feat: add support for external plugins

Signed-off-by: Teryl Taylor <[email protected]>

Author: Teryl Taylor

mcpgateway/config.py

@@ -557,9 +557,7 @@ def validate_database(self) -> None:
                 db_dir.mkdir(parents=True)
 
     # Validation patterns for safe display (configurable)
-    validation_dangerous_html_pattern: str = (
-        r"<(script|iframe|object|embed|link|meta|base|form|img|svg|video|audio|source|track|area|map|canvas|applet|frame|frameset|html|head|body|style)\b|</*(script|iframe|object|embed|link|meta|base|form|img|svg|video|audio|source|track|area|map|canvas|applet|frame|frameset|html|head|body|style)>"
-    )
+    validation_dangerous_html_pattern: str = r"<(script|iframe|object|embed|link|meta|base|form|img|svg|video|audio|source|track|area|map|canvas|applet|frame|frameset|html|head|body|style)\b|</*(script|iframe|object|embed|link|meta|base|form|img|svg|video|audio|source|track|area|map|canvas|applet|frame|frameset|html|head|body|style)>"
 
     validation_dangerous_js_pattern: str = r"(?i)(?:^|\s|[\"'`<>=])(javascript:|vbscript:|data:\s*[^,]*[;\s]*(javascript|vbscript)|\bon[a-z]+\s*=|<\s*script\b)"
 

mcpgateway/plugins/__init__.py

@@ -13,14 +13,7 @@
 """
 
 from mcpgateway.plugins.framework.manager import PluginManager
-from mcpgateway.plugins.framework.models import PluginViolation
-from mcpgateway.plugins.framework.plugin_types import GlobalContext, PluginViolationError, PromptPosthookPayload, PromptPrehookPayload
+from mcpgateway.plugins.framework.models import GlobalContext, PluginViolation, PromptPosthookPayload, PromptPrehookPayload, ToolPostInvokePayload, ToolPreInvokePayload
+from mcpgateway.plugins.framework.errors import PluginViolationError, PluginError
 
-__all__ = [
-    "GlobalContext",
-    "PluginManager",
-    "PluginViolation",
-    "PluginViolationError",
-    "PromptPosthookPayload",
-    "PromptPrehookPayload",
-]
+__all__ = ["GlobalContext", "PluginError", "PluginManager", "PluginViolation", "PluginViolationError", "PromptPosthookPayload", "PromptPrehookPayload", "ToolPostInvokePayload", "ToolPreInvokePayload"]

mcpgateway/plugins/framework/base.py

@@ -20,9 +20,12 @@
 import uuid
 
 # First-Party
-from mcpgateway.plugins.framework.models import HookType, PluginCondition, PluginConfig, PluginMode
-from mcpgateway.plugins.framework.plugin_types import (
+from mcpgateway.plugins.framework.models import (
+    HookType,
+    PluginCondition,
+    PluginConfig,
     PluginContext,
+    PluginMode,
     PromptPosthookPayload,
     PromptPosthookResult,
     PromptPrehookPayload,
@@ -138,6 +141,9 @@ def conditions(self) -> list[PluginCondition] | None:
         """
         return self._config.conditions
 
+    async def initialize(self) -> None:
+        """Initialize the plugin."""
+
     async def prompt_pre_fetch(self, payload: PromptPrehookPayload, context: PluginContext) -> PromptPrehookResult:
         """Plugin hook run before a prompt is retrieved and rendered.
 
@@ -177,18 +183,14 @@ async def tool_pre_invoke(self, payload: ToolPreInvokePayload, context: PluginCo
             payload: The tool payload to be analyzed.
             context: Contextual information about the hook call.
 
-        Returns:
-            ToolPreInvokeResult with processing status and modified payload.
-
-        Examples:
-            >>> from mcpgateway.plugins.framework.plugin_types import ToolPreInvokePayload, PluginContext, GlobalContext
-            >>> payload = ToolPreInvokePayload("calculator", {"operation": "add", "a": 5, "b": 3})
-            >>> context = PluginContext(GlobalContext(request_id="123"))
-            >>> # In async context:
-            >>> # result = await plugin.tool_pre_invoke(payload, context)
+        Raises:
+            NotImplementedError: needs to be implemented by sub class.
         """
-        # Default pass-through implementation
-        return ToolPreInvokeResult(continue_processing=True, modified_payload=payload)
+        raise NotImplementedError(
+            f"""'tool_pre_invoke' not implemented for plugin {self._config.name}
+                                    of plugin type {type(self)}
+                                   """
+        )
 
     async def tool_post_invoke(self, payload: ToolPostInvokePayload, context: PluginContext) -> ToolPostInvokeResult:
         """Plugin hook run after a tool is invoked.
@@ -197,18 +199,14 @@ async def tool_post_invoke(self, payload: ToolPostInvokePayload, context: Plugin
             payload: The tool result payload to be analyzed.
             context: Contextual information about the hook call.
 
-        Returns:
-            ToolPostInvokeResult with processing status and modified result.
-
-        Examples:
-            >>> from mcpgateway.plugins.framework.plugin_types import ToolPostInvokePayload, PluginContext, GlobalContext
-            >>> payload = ToolPostInvokePayload("calculator", {"result": 8, "status": "success"})
-            >>> context = PluginContext(GlobalContext(request_id="123"))
-            >>> # In async context:
-            >>> # result = await plugin.tool_post_invoke(payload, context)
+        Raises:
+            NotImplementedError: needs to be implemented by sub class.
         """
-        # Default pass-through implementation
-        return ToolPostInvokeResult(continue_processing=True, modified_payload=payload)
+        raise NotImplementedError(
+            f"""'tool_post_invoke' not implemented for plugin {self._config.name}
+                                    of plugin type {type(self)}
+                                   """
+        )
 
     async def resource_pre_fetch(self, payload, context):
         """Plugin hook run before a resource is fetched.
@@ -217,22 +215,14 @@ async def resource_pre_fetch(self, payload, context):
             payload: The resource payload to be analyzed.
             context: Contextual information about the hook call.
 
-        Returns:
-            ResourcePreFetchResult with processing status and modified payload.
-
-        Examples:
-            >>> from mcpgateway.plugins.framework.plugin_types import ResourcePreFetchPayload, PluginContext, GlobalContext
-            >>> payload = ResourcePreFetchPayload("file:///data.txt", {"cache": True})
-            >>> context = PluginContext(GlobalContext(request_id="123"))
-            >>> # In async context:
-            >>> # result = await plugin.resource_pre_fetch(payload, context)
+        Raises:
+            NotImplementedError: needs to be implemented by sub class.
         """
-        # Import here to avoid circular dependency
-        # First-Party
-        from mcpgateway.plugins.framework.plugin_types import ResourcePreFetchResult
-
-        # Default pass-through implementation
-        return ResourcePreFetchResult(continue_processing=True, modified_payload=payload)
+        raise NotImplementedError(
+            f"""'resource_pre_fetch' not implemented for plugin {self._config.name}
+                                    of plugin type {type(self)}
+                                   """
+        )
 
     async def resource_post_fetch(self, payload, context):
         """Plugin hook run after a resource is fetched.
@@ -241,24 +231,14 @@ async def resource_post_fetch(self, payload, context):
             payload: The resource content payload to be analyzed.
             context: Contextual information about the hook call.
 
-        Returns:
-            ResourcePostFetchResult with processing status and modified content.
-
-        Examples:
-            >>> from mcpgateway.plugins.framework.plugin_types import ResourcePostFetchPayload, PluginContext, GlobalContext
-            >>> from mcpgateway.models import ResourceContent
-            >>> content = ResourceContent(type="resource", uri="file:///data.txt", text="Data")
-            >>> payload = ResourcePostFetchPayload("file:///data.txt", content)
-            >>> context = PluginContext(GlobalContext(request_id="123"))
-            >>> # In async context:
-            >>> # result = await plugin.resource_post_fetch(payload, context)
+        Raises:
+            NotImplementedError: needs to be implemented by sub class.
         """
-        # Import here to avoid circular dependency
-        # First-Party
-        from mcpgateway.plugins.framework.plugin_types import ResourcePostFetchResult
-
-        # Default pass-through implementation
-        return ResourcePostFetchResult(continue_processing=True, modified_payload=payload)
+        raise NotImplementedError(
+            f"""'resource_post_fetch' not implemented for plugin {self._config.name}
+                                    of plugin type {type(self)}
+                                   """
+        )
 
     async def shutdown(self) -> None:
         """Plugin cleanup code."""

mcpgateway/plugins/framework/constants.py

@@ -0,0 +1,27 @@
+# -*- coding: utf-8 -*-
+"""Plugins constants file.
+
+Copyright 2025
+SPDX-License-Identifier: Apache-2.0
+Authors: Teryl Taylor
+
+This module stores a collection of plugin constants used throughout the framework.
+"""
+
+# Model constants.
+# Specialized plugin types.
+EXTERNAL_PLUGIN_TYPE = "external"
+
+# MCP related constants.
+PYTHON_SUFFIX = ".py"
+URL = "url"
+SCRIPT = "script"
+AFTER = "after"
+
+NAME = "name"
+PYTHON = "python"
+PLUGIN_NAME = "plugin_name"
+PAYLOAD = "payload"
+CONTEXT = "context"
+GET_PLUGIN_CONFIG = "get_plugin_config"
+IGNORE_CONFIG_EXTERNAL = "ignore_config_external"

mcpgateway/plugins/framework/errors.py

@@ -0,0 +1,63 @@
+# -*- coding: utf-8 -*-
+"""Pydantic models for plugins.
+
+Copyright 2025
+SPDX-License-Identifier: Apache-2.0
+Authors: Teryl Taylor
+
+This module implements the pydantic models associated with
+the base plugin layer including configurations, and contexts.
+"""
+
+# First-Party
+from mcpgateway.plugins.framework.models import PluginErrorModel, PluginViolation
+
+
+class PluginViolationError(Exception):
+    """A plugin violation error.
+
+    Attributes:
+        violation (PluginViolation): the plugin violation.
+        message (str): the plugin violation reason.
+    """
+
+    def __init__(self, message: str, violation: PluginViolation | None = None):
+        """Initialize a plugin violation error.
+
+        Args:
+            message: the reason for the violation error.
+            violation: the plugin violation object details.
+        """
+        self.message = message
+        self.violation = violation
+        super().__init__(self.message)
+
+
+class PluginError(Exception):
+    """A plugin error object for errors internal to the plugin.
+
+    Attributes:
+        error (PluginErrorModel): the plugin error object.
+    """
+
+    def __init__(self, error: PluginErrorModel):
+        """Initialize a plugin violation error.
+
+        Args:
+            error: the plugin error details.
+        """
+        self.error = error
+        super().__init__(self.error.message)
+
+
+def convert_exception_to_error(exception: Exception, plugin_name: str) -> PluginErrorModel:
+    """Converts an exception object into a PluginErrorModel. Primarily used for external plugin error handling.
+
+    Args:
+        exception: The exception to be converted.
+        plugin_name: The name of the plugin on which the exception occurred.
+
+    Returns:
+        A plugin error pydantic object that can be sent over HTTP.
+    """
+    return PluginErrorModel(message=repr(exception), plugin_name=plugin_name)