Create TableProxy trait and some table tests

src/table.rs

@@ -279,6 +279,14 @@ impl<'a> Table<'a> {
 
         Ok(())
     }
+
+    pub fn try_into<T: TableProxy>(self) -> Result<T> {
+        T::from_table(self.state, self)
+    }
+
+    pub fn try_from<T: TableProxy + Sized>(state: &'a State, proxy: T) -> Result<Table<'a>> {
+        proxy.as_table(state)
+    }
 }
 
 impl<'a> PushToLuaStack<'a> for Table<'a> {
@@ -298,7 +306,159 @@ impl<'a> FromLuaStack<'a> for Table<'a> {
 }
 
 impl<'a> FromLua<'a> for Table<'a> {
-    fn from_lua(_lua: &'a State, val: Value<'a>) -> crate::Result<Self> {
+    fn from_lua(_: &'a State, val: Value<'a>) -> crate::Result<Self> {
         val.into_table()
     }
 }
+
+impl<'a> AsLua<'a> for Table<'a> {
+    fn as_lua(&self, _: &'a State) -> crate::Result<Value<'a>> {
+        Ok(Value::Table(self.clone()))
+    }
+}
+
+/// This trait is used for proxying a Rust type to and from Lua as a Lua table. In Lua, you can
+/// make a representation of your Rust type, then implement this trait on the Rust type. This
+/// trait allows you to put your Rust type into Lua as the type you created in Lua, and you can
+/// also retrieve an instance of your Rust type from an instance of the Lua type. This could help
+/// with minimizing the amount of calls to and from Rust.
+pub trait TableProxy: Sized {
+    /// Create an instance of `Self` from the table
+    fn from_table<'a>(state: &'a State, table: Table<'a>) -> Result<Self>;
+    /// Creates a Lua instance from `Self`
+    fn as_table<'a>(&self, state: &'a State) -> Result<Table<'a>>;
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::{tests::Vec2, Function, State, StdLibrary, Table, TableProxy};
+
+    impl TableProxy for Vec2 {
+        fn from_table<'a>(_state: &'a crate::State, table: crate::Table<'a>) -> crate::Result<Self> {
+            let x: f32 = table.get("x")?;
+            let y: f32 = table.get("y")?;
+
+            Ok(Vec2 {
+                x,
+                y,
+            })
+        }
+
+        fn as_table<'a>(&self, state: &'a crate::State) -> crate::Result<crate::Table<'a>> {
+            let globals = state.globals()?;
+            let vec2: Table = globals.get("Vec2")?;
+            let new_fn: Function = vec2.get("new")?;
+            new_fn.exec((vec2, self.x, self.y))
+        }
+    }
+
+    #[test]
+    fn table_get() -> crate::Result<()> {
+        let lua = State::new();
+        lua.expose_libraries(&[StdLibrary::Debug, StdLibrary::Package]);
+    
+        let res = lua.load(
+            "test.lua",
+            r#"
+                text = "Hello, World"
+        "#)?.execute::<_, ()>(());
+
+        // pretty print the error
+        if let Err(err) = res {
+            panic!("{}", err);
+        }
+
+        let globals = lua.globals()?;
+        let text: String = globals.get("text")?;
+        assert_eq!(text, "Hello, World".to_string());
+
+        Ok(())
+    }
+
+    #[test]
+    fn table_set() -> crate::Result<()> {
+        let lua = State::new();
+        lua.expose_libraries(&[StdLibrary::Debug, StdLibrary::Package]);
+    
+        let globals = lua.globals()?;
+        globals.set("text", "Hello, World")?;
+
+        let res = lua.load(
+            "test.lua",
+            r#"
+                assert(text == "Hello, World", "The text was not set correctly")
+        "#)?.execute::<_, ()>(());
+
+        // pretty print the error
+        if let Err(err) = res {
+            panic!("{}", err);
+        }
+
+        Ok(())
+    }
+
+    #[test]
+    fn table_proxy() -> crate::Result<()> {
+        let lua = State::new();
+        lua.expose_libraries(&[StdLibrary::Debug, StdLibrary::Package]);
+    
+        let res = lua.load(
+            "test.lua",
+            r#"
+                Vec2 = { x = 0.0, y = 0.0 }
+                Vec2.__index = Vec2
+                Vec2.__name = "Vec2"
+                
+                function Vec2:new(x, y)
+                    local v = {}
+                    setmetatable(v, Vec2)
+                    
+                    v.x = x
+                    v.y = y
+                    
+                    return v
+                end
+
+                function Vec2:__tostring()
+                    return "Vec2(" .. self.x .. ", " .. self.y .. ")"
+                end
+
+                function do_math()
+                    return Vec2:new(15, 20)
+                end
+        "#)?.execute::<_, ()>(());
+
+        // pretty print the error
+        if let Err(err) = res {
+            panic!("{}", err);
+        }
+
+        let globals = lua.globals()?;
+        let math_fn: Function = globals.get("do_math")?;
+        let lua_vec2: Table = math_fn.exec(())?;
+        let mut vec2 = Vec2::from_table(&lua, lua_vec2)?;
+        assert_eq!(vec2.x, 15.0);
+        assert_eq!(vec2.y, 20.0);
+
+        vec2.x *= 2.0;
+        vec2.y *= 2.0;
+
+        globals.set("pos", vec2.as_table(&lua)?)?;
+
+        let res = lua.load(
+            "test.lua",
+            r#"
+                -- Vec2 stuff is included from last chunk
+
+                assert(type(pos) == "table", "The global 'pos' is not a table like expected of 'as_table'!!")
+                print("pos is " .. tostring(pos))
+        "#)?.execute::<_, ()>(());
+        
+        // pretty print the error
+        if let Err(err) = res {
+            panic!("{}", err);
+        }
+
+        Ok(())
+    }
+}