_type_name()).into());
        }

        #[cfg(feature = "metadata")]
        let param_type_names: Option<crate::StaticVec<_>> =
            Some(param_type_names.iter().map(|ty| ty.as_str()).collect());

        #[cfg(not(feature = "metadata"))]
        let param_type_names: Option<[&str; 0]> = None;

        self.global_namespace_mut().set_fn(
            name,
            FnNamespace::Global,
            FnAccess::Public,
            param_type_names.as_ref().map(|v| v.as_ref()),
            &param_types,
            func.into_callable_function(),
        );
        self
    }
    /// Register a custom fallible function with the [`Engine`].
    ///
    /// # Example
    ///
    /// ```
    /// use rhai::{Engine, EvalAltResult};
    ///
    /// // Normal function
    /// fn div(x: i64, y: i64) -> Result<i64, Box<EvalAltResult>> {
    ///     if y == 0 {
    ///         // '.into()' automatically converts to 'Box<EvalAltResult::ErrorRuntime>'
    ///         Err("division by zero!".into())
    ///     } else {
    ///         Ok(x / y)
    ///     }
    /// }
    ///
    /// let mut engine = Engine::new();
    ///
    /// engine.register_result_fn("div", div);
    ///
    /// engine.eval::<i64>("div(42, 0)")
    ///       .expect_err("expecting division by zero error!");
    /// ```
    #[inline]
    pub fn register_result_fn<N, A, F, R>(&mut self, name: N, func: F) -> &mut Self
    where
        N: AsRef<str> + Into<Identifier>,
        F: RegisterNativeFunction<A, Result<R, Box<EvalAltResult>>>,
    {
        let param_types = F::param_types();

        #[cfg(feature = "metadata")]
        let param_type_names: crate::StaticVec<_> = F::param_names()
            .iter()
            .map(|ty| format!("_: {}", self.map_type_name(ty)))
            .chain(std::iter::once(
                self.map_type_name(F::return_type_name()).into(),
            ))
            .collect();

        #[cfg(feature = "metadata")]
        let param_type_names: Option<crate::StaticVec<_>> =
            Some(param_type_names.iter().map(|ty| ty.as_str()).collect());

        #[cfg(not(feature = "metadata"))]
        let param_type_names: Option<[&str; 0]> = None;

        self.global_namespace_mut().set_fn(
            name,
            FnNamespace::Global,
            FnAccess::Public,
            param_type_names.as_ref().map(|v| v.as_ref()),
            &param_types,
            func.into_callable_function(),
        );
        self
    }
    /// Register a function of the [`Engine`].
    ///
    /// # WARNING - Low Level API
    ///
    /// This function is very low level.  It takes a list of [`TypeId`][std::any::TypeId]'s indicating the actual types of the parameters.
    ///
    /// ## Arguments
    ///
    /// Arguments are simply passed in as a mutable array of [`&mut Dynamic`][crate::Dynamic],
    /// The arguments are guaranteed to be of the correct types matching the [`TypeId`][std::any::TypeId]'s.
    ///
    /// To access a primary argument value (i.e. cloning is cheap), use: `args[n].as_xxx().unwrap()`
    ///
    /// To access an argument value and avoid cloning, use `std::mem::take(args[n]).cast::<T>()`.
    /// Notice that this will _consume_ the argument, replacing it with `()`.
    ///
    /// To access the first mutable parameter, use `args.get_mut(0).unwrap()`
    #[inline(always)]
    pub fn register_raw_fn<N, T>(
        &mut self,
        name: N,
        arg_types: &[TypeId],
        func: impl Fn(NativeCallContext, &mut FnCallArgs) -> Result<T, Box<EvalAltResult>>
            + SendSync
            + 'static,
    ) -> &mut Self
    where
        N: AsRef<str> + Into<Identifier>,
        T: Variant + Clone,
    {
        self.global_namespace_mut().set_raw_fn(
            name,
            FnNamespace::Global,
            FnAccess::Public,
            arg_types,
            func,
        );
        self
    }
    /// Register a custom type for use with the [`Engine`].
    /// The type must implement [`Clone`].
    ///
    /// # Example
    ///
    /// ```
    /// #[derive(Debug, Clone, Eq, PartialEq)]
    /// struct TestStruct {
    ///     field: i64
    /// }
    ///
    /// impl TestStruct {
    ///     fn new() -> Self { Self { field: 1 } }
    ///     fn update(&mut self, offset: i64) { self.field += offset; }
    /// }
    ///
    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
    /// use rhai::Engine;
    ///
    /// let mut engine = Engine::new();
    ///
    /// // Register API for the custom type.
    /// engine
    ///     .register_type::<TestStruct>()
    ///     .register_fn("new_ts", TestStruct::new)
    ///     // Use `register_fn` to register methods on the type.
    ///     .register_fn("update", TestStruct::update);
    ///
    /// # #[cfg(not(feature = "no_object"))]
    /// assert_eq!(
    ///     engine.eval::<TestStruct>("let x = new_ts(); x.update(41); x")?,
    ///     TestStruct { field: 42 }
    /// );
    /// # Ok(())
    /// # }
    /// ```
    #[inline(always)]
    pub fn register_type<T: Variant + Clone>(&mut self) -> &mut Self {
        self.register_type_with_name::<T>(type_name::<T>())
    }
    /// Register a custom type for use with the [`Engine`], with a pretty-print name
    /// for the `type_of` function. The type must implement [`Clone`].
    ///
    /// # Example
    ///
    /// ```
    /// #[derive(Clone)]
    /// struct TestStruct {
    ///     field: i64
    /// }
    ///
    /// impl TestStruct {
    ///     fn new() -> Self { Self { field: 1 } }
    /// }
    ///
    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
    /// use rhai::Engine;
    ///
    /// let mut engine = Engine::new();
    ///
    /// // Register API for the custom type.
    /// engine
    ///     .register_type::<TestStruct>()
    ///     .register_fn("new_ts", TestStruct::new);
    ///
    /// assert_eq!(
    ///     engine.eval::<String>("let x = new_ts(); type_of(x)")?,
    ///     "rust_out::TestStruct"
    /// );
    ///
    /// // Re-register the custom type with a name.
    /// engine.register_type_with_name::<TestStruct>("Hello");
    ///
    /// assert_eq!(
    ///     engine.eval::<String>("let x = new_ts(); type_of(x)")?,
    ///     "Hello"
    /// );
    /// # Ok(())
    /// # }
    /// ```
    #[inline(always)]
    pub fn register_type_with_name<T: Variant + Clone>(&mut self, name: &str) -> &mut Self {
        // Add the pretty-print type name into the map
        self.type_names
            .insert(type_name::<T>().into(), Box::new(name.into()));
        self
    }
    /// Register an type iterator for an iterable type with the [`Engine`].
    /// This is an advanced feature.
    #[inline(always)]
    pub fn register_iterator<T>(&mut self) -> &mut Self
    where
        T: Variant + Clone + IntoIterator,
        <T as IntoIterator>::Item: Variant + Clone,
    {
        self.global_namespace_mut().set_iterable::<T>();
        self
    }
    /// Register a getter function for a member of a registered type with the [`Engine`].
    ///
    /// The function signature must start with `&mut self` and not `&self`.
    ///
    /// Not available under `no_object`.
    ///
    /// # Example
    ///
    /// ```
    /// #[derive(Clone)]
    /// struct TestStruct {
    ///     field: i64
    /// }
    ///
    /// impl TestStruct {
    ///     fn new() -> Self { Self { field: 1 } }
    ///     // Even a getter must start with `&mut self` and not `&self`.
    ///     fn get_field(&mut self) -> i64  { self.field }
    /// }
    ///
    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
    /// use rhai::Engine;
    ///
    /// let mut engine = Engine::new();
    ///
    /// // Register API for the custom type.
    /// engine
    ///     .register_type::<TestStruct>()
    ///     .register_fn("new_ts", TestStruct::new)
    ///     // Register a getter on a property (notice it doesn't have to be the same name).
    ///     .register_get("xyz", TestStruct::get_field);
    ///
    /// assert_eq!(engine.eval::<i64>("let a = new_ts(); a.xyz")?, 1);
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(not(feature = "no_object"))]
    #[inline(always)]
    pub fn register_get<T: Variant + Clone, V: Variant + Clone>(
        &mut self,
        name: impl AsRef<str>,
        get_fn: impl Fn(&mut T) -> V + SendSync + 'static,
    ) -> &mut Self {
        self.register_fn(&crate::engine::make_getter(name), get_fn)
    }
    /// Register a getter function for a member of a registered type with the [`Engine`].
    ///
    /// The function signature must start with `&mut self` and not `&self`.
    ///
    /// Not available under `no_object`.
    ///
    /// # Example
    ///
    /// ```
    /// use rhai::{Engine, Dynamic, EvalAltResult};
    ///
    /// #[derive(Clone)]
    /// struct TestStruct {
    ///     field: i64
    /// }
    ///
    /// impl TestStruct {
    ///     fn new() -> Self { Self { field: 1 } }
    ///     // Even a getter must start with `&mut self` and not `&self`.
    ///     fn get_field(&mut self) -> Result<i64, Box<EvalAltResult>> {
    ///         Ok(self.field)
    ///     }
    /// }
    ///
    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
    /// let mut engine = Engine::new();
    ///
    /// // Register API for the custom type.
    /// engine
    ///     .register_type::<TestStruct>()
    ///     .register_fn("new_ts", TestStruct::new)
    ///     // Register a getter on a property (notice it doesn't have to be the same name).
    ///     .register_get_result("xyz", TestStruct::get_field);
    ///
    /// assert_eq!(engine.eval::<i64>("let a = new_ts(); a.xyz")?, 1);
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(not(feature = "no_object"))]
    #[inline(always)]
    pub fn register_get_result<T: Variant + Clone, V: Variant + Clone>(
        &mut self,
        name: impl AsRef<str>,
        get_fn: impl Fn(&mut T) -> Result<V, Box<EvalAltResult>> + SendSync + 'static,
    ) -> &mut Self {
        self.register_result_fn(&crate::engine::make_getter(name), get_fn)
    }
    /// Register a setter function for a member of a registered type with the [`Engine`].
    ///
    /// Not available under `no_object`.
    ///
    /// # Example
    ///
    /// ```
    /// #[derive(Debug, Clone, Eq, PartialEq)]
    /// struct TestStruct {
    ///     field: i64
    /// }
    ///
    /// impl TestStruct {
    ///     fn new() -> Self { Self { field: 1 } }
    ///     fn set_field(&mut self, new_val: i64) { self.field = new_val; }
    /// }
    ///
    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
    /// use rhai::Engine;
    ///
    /// let mut engine = Engine::new();
    ///
    /// // Register API for the custom type.
    /// engine
    ///     .register_type::<TestStruct>()
    ///     .register_fn("new_ts", TestStruct::new)
    ///     // Register a setter on a property (notice it doesn't have to be the same name)
    ///     .register_set("xyz", TestStruct::set_field);
    ///
    /// // Notice that, with a getter, there is no way to get the property value
    /// assert_eq!(
    ///     engine.eval::<TestStruct>("let a = new_ts(); a.xyz = 42; a")?,
    ///     TestStruct { field: 42 }
    /// );
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(not(feature = "no_object"))]
    #[inline(always)]
    pub fn register_set<T: Variant + Clone, V: Variant + Clone>(
        &mut self,
        name: impl AsRef<str>,
        set_fn: impl Fn(&mut T, V) + SendSync + 'static,
    ) -> &mut Self {
        self.register_fn(&crate::engine::make_setter(name), set_fn)
    }
    /// Register a setter function for a member of a registered type with the [`Engine`].
    ///
    /// Not available under `no_object`.
    ///
    /// # Example
    ///
    /// ```
    /// use rhai::{Engine, Dynamic, EvalAltResult};
    ///
    /// #[derive(Debug, Clone, Eq, PartialEq)]
    /// struct TestStruct {
    ///     field: i64
    /// }
    ///
    /// impl TestStruct {
    ///     fn new() -> Self { Self { field: 1 } }
    ///     fn set_field(&mut self, new_val: i64) -> Result<(), Box<EvalAltResult>> {
    ///         self.field = new_val;
    ///         Ok(())
    ///     }
    /// }
    ///
    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
    /// let mut engine = Engine::new();
    ///
    /// // Register API for the custom type.
    /// engine
    ///     .register_type::<TestStruct>()
    ///     .register_fn("new_ts", TestStruct::new)
    ///     // Register a setter on a property (notice it doesn't have to be the same name)
    ///     .register_set_result("xyz", TestStruct::set_field);
    ///
    /// // Notice that, with a getter, there is no way to get the property value
    /// assert_eq!(
    ///     engine.eval::<TestStruct>("let a = new_ts(); a.xyz = 42; a")?,
    ///     TestStruct { field: 42 }
    /// );
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(not(feature = "no_object"))]
    #[inline(always)]
    pub fn register_set_result<T: Variant + Clone, V: Variant + Clone>(
        &mut self,
        name: impl AsRef<str>,
        set_fn: impl Fn(&mut T, V) -> Result<(), Box<EvalAltResult>> + SendSync + 'static,
    ) -> &mut Self {
        self.register_result_fn(&crate::engine::make_setter(name), set_fn)
    }
    /// Short-hand for registering both getter and setter functions
    /// of a registered type with the [`Engine`].
    ///
    /// All function signatures must start with `&mut self` and not `&self`.
    ///
    /// Not available under `no_object`.
    ///
    /// # Example
    ///
    /// ```
    /// #[derive(Clone)]
    /// struct TestStruct {
    ///     field: i64
    /// }
    ///
    /// impl TestStruct {
    ///     fn new() -> Self { Self { field: 1 } }
    ///     // Even a getter must start with `&mut self` and not `&self`.
    ///     fn get_field(&mut self) -> i64 { self.field }
    ///     fn set_field(&mut self, new_val: i64) { self.field = new_val; }
    /// }
    ///
    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
    /// use rhai::Engine;
    ///
    /// let mut engine = Engine::new();
    ///
    /// // Register API for the custom type.
    /// engine
    ///     .register_type::<TestStruct>()
    ///     .register_fn("new_ts", TestStruct::new)
    ///     // Register both a getter and a setter on a property
    ///     // (notice it doesn't have to be the same name)
    ///     .register_get_set("xyz", TestStruct::get_field, TestStruct::set_field);
    ///
    /// assert_eq!(engine.eval::<i64>("let a = new_ts(); a.xyz = 42; a.xyz")?, 42);
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(not(feature = "no_object"))]
    #[inline(always)]
    pub fn register_get_set<T: Variant + Clone, V: Variant + Clone>(
        &mut self,
        name: impl AsRef<str>,
        get_fn: impl Fn(&mut T) -> V + SendSync + 'static,
        set_fn: impl Fn(&mut T, V) + SendSync + 'static,
    ) -> &mut Self {
        self.register_get(&name, get_fn).register_set(&name, set_fn)
    }
    /// Register an index getter for a custom type with the [`Engine`].
    ///
    /// The function signature must start with `&mut self` and not `&self`.
    ///
    /// Not available under both `no_index` and `no_object`.
    ///
    /// # Panics
    ///
    /// Panics if the type is [`Array`], [`Map`], [`String`],
    /// [`ImmutableString`][crate::ImmutableString], `&str` or [`INT`][crate::INT].
    /// Indexers for arrays, object maps, strings and integers cannot be registered.
    ///
    /// # Example
    ///
    /// ```
    /// #[derive(Clone)]
    /// struct TestStruct {
    ///     fields: Vec<i64>
    /// }
    ///
    /// impl TestStruct {
    ///     fn new() -> Self { Self { fields: vec![1, 2, 3, 4, 5] } }
    ///     // Even a getter must start with `&mut self` and not `&self`.
    ///     fn get_field(&mut self, index: i64) -> i64 { self.fields[index as usize] }
    /// }
    ///
    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
    /// use rhai::Engine;
    ///
    /// let mut engine = Engine::new();
    ///
    /// // Register API for the custom type.
    /// # #[cfg(not(feature = "no_object"))]
    /// engine.register_type::<TestStruct>();
    ///
    /// engine
    ///     .register_fn("new_ts", TestStruct::new)
    ///     // Register an indexer.
    ///     .register_indexer_get(TestStruct::get_field);
    ///
    /// # #[cfg(not(feature = "no_index"))]
    /// assert_eq!(engine.eval::<i64>("let a = new_ts(); a[2]")?, 3);
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
    #[inline]
    pub fn register_indexer_get<T: Variant + Clone, X: Variant + Clone, V: Variant + Clone>(
        &mut self,
        get_fn: impl Fn(&mut T, X) -> V + SendSync + 'static,
    ) -> &mut Self {
        #[cfg(not(feature = "no_index"))]
        if TypeId::of::<T>() == TypeId::of::<Array>() {
            panic!("Cannot register indexer for arrays.");
        }
        #[cfg(not(feature = "no_object"))]
        if TypeId::of::<T>() == TypeId::of::<Map>() {
            panic!("Cannot register indexer for object maps.");
        }
        if TypeId::of::<T>() == TypeId::of::<String>()
            || TypeId::of::<T>() == TypeId::of::<&str>()
            || TypeId::of::<T>() == TypeId::of::<crate::ImmutableString>()
        {
            panic!("Cannot register indexer for strings.");
        }
        if TypeId::of::<T>() == TypeId::of::<crate::INT>() {
            panic!("Cannot register indexer for integers.");
        }

        self.register_fn(crate::engine::FN_IDX_GET, get_fn)
    }
    /// Register an index getter for a custom type with the [`Engine`].
    ///
    /// The function signature must start with `&mut self` and not `&self`.
    ///
    /// Not available under both `no_index` and `no_object`.
    ///
    /// # Panics
    ///
    /// Panics if the type is [`Array`], [`Map`], [`String`],
    /// [`ImmutableString`][crate::ImmutableString], `&str` or [`INT`][crate::INT].
    /// Indexers for arrays, object maps, strings and integers cannot be registered.
    ///
    /// # Example
    ///
    /// ```
    /// use rhai::{Engine, Dynamic, EvalAltResult};
    ///
    /// #[derive(Clone)]
    /// struct TestStruct {
    ///     fields: Vec<i64>
    /// }
    ///
    /// impl TestStruct {
    ///     fn new() -> Self { Self { fields: vec![1, 2, 3, 4, 5] } }
    ///     // Even a getter must start with `&mut self` and not `&self`.
    ///     fn get_field(&mut self, index: i64) -> Result<i64, Box<EvalAltResult>> {
    ///         Ok(self.fields[index as usize])
    ///     }
    /// }
    ///
    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
    /// let mut engine = Engine::new();
    ///
    /// // Register API for the custom type.
    /// # #[cfg(not(feature = "no_object"))]
    /// engine.register_type::<TestStruct>();
    ///
    /// engine
    ///     .register_fn("new_ts", TestStruct::new)
    ///     // Register an indexer.
    ///     .register_indexer_get_result(TestStruct::get_field);
    ///
    /// # #[cfg(not(feature = "no_index"))]
    /// assert_eq!(engine.eval::<i64>("let a = new_ts(); a[2]")?, 3);
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
    #[inline]
    pub fn register_indexer_get_result<
        T: Variant + Clone,
        X: Variant + Clone,
        V: Variant + Clone,
    >(
        &mut self,
        get_fn: impl Fn(&mut T, X) -> Result<V, Box<EvalAltResult>> + SendSync + 'static,
    ) -> &mut Self {
        #[cfg(not(feature = "no_index"))]
        if TypeId::of::<T>() == TypeId::of::<Array>() {
            panic!("Cannot register indexer for arrays.");
        }
        #[cfg(not(feature = "no_object"))]
        if TypeId::of::<T>() == TypeId::of::<Map>() {
            panic!("Cannot register indexer for object maps.");
        }
        if TypeId::of::<T>() == TypeId::of::<String>()
            || TypeId::of::<T>() == TypeId::of::<&str>()
            || TypeId::of::<T>() == TypeId::of::<crate::ImmutableString>()
        {
            panic!("Cannot register indexer for strings.");
        }
        if TypeId::of::<T>() == TypeId::of::<crate::INT>() {
            panic!("Cannot register indexer for integers.");
        }

        self.register_result_fn(crate::engine::FN_IDX_GET, get_fn)
    }
    /// Register an index setter for a custom type with the [`Engine`].
    ///
    /// Not available under both `no_index` and `no_object`.
    ///
    /// # Panics
    ///
    /// Panics if the type is [`Array`], [`Map`], [`String`],
    /// [`ImmutableString`][crate::ImmutableString], `&str` or [`INT`][crate::INT].
    /// Indexers for arrays, object maps, strings and integers cannot be registered.
    ///
    /// # Example
    ///
    /// ```
    /// #[derive(Clone)]
    /// struct TestStruct {
    ///     fields: Vec<i64>
    /// }
    ///
    /// impl TestStruct {
    ///     fn new() -> Self { Self { fields: vec![1, 2, 3, 4, 5] } }
    ///     fn set_field(&mut self, index: i64, value: i64) { self.fields[index as usize] = value; }
    /// }
    ///
    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
    /// use rhai::Engine;
    ///
    /// let mut engine = Engine::new();
    ///
    /// // Register API for the custom type.
    /// # #[cfg(not(feature = "no_object"))]
    /// engine.register_type::<TestStruct>();
    ///
    /// engine
    ///     .register_fn("new_ts", TestStruct::new)
    ///     // Register an indexer.
    ///     .register_indexer_set(TestStruct::set_field);
    ///
    /// # #[cfg(not(feature = "no_index"))]
    /// assert_eq!(
    ///     engine.eval::<TestStruct>("let a = new_ts(); a[2] = 42; a")?.fields[2],
    ///     42
    /// );
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
    #[inline]
    pub fn register_indexer_set<T: Variant + Clone, X: Variant + Clone, V: Variant + Clone>(
        &mut self,
        set_fn: impl Fn(&mut T, X, V) + SendSync + 'static,
    ) -> &mut Self {
        #[cfg(not(feature = "no_index"))]
        if TypeId::of::<T>() == TypeId::of::<Array>() {
            panic!("Cannot register indexer for arrays.");
        }
        #[cfg(not(feature = "no_object"))]
        if TypeId::of::<T>() == TypeId::of::<Map>() {
            panic!("Cannot register indexer for object maps.");
        }
        if TypeId::of::<T>() == TypeId::of::<String>()
            || TypeId::of::<T>() == TypeId::of::<&str>()
            || TypeId::of::<T>() == TypeId::of::<crate::ImmutableString>()
        {
            panic!("Cannot register indexer for strings.");
        }
        if TypeId::of::<T>() == TypeId::of::<crate::INT>() {
            panic!("Cannot register indexer for integers.");
        }

        self.register_fn(crate::engine::FN_IDX_SET, set_fn)
    }
    /// Register an index setter for a custom type with the [`Engine`].
    ///
    /// Not available under both `no_index` and `no_object`.
    ///
    /// # Panics
    ///
    /// Panics if the type is [`Array`], [`Map`], [`String`],
    /// [`ImmutableString`][crate::ImmutableString], `&str` or [`INT`][crate::INT].
    /// Indexers for arrays, object maps, strings and integers cannot be registered.
    ///
    /// # Example
    ///
    /// ```
    /// use rhai::{Engine, Dynamic, EvalAltResult};
    ///
    /// #[derive(Clone)]
    /// struct TestStruct {
    ///     fields: Vec<i64>
    /// }
    ///
    /// impl TestStruct {
    ///     fn new() -> Self { Self { fields: vec![1, 2, 3, 4, 5] } }
    ///     fn set_field(&mut self, index: i64, value: i64) -> Result<(), Box<EvalAltResult>> {
    ///         self.fields[index as usize] = value;
    ///         Ok(())
    ///     }
    /// }
    ///
    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
    /// let mut engine = Engine::new();
    ///
    /// // Register API for the custom type.
    /// # #[cfg(not(feature = "no_object"))]
    /// engine.register_type::<TestStruct>();
    ///
    /// engine
    ///     .register_fn("new_ts", TestStruct::new)
    ///     // Register an indexer.
    ///     .register_indexer_set_result(TestStruct::set_field);
    ///
    /// # #[cfg(not(feature = "no_index"))]
    /// assert_eq!(
    ///     engine.eval::<TestStruct>("let a = new_ts(); a[2] = 42; a")?.fields[2],
    ///     42
    /// );
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
    #[inline]
    pub fn register_indexer_set_result<
        T: Variant + Clone,
        X: Variant + Clone,
        V: Variant + Clone,
    >(
        &mut self,
        set_fn: impl Fn(&mut T, X, V) -> Result<(), Box<EvalAltResult>> + SendSync + 'static,
    ) -> &mut Self {
        #[cfg(not(feature = "no_index"))]
        if TypeId::of::<T>() == TypeId::of::<Array>() {
            panic!("Cannot register indexer for arrays.");
        }
        #[cfg(not(feature = "no_object"))]
        if TypeId::of::<T>() == TypeId::of::<Map>() {
            panic!("Cannot register indexer for object maps.");
        }
        if TypeId::of::<T>() == TypeId::of::<String>()
            || TypeId::of::<T>() == TypeId::of::<&str>()
            || TypeId::of::<T>() == TypeId::of::<crate::ImmutableString>()
        {
            panic!("Cannot register indexer for strings.");
        }
        if TypeId::of::<T>() == TypeId::of::<crate::INT>() {
            panic!("Cannot register indexer for integers.");
        }

        self.register_result_fn(crate::engine::FN_IDX_SET, set_fn)
    }
    /// Short-hand for registering both index getter and setter functions for a custom type with the [`Engine`].
    ///
    /// Not available under both `no_index` and `no_object`.
    ///
    /// # Panics
    ///
    /// Panics if the type is [`Array`], [`Map`], [`String`],
    /// [`ImmutableString`][crate::ImmutableString], `&str` or [`INT`][crate::INT].
    /// Indexers for arrays, object maps, strings and integers cannot be registered.
    ///
    /// # Example
    ///
    /// ```
    /// #[derive(Clone)]
    /// struct TestStruct {
    ///     fields: Vec<i64>
    /// }
    ///
    /// impl TestStruct {
    ///     fn new() -> Self { Self { fields: vec![1, 2, 3, 4, 5] } }
    ///     // Even a getter must start with `&mut self` and not `&self`.
    ///     fn get_field(&mut self, index: i64) -> i64 { self.fields[index as usize] }
    ///     fn set_field(&mut self, index: i64, value: i64) { self.fields[index as usize] = value; }
    /// }
    ///
    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
    /// use rhai::Engine;
    ///
    /// let mut engine = Engine::new();
    ///
    /// // Register API for the custom type.
    /// # #[cfg(not(feature = "no_object"))]
    /// engine.register_type::<TestStruct>();
    ///
    /// engine
    ///     .register_fn("new_ts", TestStruct::new)
    ///     // Register an indexer.
    ///     .register_indexer_get_set(TestStruct::get_field, TestStruct::set_field);
    ///
    /// # #[cfg(not(feature = "no_index"))]
    /// assert_eq!(engine.eval::<i64>("let a = new_ts(); a[2] = 42; a[2]")?, 42);
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(any(not(feature = "no_index"), not(feature = "no_object")))]
    #[inline(always)]
    pub fn register_indexer_get_set<T: Variant + Clone, X: Variant + Clone, V: Variant + Clone>(
        &mut self,
        get_fn: impl Fn(&mut T, X) -> V + SendSync + 'static,
        set_fn: impl Fn(&mut T, X, V) + SendSync + 'static,
    ) -> &mut Self {
        self.register_indexer_get(get_fn)
            .register_indexer_set(set_fn)
    }
    /// Register a shared [`Module`] into the global namespace of [`Engine`].
    ///
    /// All functions and type iterators are automatically available to scripts without namespace
    /// qualifications.
    ///
    /// Sub-modules and variables are **ignored**.
    ///
    /// When searching for functions, modules loaded later are preferred. In other words, loaded
    /// modules are searched in reverse order.
    #[inline(always)]
    pub fn register_global_module(&mut self, module: Shared<Module>) -> &mut Self {
        // Insert the module into the front.
        // The first module is always the global namespace.
        self.global_modules.insert(1, module);
        self
    }
    /// Register a shared [`Module`] as a static module namespace with the [`Engine`].
    ///
    /// Functions marked [`FnNamespace::Global`] and type iterators are exposed to scripts without
    /// namespace qualifications.
    ///
    /// Not available under `no_module`.
    ///
    /// # Example
    ///
    /// ```
    /// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
    /// use rhai::{Engine, Shared, Module};
    ///
    /// let mut engine = Engine::new();
    ///
    /// // Create the module
    /// let mut module = Module::new();
    /// module.set_native_fn("calc", |x: i64| Ok(x + 1));
    ///
    /// let module: Shared<Module> = module.into();
    ///
    /// engine
    ///     // Register the module as a fixed sub-module
    ///     .register_static_module("foo::bar::baz", module.clone())
    ///     // Multiple registrations to the same partial path is also OK!
    ///     .register_static_module("foo::bar::hello", module.clone())
    ///     .register_static_module("CalcService", module);
    ///
    /// assert_eq!(engine.eval::<i64>("foo::bar::baz::calc(41)")?, 42);
    /// assert_eq!(engine.eval::<i64>("foo::bar::hello::calc(41)")?, 42);
    /// assert_eq!(engine.eval::<i64>("CalcService::calc(41)")?, 42);
    /// # Ok(())
    /// # }
    /// ```
    #[cfg(not(feature = "no_module"))]
    pub fn register_static_module(
        &mut self,
        name: impl AsRef<str> + Into<Identifier>,
        module: Shared<Module>,
    ) -> &mut Self {
        fn register_static_module_raw(
            root: &mut std::collections::BTreeMap<Identifier, Shared<Module>>,
            name: impl AsRef<str> + Into<Identifier>,
            module: Shared<Module>,
        ) {
            let separator = crate::tokenizer::Token::DoubleColon.syntax();

            if !name.as_ref().contains(separator.as_ref()) {
                if !module.is_indexed() {
                    // Index the module (making a clone copy if necessary) if it is not indexed
                    let mut module = crate::func::native::shared_take_or_clone(module);
                    module.build_index();
                    root.insert(name.into(), module.into());
                } else {
                    root.insert(name.into(), module);
                }
            } else {
                let mut iter = name.as_ref().splitn(2, separator.as_ref());
                let sub_module = iter.next().expect("contains separator").trim();
                let remainder = iter.next().expect("contains separator").trim();

                if !root.contains_key(sub_module) {
                    let mut m = Module::new();
                    register_static_module_raw(m.sub_modules_mut(), remainder, module);
                    m.build_index();
                    root.insert(sub_module.into(), m.into());
                } else {
                    let m = root.remove(sub_module).expect("contains sub-module");
                    let mut m = crate::func::native::shared_take_or_clone(m);
                    register_static_module_raw(m.sub_modules_mut(), remainder, module);
                    m.build_index();
                    root.insert(sub_module.into(), m.into());
                }
            }
        }

        register_static_module_raw(&mut self.global_sub_modules, name, module);
        self
    }
    /// _(metadata)_ Generate a list of all registered functions.
    /// Exported under the `metadata` feature only.
    ///
    /// Functions from the following sources are included, in order:
    /// 1) Functions registered into the global namespace
    /// 2) Functions in registered sub-modules
    /// 3) Functions in packages (optional)
    #[cfg(feature = "metadata")]
    #[inline]
    #[must_use]
    pub fn gen_fn_signatures(&self, include_packages: bool) -> Vec<String> {
        let mut signatures = Vec::with_capacity(64);

        signatures.extend(self.global_namespace().gen_fn_signatures());

        self.global_sub_modules.iter().for_each(|(name, m)| {
            signatures.extend(m.gen_fn_signatures().map(|f| format!("{}::{}", name, f)))
        });

        if include_packages {
            signatures.extend(
                self.global_modules
                    .iter()
                    .skip(1)
                    .flat_map(|m| m.gen_fn_signatures()),
            );
        }

        signatures
    }
}