Api exposure callbacks

dash/_callback.py

@@ -62,6 +62,7 @@ def _invoke_callback(func, *args, **kwargs):  # used to mark the frame for the d
 GLOBAL_CALLBACK_LIST = []
 GLOBAL_CALLBACK_MAP = {}
 GLOBAL_INLINE_SCRIPTS = []
+GLOBAL_API_PATHS = {}
 
 
 # pylint: disable=too-many-locals
@@ -77,6 +78,7 @@ def callback(
     cache_args_to_ignore: Optional[list] = None,
     cache_ignore_triggered=True,
     on_error: Optional[Callable[[Exception], Any]] = None,
+    api_endpoint: Optional[str] = None,
     optional: Optional[bool] = False,
     **_kwargs,
 ) -> Callable[..., Any]:
@@ -171,6 +173,7 @@ def callback(
     )
     callback_map = _kwargs.pop("callback_map", GLOBAL_CALLBACK_MAP)
     callback_list = _kwargs.pop("callback_list", GLOBAL_CALLBACK_LIST)
+    callback_api_paths = _kwargs.pop("callback_api_paths", GLOBAL_API_PATHS)
 
     if background:
         background_spec: Any = {
@@ -210,12 +213,14 @@ def callback(
         callback_list,
         callback_map,
         config_prevent_initial_callbacks,
+        callback_api_paths,
         *_args,
         **_kwargs,
         background=background_spec,
         manager=manager,
         running=running,
         on_error=on_error,
+        api_endpoint=api_endpoint,
         optional=optional,
     )
 
@@ -581,7 +586,12 @@ def _prepare_response(
 
 # pylint: disable=too-many-branches,too-many-statements
 def register_callback(
-    callback_list, callback_map, config_prevent_initial_callbacks, *_args, **_kwargs
+    callback_list,
+    callback_map,
+    config_prevent_initial_callbacks,
+    callback_api_paths,
+    *_args,
+    **_kwargs,
 ):
     (
         output,
@@ -635,6 +645,10 @@ def register_callback(
 
     # pylint: disable=too-many-locals
     def wrap_func(func):
+        if _kwargs.get("api_endpoint"):
+            api_endpoint = _kwargs.get("api_endpoint")
+            callback_api_paths[api_endpoint] = func
+
         if background is None:
             background_key = None
         else:

dash/dash.py

@@ -568,6 +568,7 @@ def __init__(  # pylint: disable=too-many-statements
         self.callback_map = {}
         # same deps as a list to catch duplicate outputs, and to send to the front end
         self._callback_list = []
+        self.callback_api_paths = {}
 
         # list of inline scripts
         self._inline_scripts = []
@@ -778,6 +779,41 @@ def _setup_routes(self):
         # catch-all for front-end routes, used by dcc.Location
         self._add_url("<path:path>", self.index)
 
+    def setup_apis(self):
+        # Copy over global callback data structures assigned with `dash.callback`
+        for k in list(_callback.GLOBAL_API_PATHS):
+            if k in self.callback_api_paths:
+                raise DuplicateCallback(
+                    f"The callback `{k}` provided with `dash.callback` was already "
+                    "assigned with `app.callback`."
+                )
+            self.callback_api_paths[k] = _callback.GLOBAL_API_PATHS.pop(k)
+
+        def make_parse_body(func):
+            def _parse_body():
+                if flask.request.is_json:
+                    data = flask.request.get_json()
+                    return flask.jsonify(func(**data))
+                return flask.jsonify({})
+
+            return _parse_body
+
+        def make_parse_body_async(func):
+            async def _parse_body_async():
+                if flask.request.is_json:
+                    data = flask.request.get_json()
+                    result = await func(**data)
+                    return flask.jsonify(result)
+                return flask.jsonify({})
+
+            return _parse_body_async
+
+        for path, func in self.callback_api_paths.items():
+            if asyncio.iscoroutinefunction(func):
+                self._add_url(path, make_parse_body_async(func), ["POST"])
+            else:
+                self._add_url(path, make_parse_body(func), ["POST"])
+
     def _setup_plotlyjs(self):
         # pylint: disable=import-outside-toplevel
         from plotly.offline import get_plotlyjs_version
@@ -1356,6 +1392,7 @@ def callback(self, *_args, **_kwargs) -> Callable[..., Any]:
             config_prevent_initial_callbacks=self.config.prevent_initial_callbacks,
             callback_list=self._callback_list,
             callback_map=self.callback_map,
+            callback_api_paths=self.callback_api_paths,
             **_kwargs,
         )
 
@@ -1506,6 +1543,7 @@ def dispatch(self):
     def _setup_server(self):
         if self._got_first_request["setup_server"]:
             return
+
         self._got_first_request["setup_server"] = True
 
         # Apply _force_eager_loading overrides from modules