feat!: prevent binding the same interface more than once

BREAKING CHANGE: The 'to' and 'to_factory' methods of BindingBuilder now return 'Result'

3 files changed, 52 insertions, 14 deletions

diff --git a/src/di_container.rs b/src/di_container.rs
index e15d921..c33d339 100644
--- a/src/di_container.rs
+++ b/src/di_container.rs
@@ -92,20 +92,33 @@ where
 
     /// Creates a binding of type `Interface` to type `Implementation` inside of the
     /// associated [`DIContainer`].
-    pub fn to<Implementation>(&mut self)
+    ///
+    /// # Errors
+    /// Will return Err if the associated [`DIContainer`] already have a binding for
+    /// the interface.
+    pub fn to<Implementation>(&mut self) -> error_stack::Result<(), BindingBuilderError>
     where
         Implementation: Injectable,
     {
         self.di_container
             .bindings
-            .set::<Interface>(Box::new(TransientTypeProvider::<Implementation>::new()));
+            .set::<Interface>(Box::new(TransientTypeProvider::<Implementation>::new()))
+            .ok_or_else(|| {
+                report!(BindingBuilderError).attach_printable(format!(
+                    "Binding already exists for interface '{}'",
+                    type_name::<Interface>()
+                ))
+            })?;
+
+        Ok(())
     }
 
     /// Creates a binding of type `Interface` to a new singleton of type `Implementation`
     /// inside of the associated [`DIContainer`].
     ///
     /// # Errors
-    /// Will return Err if creating the singleton fails.
+    /// Will return Err if creating the singleton fails or if the
+    /// associated [`DIContainer`] already have a binding for the interface.
     pub fn to_singleton<Implementation>(
         &mut self,
     ) -> error_stack::Result<(), BindingBuilderError>
@@ -119,7 +132,13 @@ where
 
         self.di_container
             .bindings
-            .set::<Interface>(Box::new(SingletonProvider::new(singleton)));
+            .set::<Interface>(Box::new(SingletonProvider::new(singleton)))
+            .ok_or_else(|| {
+                report!(BindingBuilderError).attach_printable(format!(
+                    "Binding already exists for interface '{}'",
+                    type_name::<Interface>()
+                ))
+            })?;
 
         Ok(())
     }
@@ -128,22 +147,35 @@ where
     /// associated [`DIContainer`].
     ///
     /// *This function is only available if Syrette is built with the "factory" feature.*
+    ///
+    /// # Errors
+    /// Will return Err if the associated [`DIContainer`] already have a binding for
+    /// the interface.
     #[cfg(feature = "factory")]
     pub fn to_factory<Args, Return>(
         &mut self,
         factory_func: &'static dyn Fn<Args, Output = TransientPtr<Return>>,
-    ) where
+    ) -> error_stack::Result<(), BindingBuilderError>
+    where
         Args: 'static,
         Return: 'static + ?Sized,
         Interface: crate::interfaces::factory::IFactory<Args, Return>,
     {
         let factory_impl = CastableFactory::new(factory_func);
 
-        self.di_container.bindings.set::<Interface>(Box::new(
-            crate::provider::FactoryProvider::new(crate::ptr::FactoryPtr::new(
-                factory_impl,
-            )),
-        ));
+        self.di_container
+            .bindings
+            .set::<Interface>(Box::new(crate::provider::FactoryProvider::new(
+                crate::ptr::FactoryPtr::new(factory_impl),
+            )))
+            .ok_or_else(|| {
+                report!(BindingBuilderError).attach_printable(format!(
+                    "Binding already exists for interface '{}'",
+                    type_name::<Interface>()
+                ))
+            })?;
+
+        Ok(())
     }
 }
 
diff --git a/src/di_container_binding_map.rs b/src/di_container_binding_map.rs
index b505321..fee33b0 100644
--- a/src/di_container_binding_map.rs
+++ b/src/di_container_binding_map.rs
@@ -30,23 +30,29 @@ impl DIContainerBindingMap
             .get(&interface_typeid)
             .ok_or_else(|| {
                 report!(DIContainerError).attach_printable(format!(
-                    "No binding exists for {}",
+                    "No binding exists for interface '{}'",
                     type_name::<Interface>()
                 ))
             })?
             .as_ref())
     }
 
-    pub fn set<Interface>(&mut self, provider: Box<dyn IProvider>)
+    pub fn set<Interface>(&mut self, provider: Box<dyn IProvider>) -> Option<()>
     where
         Interface: 'static + ?Sized,
     {
         let interface_typeid = TypeId::of::<Interface>();
 
+        if self.bindings.contains_key(&interface_typeid) {
+            return None;
+        }
+
         self.bindings.insert(interface_typeid, provider);
+
+        Some(())
     }
 
-    /// Only used by tests in the ``di_container`` module.
+    /// Only used by tests in the `di_container` module.
     #[cfg(test)]
     pub fn count(&self) -> usize
     {
diff --git a/src/lib.rs b/src/lib.rs
index a03675b..89688f1 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -40,7 +40,7 @@ mod provider;
 #[macro_export]
 macro_rules! di_container_bind {
     ($interface: path => $implementation: ty, $di_container: ident) => {
-        $di_container.bind::<dyn $interface>().to::<$implementation>();
+        $di_container.bind::<dyn $interface>().to::<$implementation>().unwrap();
 
         syrette::declare_interface!($implementation -> $interface);
     };