Implement private modifier for functions.

README.md

@@ -268,6 +268,7 @@ let ast = engine.compile_file("hello_world.rhai".into())?;
 ### Calling Rhai functions from Rust
 
 Rhai also allows working _backwards_ from the other direction - i.e. calling a Rhai-scripted function from Rust via `call_fn`.
+Functions declared with `private` are hidden and cannot be called from Rust (see also [modules]).
 
 ```rust
 // Define functions in a script.
@@ -287,6 +288,11 @@ let ast = engine.compile(true,
         fn hello() {
             42
         }
+
+        // this one is private and cannot be called by 'call_fn'
+        private hidden() {
+            throw "you shouldn't see me!";
+        }
     ")?;
 
 // A custom scope can also contain any variables/constants available to the functions
@@ -300,11 +306,15 @@ let result: i64 = engine.call_fn(&mut scope, &ast, "hello", ( String::from("abc"
 //                                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 //                                                          put arguments in a tuple
 
-let result: i64 = engine.call_fn(&mut scope, &ast, "hello", (123_i64,) )?
+let result: i64 = engine.call_fn(&mut scope, &ast, "hello", (123_i64,) )?;
 //                                                          ^^^^^^^^^^ tuple of one
 
-let result: i64 = engine.call_fn(&mut scope, &ast, "hello", () )?
+let result: i64 = engine.call_fn(&mut scope, &ast, "hello", () )?;
 //                                                          ^^ unit = tuple of zero
+
+// The following call will return a function-not-found error because
+// 'hidden' is declared with 'private'.
+let result: () = engine.call_fn(&mut scope, &ast, "hidden", ())?;
 ```
 
 ### Creating Rust anonymous functions from Rhai script
@@ -2052,13 +2062,17 @@ Modules can be disabled via the [`no_module`] feature.
 A module is a single script (or pre-compiled `AST`) containing global variables and functions.
 The `export` statement, which can only be at global level, exposes selected variables as members of a module.
 Variables not exported are private and invisible to the outside.
+All functions are automatically exported, unless it is prefixed with `private`.
+Functions declared `private` are invisible to the outside.
 
-All functions are automatically exported. Everything exported from a module is **constant** (**read-only**).
+Everything exported from a module is **constant** (**read-only**).
 
 ```rust
 // This is a module script.
 
-fn inc(x) { x + 1 }         // function
+fn inc(x) { x + 1 }         // public function
+
+private fn foo() {}         // private function - invisible to outside
 
 let private = 123;          // variable not exported - invisible to outside
 let x = 42;                 // this will be exported below

src/api.rs

@@ -999,7 +999,7 @@ impl Engine {
         let pos = Position::none();
 
         let fn_def = fn_lib
-            .get_function_by_signature(name, args.len())
+            .get_function_by_signature(name, args.len(), true)
             .ok_or_else(|| Box::new(EvalAltResult::ErrorFunctionNotFound(name.to_string(), pos)))?;
 
         let state = State::new(fn_lib);

src/engine.rs

@@ -7,7 +7,7 @@ use crate::optimize::OptimizationLevel;
 use crate::packages::{
     CorePackage, Package, PackageLibrary, PackageStore, PackagesCollection, StandardPackage,
 };
-use crate::parser::{Expr, FnDef, ReturnType, Stmt, AST};
+use crate::parser::{Expr, FnAccess, FnDef, ReturnType, Stmt, AST};
 use crate::result::EvalAltResult;
 use crate::scope::{EntryType as ScopeEntryType, Scope};
 use crate::token::Position;
@@ -234,10 +234,22 @@ impl FunctionsLib {
         self.get(&hash).map(|fn_def| fn_def.as_ref())
     }
     /// Get a function definition from the `FunctionsLib`.
-    pub fn get_function_by_signature(&self, name: &str, params: usize) -> Option<&FnDef> {
+    pub fn get_function_by_signature(
+        &self,
+        name: &str,
+        params: usize,
+        public_only: bool,
+    ) -> Option<&FnDef> {
         // Qualifiers (none) + function name + placeholders (one for each parameter).
         let hash = calc_fn_hash(empty(), name, repeat(EMPTY_TYPE_ID()).take(params));
-        self.get_function(hash)
+        let fn_def = self.get_function(hash);
+
+        match fn_def.as_ref().map(|f| f.access) {
+            None => None,
+            Some(FnAccess::Private) if public_only => None,
+            Some(FnAccess::Private) => fn_def,
+            Some(FnAccess::Public) => fn_def,
+        }
     }
     /// Merge another `FunctionsLib` into this `FunctionsLib`.
     pub fn merge(&self, other: &Self) -> Self {

src/module.rs

@@ -4,7 +4,7 @@
 use crate::any::{Dynamic, Variant};
 use crate::calc_fn_hash;
 use crate::engine::{Engine, FnAny, FnCallArgs, FunctionsLib, NativeFunction, ScriptedFunction};
-use crate::parser::{FnDef, AST};
+use crate::parser::{FnAccess, FnDef, AST};
 use crate::result::EvalAltResult;
 use crate::scope::{Entry as ScopeEntry, EntryType as ScopeEntryType, Scope};
 use crate::token::{Position, Token};
@@ -57,7 +57,7 @@ pub struct Module {
     all_variables: HashMap<u64, Dynamic>,
 
     /// External Rust functions.
-    functions: HashMap<u64, (String, Vec<TypeId>, NativeFunction)>,
+    functions: HashMap<u64, (String, FnAccess, Vec<TypeId>, NativeFunction)>,
 
     /// Flattened collection of all external Rust functions, including those in sub-modules.
     all_functions: HashMap<u64, NativeFunction>,
@@ -260,15 +260,21 @@ impl Module {
     /// Set a Rust function into the module, returning a hash key.
     ///
     /// If there is an existing Rust function of the same hash, it is replaced.
-    pub fn set_fn(&mut self, fn_name: String, params: Vec<TypeId>, func: Box<FnAny>) -> u64 {
+    pub fn set_fn(
+        &mut self,
+        fn_name: String,
+        access: FnAccess,
+        params: Vec<TypeId>,
+        func: Box<FnAny>,
+    ) -> u64 {
         let hash = calc_fn_hash(empty(), &fn_name, params.iter().cloned());
 
         #[cfg(not(feature = "sync"))]
         self.functions
-            .insert(hash, (fn_name, params, Rc::new(func)));
+            .insert(hash, (fn_name, access, params, Rc::new(func)));
         #[cfg(feature = "sync")]
         self.functions
-            .insert(hash, (fn_name, params, Arc::new(func)));
+            .insert(hash, (fn_name, access, params, Arc::new(func)));
 
         hash
     }
@@ -283,7 +289,7 @@ impl Module {
     /// use rhai::Module;
     ///
     /// let mut module = Module::new();
-    /// let hash = module.set_fn_0("calc", || Ok(42_i64));
+    /// let hash = module.set_fn_0("calc", || Ok(42_i64), false);
     /// assert!(module.get_fn(hash).is_some());
     /// ```
     pub fn set_fn_0<K: Into<String>, T: Into<Dynamic>>(
@@ -291,6 +297,7 @@ impl Module {
         fn_name: K,
         #[cfg(not(feature = "sync"))] func: impl Fn() -> FuncReturn<T> + 'static,
         #[cfg(feature = "sync")] func: impl Fn() -> FuncReturn<T> + Send + Sync + 'static,
+        is_private: bool,
     ) -> u64 {
         let f = move |_: &mut FnCallArgs, pos| {
             func()
@@ -298,7 +305,12 @@ impl Module {
                 .map_err(|err| EvalAltResult::set_position(err, pos))
         };
         let arg_types = vec![];
-        self.set_fn(fn_name.into(), arg_types, Box::new(f))
+        let access = if is_private {
+            FnAccess::Private
+        } else {
+            FnAccess::Public
+        };
+        self.set_fn(fn_name.into(), access, arg_types, Box::new(f))
     }
 
     /// Set a Rust function taking one parameter into the module, returning a hash key.
@@ -311,7 +323,7 @@ impl Module {
     /// use rhai::Module;
     ///
     /// let mut module = Module::new();
-    /// let hash = module.set_fn_1("calc", |x: i64| Ok(x + 1));
+    /// let hash = module.set_fn_1("calc", |x: i64| Ok(x + 1), false);
     /// assert!(module.get_fn(hash).is_some());
     /// ```
     pub fn set_fn_1<K: Into<String>, A: Variant + Clone, T: Into<Dynamic>>(
@@ -319,6 +331,7 @@ impl Module {
         fn_name: K,
         #[cfg(not(feature = "sync"))] func: impl Fn(A) -> FuncReturn<T> + 'static,
         #[cfg(feature = "sync")] func: impl Fn(A) -> FuncReturn<T> + Send + Sync + 'static,
+        is_private: bool,
     ) -> u64 {
         let f = move |args: &mut FnCallArgs, pos| {
             func(mem::take(args[0]).cast::<A>())
@@ -326,7 +339,12 @@ impl Module {
                 .map_err(|err| EvalAltResult::set_position(err, pos))
         };
         let arg_types = vec![TypeId::of::<A>()];
-        self.set_fn(fn_name.into(), arg_types, Box::new(f))
+        let access = if is_private {
+            FnAccess::Private
+        } else {
+            FnAccess::Public
+        };
+        self.set_fn(fn_name.into(), access, arg_types, Box::new(f))
     }
 
     /// Set a Rust function taking one mutable parameter into the module, returning a hash key.
@@ -339,7 +357,7 @@ impl Module {
     /// use rhai::Module;
     ///
     /// let mut module = Module::new();
-    /// let hash = module.set_fn_1_mut("calc", |x: &mut i64| { *x += 1; Ok(*x) });
+    /// let hash = module.set_fn_1_mut("calc", |x: &mut i64| { *x += 1; Ok(*x) }, false);
     /// assert!(module.get_fn(hash).is_some());
     /// ```
     pub fn set_fn_1_mut<K: Into<String>, A: Variant + Clone, T: Into<Dynamic>>(
@@ -347,6 +365,7 @@ impl Module {
         fn_name: K,
         #[cfg(not(feature = "sync"))] func: impl Fn(&mut A) -> FuncReturn<T> + 'static,
         #[cfg(feature = "sync")] func: impl Fn(&mut A) -> FuncReturn<T> + Send + Sync + 'static,
+        is_private: bool,
     ) -> u64 {
         let f = move |args: &mut FnCallArgs, pos| {
             func(args[0].downcast_mut::<A>().unwrap())
@@ -354,7 +373,12 @@ impl Module {
                 .map_err(|err| EvalAltResult::set_position(err, pos))
         };
         let arg_types = vec![TypeId::of::<A>()];
-        self.set_fn(fn_name.into(), arg_types, Box::new(f))
+        let access = if is_private {
+            FnAccess::Private
+        } else {
+            FnAccess::Public
+        };
+        self.set_fn(fn_name.into(), access, arg_types, Box::new(f))
     }
 
     /// Set a Rust function taking two parameters into the module, returning a hash key.
@@ -369,7 +393,7 @@ impl Module {
     /// let mut module = Module::new();
     /// let hash = module.set_fn_2("calc", |x: i64, y: String| {
     ///     Ok(x + y.len() as i64)
-    /// });
+    /// }, false);
     /// assert!(module.get_fn(hash).is_some());
     /// ```
     pub fn set_fn_2<K: Into<String>, A: Variant + Clone, B: Variant + Clone, T: Into<Dynamic>>(
@@ -377,6 +401,7 @@ impl Module {
         fn_name: K,
         #[cfg(not(feature = "sync"))] func: impl Fn(A, B) -> FuncReturn<T> + 'static,
         #[cfg(feature = "sync")] func: impl Fn(A, B) -> FuncReturn<T> + Send + Sync + 'static,
+        is_private: bool,
     ) -> u64 {
         let f = move |args: &mut FnCallArgs, pos| {
             let a = mem::take(args[0]).cast::<A>();
@@ -387,7 +412,12 @@ impl Module {
                 .map_err(|err| EvalAltResult::set_position(err, pos))
         };
         let arg_types = vec![TypeId::of::<A>(), TypeId::of::<B>()];
-        self.set_fn(fn_name.into(), arg_types, Box::new(f))
+        let access = if is_private {
+            FnAccess::Private
+        } else {
+            FnAccess::Public
+        };
+        self.set_fn(fn_name.into(), access, arg_types, Box::new(f))
     }
 
     /// Set a Rust function taking two parameters (the first one mutable) into the module,
@@ -401,7 +431,7 @@ impl Module {
     /// let mut module = Module::new();
     /// let hash = module.set_fn_2_mut("calc", |x: &mut i64, y: String| {
     ///     *x += y.len() as i64; Ok(*x)
-    /// });
+    /// }, false);
     /// assert!(module.get_fn(hash).is_some());
     /// ```
     pub fn set_fn_2_mut<
@@ -414,6 +444,7 @@ impl Module {
         fn_name: K,
         #[cfg(not(feature = "sync"))] func: impl Fn(&mut A, B) -> FuncReturn<T> + 'static,
         #[cfg(feature = "sync")] func: impl Fn(&mut A, B) -> FuncReturn<T> + Send + Sync + 'static,
+        is_private: bool,
     ) -> u64 {
         let f = move |args: &mut FnCallArgs, pos| {
             let b = mem::take(args[1]).cast::<B>();
@@ -424,7 +455,12 @@ impl Module {
                 .map_err(|err| EvalAltResult::set_position(err, pos))
         };
         let arg_types = vec![TypeId::of::<A>(), TypeId::of::<B>()];
-        self.set_fn(fn_name.into(), arg_types, Box::new(f))
+        let access = if is_private {
+            FnAccess::Private
+        } else {
+            FnAccess::Public
+        };
+        self.set_fn(fn_name.into(), access, arg_types, Box::new(f))
     }
 
     /// Set a Rust function taking three parameters into the module, returning a hash key.
@@ -439,7 +475,7 @@ impl Module {
     /// let mut module = Module::new();
     /// let hash = module.set_fn_3("calc", |x: i64, y: String, z: i64| {
     ///     Ok(x + y.len() as i64 + z)
-    /// });
+    /// }, false);
     /// assert!(module.get_fn(hash).is_some());
     /// ```
     pub fn set_fn_3<
@@ -453,6 +489,7 @@ impl Module {
         fn_name: K,
         #[cfg(not(feature = "sync"))] func: impl Fn(A, B, C) -> FuncReturn<T> + 'static,
         #[cfg(feature = "sync")] func: impl Fn(A, B, C) -> FuncReturn<T> + Send + Sync + 'static,
+        is_private: bool,
     ) -> u64 {
         let f = move |args: &mut FnCallArgs, pos| {
             let a = mem::take(args[0]).cast::<A>();
@@ -464,7 +501,12 @@ impl Module {
                 .map_err(|err| EvalAltResult::set_position(err, pos))
         };
         let arg_types = vec![TypeId::of::<A>(), TypeId::of::<B>(), TypeId::of::<C>()];
-        self.set_fn(fn_name.into(), arg_types, Box::new(f))
+        let access = if is_private {
+            FnAccess::Private
+        } else {
+            FnAccess::Public
+        };
+        self.set_fn(fn_name.into(), access, arg_types, Box::new(f))
     }
 
     /// Set a Rust function taking three parameters (the first one mutable) into the module,
@@ -480,7 +522,7 @@ impl Module {
     /// let mut module = Module::new();
     /// let hash = module.set_fn_3_mut("calc", |x: &mut i64, y: String, z: i64| {
     ///     *x += y.len() as i64 + z; Ok(*x)
-    /// });
+    /// }, false);
     /// assert!(module.get_fn(hash).is_some());
     /// ```
     pub fn set_fn_3_mut<
@@ -494,6 +536,7 @@ impl Module {
         fn_name: K,
         #[cfg(not(feature = "sync"))] func: impl Fn(&mut A, B, C) -> FuncReturn<T> + 'static,
         #[cfg(feature = "sync")] func: impl Fn(&mut A, B, C) -> FuncReturn<T> + Send + Sync + 'static,
+        is_private: bool,
     ) -> u64 {
         let f = move |args: &mut FnCallArgs, pos| {
             let b = mem::take(args[1]).cast::<B>();
@@ -505,7 +548,12 @@ impl Module {
                 .map_err(|err| EvalAltResult::set_position(err, pos))
         };
         let arg_types = vec![TypeId::of::<A>(), TypeId::of::<B>(), TypeId::of::<C>()];
-        self.set_fn(fn_name.into(), arg_types, Box::new(f))
+        let access = if is_private {
+            FnAccess::Private
+        } else {
+            FnAccess::Public
+        };
+        self.set_fn(fn_name.into(), access, arg_types, Box::new(f))
     }
 
     /// Get a Rust function.
@@ -523,7 +571,7 @@ impl Module {
     /// assert!(module.get_fn(hash).is_some());
     /// ```
     pub fn get_fn(&self, hash: u64) -> Option<&Box<FnAny>> {
-        self.functions.get(&hash).map(|(_, _, v)| v.as_ref())
+        self.functions.get(&hash).map(|(_, _, _, v)| v.as_ref())
     }
 
     /// Get a modules-qualified function.
@@ -588,11 +636,7 @@ impl Module {
 
         scope.into_iter().for_each(
             |ScopeEntry {
-                 name,
+                 typ, value, alias, ..
-                 typ,
-                 value,
-                 alias,
-                 ..
              }| {
                 match typ {
                     // Variables with an alias left in the scope become module variables
@@ -641,7 +685,12 @@ impl Module {
                 variables.push((hash, value.clone()));
             }
             // Index all Rust functions
-            for (fn_name, params, func) in module.functions.values() {
+            for (fn_name, access, params, func) in module.functions.values() {
+                match access {
+                    // Private functions are not exported
+                    FnAccess::Private => continue,
+                    FnAccess::Public => (),
+                }
                 // Rust functions are indexed in two steps:
                 // 1) Calculate a hash in a similar manner to script-defined functions,
                 //    i.e. qualifiers + function name + dummy parameter types (one for each parameter).
@@ -660,6 +709,11 @@ impl Module {
             }
             // Index all script-defined functions
             for fn_def in module.fn_lib.values() {
+                match fn_def.access {
+                    // Private functions are not exported
+                    FnAccess::Private => continue,
+                    FnAccess::Public => (),
+                }
                 // Qualifiers + function name + placeholders (one for each parameter)
                 let hash = calc_fn_hash(
                     qualifiers.iter().map(|v| *v),

src/parser.rs

@@ -178,11 +178,22 @@ impl Add<Self> for &AST {
     }
 }
 
-/// A script-function definition.
+/// A type representing the access mode of a scripted function.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum FnAccess {
+    /// Private function.
+    Private,
+    /// Public function.
+    Public,
+}
+
+/// A scripted function definition.
 #[derive(Debug, Clone)]
 pub struct FnDef {
     /// Function name.
     pub name: String,
+    /// Function access mode.
+    pub access: FnAccess,
     /// Names of function parameters.
     pub params: Vec<String>,
     /// Function body.
@@ -2208,6 +2219,7 @@ fn parse_stmt<'a>(
 fn parse_fn<'a>(
     input: &mut Peekable<TokenIterator<'a>>,
     stack: &mut Stack,
+    access: FnAccess,
     allow_stmt_expr: bool,
 ) -> Result<FnDef, Box<ParseError>> {
     let pos = eat_token(input, Token::Fn);
@@ -2283,6 +2295,7 @@ fn parse_fn<'a>(
 
     Ok(FnDef {
         name,
+        access,
         params,
         body,
         pos,
@@ -2330,9 +2343,18 @@ fn parse_global_level<'a>(
         // Collect all the function definitions
         #[cfg(not(feature = "no_function"))]
         {
-            if let (Token::Fn, _) = input.peek().unwrap() {
+            let mut access = FnAccess::Public;
+            let mut must_be_fn = false;
+
+            if match_token(input, Token::Private)? {
+                access = FnAccess::Private;
+                must_be_fn = true;
+            }
+
+            match input.peek().unwrap() {
+                (Token::Fn, _) => {
                     let mut stack = Stack::new();
-                let func = parse_fn(input, &mut stack, true)?;
+                    let func = parse_fn(input, &mut stack, access, true)?;
 
                     // Qualifiers (none) + function name + argument `TypeId`'s
                     let hash = calc_fn_hash(
@@ -2344,6 +2366,15 @@ fn parse_global_level<'a>(
                     functions.insert(hash, func);
                     continue;
                 }
+                (_, pos) if must_be_fn => {
+                    return Err(PERR::MissingToken(
+                        Token::Fn.into(),
+                        format!("following '{}'", Token::Private.syntax()),
+                    )
+                    .into_err(*pos))
+                }
+                _ => (),
+            }
         }
         // Actual statement
         let stmt = parse_stmt(input, &mut stack, false, true, true)?;

src/token.rs

@@ -196,6 +196,7 @@ pub enum Token {
     XOrAssign,
     ModuloAssign,
     PowerOfAssign,
+    Private,
     Import,
     Export,
     As,
@@ -279,6 +280,7 @@ impl Token {
                 ModuloAssign => "%=",
                 PowerOf => "~",
                 PowerOfAssign => "~=",
+                Private => "private",
                 Import => "import",
                 Export => "export",
                 As => "as",
@@ -750,6 +752,7 @@ impl<'a> TokenIterator<'a> {
                             "throw" => Token::Throw,
                             "for" => Token::For,
                             "in" => Token::In,
+                            "private" => Token::Private,
 
                             #[cfg(not(feature = "no_module"))]
                             "import" => Token::Import,

tests/modules.rs

@@ -18,7 +18,12 @@ fn test_module_sub_module() -> Result<(), Box<EvalAltResult>> {
 
     let mut sub_module2 = Module::new();
     sub_module2.set_var("answer", 41 as INT);
-    let hash = sub_module2.set_fn_1("inc", |x: INT| Ok(x + 1));
+    let hash_inc = sub_module2.set_fn_1("inc", |x: INT| Ok(x + 1), false);
+    let hash_hidden = sub_module2.set_fn_0(
+        "hidden",
+        || Err("shouldn't see me!".into()) as Result<(), Box<EvalAltResult>>,
+        true,
+    );
 
     sub_module.set_sub_module("universe", sub_module2);
     module.set_sub_module("life", sub_module);
@@ -30,11 +35,12 @@ fn test_module_sub_module() -> Result<(), Box<EvalAltResult>> {
     let m2 = m.get_sub_module("universe").unwrap();
 
     assert!(m2.contains_var("answer"));
-    assert!(m2.contains_fn(hash));
+    assert!(m2.contains_fn(hash_inc));
+    assert!(m2.contains_fn(hash_hidden));
 
     assert_eq!(m2.get_var_value::<INT>("answer").unwrap(), 41);
 
-    let mut engine = Engine::new();
+    let engine = Engine::new();
     let mut scope = Scope::new();
 
     scope.push_module("question", module);
@@ -53,6 +59,11 @@ fn test_module_sub_module() -> Result<(), Box<EvalAltResult>> {
         )?,
         42
     );
+    assert!(matches!(
+        *engine.eval_expression_with_scope::<()>(&mut scope, "question::life::universe::hidden()")
+            .expect_err("should error"),
+        EvalAltResult::ErrorFunctionNotFound(fn_name, _) if fn_name == "hidden"
+    ));
 
     Ok(())
 }
@@ -102,6 +113,9 @@ fn test_module_from_ast() -> Result<(), Box<EvalAltResult>> {
         fn add_len(x, y) {
             x + y.len()
         }
+        private fn hidden() {
+            throw "you shouldn't see me!";
+        }
     
         // Imported modules become sub-modules
         import "another module" as extra;
@@ -152,6 +166,12 @@ fn test_module_from_ast() -> Result<(), Box<EvalAltResult>> {
         )?,
         59
     );
+    assert!(matches!(
+        *engine
+            .eval_expression_with_scope::<()>(&mut scope, "testing::hidden()")
+            .expect_err("should error"),
+        EvalAltResult::ErrorFunctionNotFound(fn_name, _) if fn_name == "hidden"
+    ));
 
     Ok(())
 }