Address PR feedback

Author: KoolADE85

CHANGELOG.md

@@ -4,6 +4,14 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 
 ## [UNRELEASED]
 
+## [4.3.0rc1] - Unreleased
+
+## Added
+- [#3796](https://github.com/plotly/dash/pull/3796) MCP: Add `configure_mcp_server()` to toggle which content the MCP server exposes (`include_layout`, `include_callbacks`, `include_clientside_callbacks`, `include_pages`, `expose_callback_docstrings`). Only the parameters explicitly passed are updated; omitted parameters retain their current value.
+
+## Changed
+- [#3796](https://github.com/plotly/dash/pull/3796) MCP: Remove the `mcp_expose_docstrings` `Dash()` constructor argument; callback docstring exposure is now controlled via `configure_mcp_server(expose_callback_docstrings=...)`.
+
 ## [4.3.0rc0] - 2026-05-21
 
 ## Added

dash/mcp/_configure.py

@@ -6,6 +6,8 @@
 
 from __future__ import annotations
 
+from typing import Optional
+
 from dash import get_app
 from dash.exceptions import AppNotFoundError
 from dash.mcp.primitives.resources import _RESOURCE_PROVIDERS as MCP_RESOURCE_PROVIDERS
@@ -23,20 +25,37 @@
 _ALL_MCP_RESOURCE_PROVIDERS = list(MCP_RESOURCE_PROVIDERS)
 _ALL_MCP_TOOL_PROVIDERS = list(MCP_TOOL_PROVIDERS)
 
+# Membership groupings (order-independent): which providers each toggle
+# controls. The exposed order is owned solely by the registry lists.
+_LAYOUT_RESOURCES = {LayoutResource, ComponentsResource}
+_CLIENTSIDE_CALLBACK_RESOURCES = {ClientsideCallbacksResource}
+_PAGE_RESOURCES = {PagesResource, PageLayoutResource}
+_LAYOUT_TOOLS = {GetDashComponentTool}
+
+_DEFAULT_CONFIG = {
+    "include_layout": True,
+    "include_callbacks": True,
+    "include_clientside_callbacks": True,
+    "include_pages": True,
+    "expose_callback_docstrings": False,
+}
+_current_config = dict(_DEFAULT_CONFIG)
+
 
 def configure_mcp_server(
     *,
-    include_layout: bool = True,
-    include_callbacks: bool = True,
-    include_clientside_callbacks: bool = True,
-    include_pages: bool = True,
-    expose_callback_docstrings: bool = False,
+    include_layout: Optional[bool] = None,
+    include_callbacks: Optional[bool] = None,
+    include_clientside_callbacks: Optional[bool] = None,
+    include_pages: Optional[bool] = None,
+    expose_callback_docstrings: Optional[bool] = None,
 ) -> None:
     """
     Configure which content the Dash MCP server exposes.
 
-    Any parameter that is omitted will be reset to its default value. Calling
-    with no args will reset all configuration to its default state.
+    Only the parameters that are explicitly passed are updated; any parameter
+    that is omitted keeps its current value. On the first call, unset values
+    take their defaults (all content included except callback docstrings).
 
     :param include_layout: Expose ``dash://layout``, ``dash://components``,
         and the ``get_dash_component`` tool.  Defaults to ``True``.
@@ -66,25 +85,49 @@ def configure_mcp_server(
         if get_app().backend.has_request_context():
             raise RuntimeError("MCP server can't be configured within a callback")
     except AppNotFoundError:
-        ...
-
-    CallbackTools.callbacks_mcp_enabled_by_default = include_callbacks
-    CallbackTools.expose_docstrings_by_default = expose_callback_docstrings
-
-    updated_resources = list(_ALL_MCP_RESOURCE_PROVIDERS)
-    if not include_layout:
-        updated_resources.remove(LayoutResource)
-        updated_resources.remove(ComponentsResource)
-    if not include_clientside_callbacks:
-        updated_resources.remove(ClientsideCallbacksResource)
-    if not include_pages:
-        updated_resources.remove(PagesResource)
-        updated_resources.remove(PageLayoutResource)
-    MCP_RESOURCE_PROVIDERS[:] = updated_resources
-
-    updated_tools = list(_ALL_MCP_TOOL_PROVIDERS)
-    if not include_layout:
-        updated_tools.remove(GetDashComponentTool)
-    MCP_TOOL_PROVIDERS[:] = updated_tools
-
-    get_app().mcp_callback_map = None
+        pass
+
+    passed = {
+        "include_layout": include_layout,
+        "include_callbacks": include_callbacks,
+        "include_clientside_callbacks": include_clientside_callbacks,
+        "include_pages": include_pages,
+        "expose_callback_docstrings": expose_callback_docstrings,
+    }
+    _current_config.update(
+        {key: value for key, value in passed.items() if value is not None}
+    )
+
+    CallbackTools.callbacks_mcp_enabled_by_default = _current_config[
+        "include_callbacks"
+    ]
+    CallbackTools.expose_docstrings_by_default = _current_config[
+        "expose_callback_docstrings"
+    ]
+
+    excluded_resources: set = set()
+    if not _current_config["include_layout"]:
+        excluded_resources |= _LAYOUT_RESOURCES
+    if not _current_config["include_clientside_callbacks"]:
+        excluded_resources |= _CLIENTSIDE_CALLBACK_RESOURCES
+    if not _current_config["include_pages"]:
+        excluded_resources |= _PAGE_RESOURCES
+    MCP_RESOURCE_PROVIDERS[:] = [
+        resource
+        for resource in _ALL_MCP_RESOURCE_PROVIDERS
+        if resource not in excluded_resources
+    ]
+
+    excluded_tools: set = set()
+    if not _current_config["include_layout"]:
+        excluded_tools |= _LAYOUT_TOOLS
+    MCP_TOOL_PROVIDERS[:] = [
+        tool for tool in _ALL_MCP_TOOL_PROVIDERS if tool not in excluded_tools
+    ]
+
+    # Invalidate the cached callback map so it is rebuilt with the new config.
+    # No app yet (configured before `Dash()`) means there is no cache to clear.
+    try:
+        get_app().mcp_callback_map = None
+    except AppNotFoundError:
+        pass

tests/integration/mcp/conftest.py

@@ -20,6 +20,10 @@
     from dash.mcp.primitives.tools.tools_callbacks import (  # pylint: disable=wrong-import-position
         CallbackTools,
     )
+    from dash.mcp._decorator import (  # pylint: disable=wrong-import-position
+        MCP_DECORATED_FUNCTIONS,
+    )
+    from dash.mcp import _configure  # pylint: disable=wrong-import-position
 
 
 @pytest.fixture(autouse=True)
@@ -42,6 +46,8 @@ def _reset_dash_app_state():
     _TOOL_PROVIDERS[:] = initial_tools
     CallbackTools.callbacks_mcp_enabled_by_default = initial_callbacks_default
     CallbackTools.expose_docstrings_by_default = initial_expose_docstrings
+    MCP_DECORATED_FUNCTIONS.clear()
+    _configure._current_config = dict(_configure._DEFAULT_CONFIG)
     _get_app.APP = None
     _get_app.app_context.set(None)
 

tests/integration/mcp/test_mcp_configure.py

@@ -93,3 +93,30 @@ def included(val):
     resources = _mcp_method(dash_duo.server.url, "resources/list")
     uris = [r["uri"] for r in resources["result"]["resources"]]
     assert "dash://layout" in uris
+
+
+def test_mcpcfg004_configure_before_app_governs_live_server(dash_duo):
+    """configure_mcp_server() called BEFORE Dash() still governs the running
+    server: app construction and the first request do not reset the config."""
+    # Configure before the app exists.
+    configure_mcp_server(include_layout=False, include_callbacks=False)
+
+    app = Dash(__name__)
+    app.layout = html.Div([dcc.Input(id="inp"), html.Div(id="out")])
+
+    @app.callback(Output("out", "children"), Input("inp", "value"), mcp_enabled=True)
+    def included(val):
+        return val
+
+    dash_duo.start_server(app)
+
+    # First real request builds the callback map; pre-app config must hold.
+    tools = _mcp_tools(dash_duo.server.url)
+    tool_names = [t["name"] for t in tools]
+    assert "included" in tool_names  # opt-in honored under include_callbacks=False
+    assert "get_dash_component" not in tool_names  # include_layout=False honored
+
+    resources = _mcp_method(dash_duo.server.url, "resources/list")
+    uris = [r["uri"] for r in resources["result"]["resources"]]
+    assert "dash://layout" not in uris
+    assert "dash://components" not in uris

tests/unit/mcp/test_mcp_configure.py

@@ -46,10 +46,13 @@ def _reset_mcp_module_state():
     """Restore module-level MCP state after every test."""
     yield
 
+    from dash.mcp import _configure
+
     CallbackTools.callbacks_mcp_enabled_by_default = True
     CallbackTools.expose_docstrings_by_default = False
     _RESOURCE_PROVIDERS[:] = list(_DEFAULT_RESOURCE_PROVIDERS)
     _TOOL_PROVIDERS[:] = list(_DEFAULT_TOOL_PROVIDERS)
+    _configure._current_config = dict(_configure._DEFAULT_CONFIG)
     _get_app_module.APP = None
     _get_app_module.app_context.set(None)
 
@@ -220,3 +223,60 @@ def test_mcpc007_configure_mcp_invalidates_mcp_callback_map():
     configure_mcp_server(include_callbacks=False)
 
     assert app.mcp_callback_map is None
+
+
+# ---------------------------------------------------------------------------
+# Patch-style semantics: omitted params retain their previous value
+# ---------------------------------------------------------------------------
+
+
+def test_mcpc009_omitted_params_retain_previous_value():
+    """A subsequent call only updates the params it is passed; previously-set
+    values persist instead of resetting to their defaults."""
+    _make_app()
+
+    configure_mcp_server(include_layout=False)
+    assert LayoutResource not in _RESOURCE_PROVIDERS
+    assert GetDashComponentTool not in _TOOL_PROVIDERS
+
+    # Touch an unrelated knob; include_layout must stay disabled.
+    configure_mcp_server(include_pages=False)
+
+    assert LayoutResource not in _RESOURCE_PROVIDERS
+    assert GetDashComponentTool not in _TOOL_PROVIDERS
+    assert PagesResource not in _RESOURCE_PROVIDERS
+
+
+# ---------------------------------------------------------------------------
+# Configuring before the app survives construction and first-request build
+# ---------------------------------------------------------------------------
+
+
+def test_mcpc010_configure_before_app_survives_construction():
+    """Config applied before `Dash()` exists is not reset by `Dash.__init__`:
+    provider lists set pre-app remain in effect after construction."""
+    # Configure first, with no app in context (must not raise).
+    configure_mcp_server(include_layout=False)
+
+    # Constructing the app must not restore the disabled providers.
+    _make_app()
+
+    assert LayoutResource not in _RESOURCE_PROVIDERS
+    assert ComponentsResource not in _RESOURCE_PROVIDERS
+    assert GetDashComponentTool not in _TOOL_PROVIDERS
+
+
+def test_mcpc011_configure_before_app_governs_callback_filter_mode():
+    """`include_callbacks=False` set before `Dash()` still governs how the
+    callback map is built on first request (opt-in mode is honored)."""
+    # Configure opt-in mode before any app exists.
+    configure_mcp_server(include_callbacks=False)
+
+    # App built afterward; its single callback does not opt in.
+    app_none = _make_app()  # mcp_enabled defaults to None
+    # The collection is built lazily (as on first request) and must reflect
+    # the pre-app opt-in config: the non-opted-in callback is excluded.
+    assert len(_collection(app_none)) == 0
+
+    app_opted_in = _make_app(mcp_enabled=True)
+    assert len(_collection(app_opted_in)) == 1