Python: Verify that plugin names are unique.

python/semantic_kernel/functions/kernel_function_extension.py

@@ -8,7 +8,7 @@
 from pydantic import Field, field_validator
 
 from semantic_kernel.connectors.ai.prompt_execution_settings import PromptExecutionSettings
-from semantic_kernel.exceptions import KernelFunctionNotFoundError, KernelPluginNotFoundError
+from semantic_kernel.exceptions import KernelFunctionNotFoundError, KernelPluginNotFoundError, PluginInvalidNameError
 from semantic_kernel.functions.kernel_function_metadata import KernelFunctionMetadata
 from semantic_kernel.functions.kernel_plugin import KernelPlugin
 from semantic_kernel.kernel_pydantic import KernelBaseModel
@@ -81,24 +81,28 @@ def add_plugin(
             ValidationError: If a KernelPlugin needs to be created, but it is not valid.
 
         """
+        name = plugin.name if isinstance(plugin, KernelPlugin) else plugin_name
+
+        if name in self.plugins:
+            raise PluginInvalidNameError(f"A plugin with the name {name} already exists.")
         if isinstance(plugin, KernelPlugin):
-            self.plugins[plugin.name] = plugin
-            return self.plugins[plugin.name]
-        if not plugin_name:
-            raise ValueError("plugin_name must be provided if a plugin is not supplied.")
+            self.plugins[name] = plugin
+            return self.plugins[name]
+        if not name:
+            raise PluginInvalidNameError("plugin_name must be provided if a plugin is not supplied.")
         if plugin:
-            self.plugins[plugin_name] = KernelPlugin.from_object(
-                plugin_name=plugin_name, plugin_instance=plugin, description=description
+            self.plugins[name] = KernelPlugin.from_object(
+                plugin_name=name, plugin_instance=plugin, description=description
             )
-            return self.plugins[plugin_name]
+            return self.plugins[name]
         if plugin is None and parent_directory is not None:
-            self.plugins[plugin_name] = KernelPlugin.from_directory(
-                plugin_name=plugin_name,
+            self.plugins[name] = KernelPlugin.from_directory(
+                plugin_name=name,
                 parent_directory=parent_directory,
                 description=description,
                 class_init_arguments=class_init_arguments,
             )
-            return self.plugins[plugin_name]
+            return self.plugins[name]
         raise ValueError("plugin or parent_directory must be provided.")
 
     def add_plugins(self, plugins: list[KernelPlugin] | dict[str, KernelPlugin | object]) -> None:

python/tests/unit/kernel/test_kernel.py

@@ -18,6 +18,7 @@
 from semantic_kernel.exceptions import (
     KernelFunctionAlreadyExistsError,
     KernelServiceNotFoundError,
+    PluginInvalidNameError,
     ServiceInvalidTypeError,
 )
 from semantic_kernel.exceptions.kernel_exceptions import KernelFunctionNotFoundError, KernelPluginNotFoundError
@@ -185,7 +186,7 @@ def test_plugin_no_plugin(kernel: Kernel):
 
 
 def test_plugin_name_error(kernel: Kernel):
-    with pytest.raises(ValueError):
+    with pytest.raises(PluginInvalidNameError, match="plugin_name must be provided if a plugin is not supplied."):
         kernel.add_plugin(" ", None)
 
 
@@ -197,6 +198,13 @@ def test_plugins_add_plugins(kernel: Kernel):
     assert len(kernel.plugins) == 2
 
 
+def test_plugins_name_unique(kernel: Kernel):
+    with pytest.raises(PluginInvalidNameError, match="A plugin with the name TestPlugin already exists."):
+        plugin1 = KernelPlugin(name="TestPlugin")
+        plugin2 = KernelPlugin(name="TestPlugin")
+        kernel.add_plugins([plugin1, plugin2])
+
+
 def test_add_function_from_prompt(kernel: Kernel):
     prompt = """
     Write a short story about two Corgis on an adventure.