Fix duplicate asset loader registration warning (#17105)

# Objective

The original fix (#11870) did not actually implement the
described logic. It checked if there were independently multiple loaders
for a given asset type and multiple loaders for a given extension.
However, this did not handle the case where those loaders were not the
same. For example, there could be a loader for type `Foo` and extension
`.foo`. Anther loader could exist for type `Bar` but extension `.bar`.
If a third loader was added for type `Foo` but extension `.bar`, the
warning would have been incorrectly logged.

## Solution

Instead of independently checking to see if there are preexisting
loaders for both the extension and type, look up the indices of the
loaders for the type in question. Then check to see if the loaders
registered for the extensions has any overlap. Only log if there are
loaders that fit this criteria.

## Testing

Ran CI tests. Locally tested the situation describe in the objective
section for the normal `App::init_asset_loader` flow. I think testing
could be done on the pre-registration flow for loaders still. I tested
on Windows, but the changes should not be affected by platform.

Author: arunke

crates/bevy_asset/src/server/loaders.rs

@@ -47,6 +47,7 @@ impl AssetLoaders {
             };
 
         if is_new {
+            let existing_loaders_for_type_id = self.type_id_to_loaders.get(&loader_asset_type);
             let mut duplicate_extensions = Vec::new();
             for extension in AssetLoader::extensions(&*loader) {
                 let list = self
@@ -55,26 +56,29 @@ impl AssetLoaders {
                     .or_default();
 
                 if !list.is_empty() {
-                    duplicate_extensions.push(extension);
+                    if let Some(existing_loaders_for_type_id) = existing_loaders_for_type_id {
+                        if list
+                            .iter()
+                            .any(|index| existing_loaders_for_type_id.contains(index))
+                        {
+                            duplicate_extensions.push(extension);
+                        }
+                    }
                 }
 
                 list.push(loader_index);
             }
-
-            self.type_name_to_loader.insert(type_name, loader_index);
-
-            let list = self
-                .type_id_to_loaders
-                .entry(loader_asset_type)
-                .or_default();
-
-            let duplicate_asset_registration = !list.is_empty();
-            if !duplicate_extensions.is_empty() && duplicate_asset_registration {
+            if !duplicate_extensions.is_empty() {
                 warn!("Duplicate AssetLoader registered for Asset type `{loader_asset_type_name}` with extensions `{duplicate_extensions:?}`. \
                 Loader must be specified in a .meta file in order to load assets of this type with these extensions.");
             }
 
-            list.push(loader_index);
+            self.type_name_to_loader.insert(type_name, loader_index);
+
+            self.type_id_to_loaders
+                .entry(loader_asset_type)
+                .or_default()
+                .push(loader_index);
 
             self.loaders.push(MaybeAssetLoader::Ready(loader));
         } else {
@@ -108,6 +112,8 @@ impl AssetLoaders {
 
         self.preregistered_loaders.insert(type_name, loader_index);
         self.type_name_to_loader.insert(type_name, loader_index);
+
+        let existing_loaders_for_type_id = self.type_id_to_loaders.get(&loader_asset_type);
         let mut duplicate_extensions = Vec::new();
         for extension in extensions {
             let list = self
@@ -116,24 +122,27 @@ impl AssetLoaders {
                 .or_default();
 
             if !list.is_empty() {
-                duplicate_extensions.push(extension);
+                if let Some(existing_loaders_for_type_id) = existing_loaders_for_type_id {
+                    if list
+                        .iter()
+                        .any(|index| existing_loaders_for_type_id.contains(index))
+                    {
+                        duplicate_extensions.push(extension);
+                    }
+                }
             }
 
             list.push(loader_index);
         }
-
-        let list = self
-            .type_id_to_loaders
-            .entry(loader_asset_type)
-            .or_default();
-
-        let duplicate_asset_registration = !list.is_empty();
-        if !duplicate_extensions.is_empty() && duplicate_asset_registration {
+        if !duplicate_extensions.is_empty() {
             warn!("Duplicate AssetLoader preregistered for Asset type `{loader_asset_type_name}` with extensions `{duplicate_extensions:?}`. \
             Loader must be specified in a .meta file in order to load assets of this type with these extensions.");
         }
 
-        list.push(loader_index);
+        self.type_id_to_loaders
+            .entry(loader_asset_type)
+            .or_default()
+            .push(loader_index);
 
         let (mut sender, receiver) = async_broadcast::broadcast(1);
         sender.set_overflow(true);