adding support for async callbacks and page layouts

Author: BSd3v

dash/_callback.py

@@ -4,6 +4,7 @@
 from typing import Callable, Optional, Any
 
 import flask
+import asyncio
 
 from .dependencies import (
     handle_callback_args,
@@ -39,8 +40,13 @@
 from ._callback_context import context_value
 
 
-def _invoke_callback(func, *args, **kwargs):  # used to mark the frame for the debugger
-    return func(*args, **kwargs)  # %% callback invoked %%
+async def _invoke_callback(func, *args, **kwargs):
+    # Check if the function is a coroutine function
+    if asyncio.iscoroutinefunction(func):
+        return await func(*args, **kwargs)
+    else:
+        # If the function is not a coroutine, call it directly
+        return func(*args, **kwargs)
 
 
 class NoUpdate:
@@ -353,7 +359,7 @@ def wrap_func(func):
             )
 
         @wraps(func)
-        def add_context(*args, **kwargs):
+        async def add_context(*args, **kwargs):
             output_spec = kwargs.pop("outputs_list")
             app_callback_manager = kwargs.pop("long_callback_manager", None)
 
@@ -493,7 +499,7 @@ def add_context(*args, **kwargs):
                     return to_json(response)
             else:
                 try:
-                    output_value = _invoke_callback(func, *func_args, **func_kwargs)
+                    output_value = await _invoke_callback(func, *func_args, **func_kwargs)
                 except PreventUpdate as err:
                     raise err
                 except Exception as err:  # pylint: disable=broad-exception-caught

dash/dash.py

@@ -19,6 +19,7 @@
 from typing import Any, Callable, Dict, Optional, Union, List
 
 import flask
+import asyncio
 
 from importlib_metadata import version as _get_distribution_version
 
@@ -191,6 +192,14 @@ def _do_skip(error):
 # Singleton signal to not update an output, alternative to PreventUpdate
 no_update = _callback.NoUpdate()  # pylint: disable=protected-access
 
+async def execute_async_function(func, *args, **kwargs):
+    # Check if the function is a coroutine function
+    if asyncio.iscoroutinefunction(func):
+        return await func(*args, **kwargs)
+    else:
+        # If the function is not a coroutine, call it directly
+        return func(*args, **kwargs)
+
 
 # pylint: disable=too-many-instance-attributes
 # pylint: disable=too-many-arguments, too-many-locals
@@ -1267,7 +1276,7 @@ def long_callback(
         )
 
     # pylint: disable=R0915
-    def dispatch(self):
+    async def dispatch(self):
         body = flask.request.get_json()
 
         g = AttributeDict({})
@@ -1371,19 +1380,27 @@ def dispatch(self):
             raise KeyError(msg) from missing_callback_function
 
         ctx = copy_context()
+        # Create a partial function with the necessary arguments
         # noinspection PyArgumentList
+        partial_func = functools.partial(
+            execute_async_function,
+            func,
+            *args,
+            outputs_list=outputs_list,
+            long_callback_manager=self._background_manager,
+            callback_context=g,
+            app=self,
+            app_on_error=self._on_error,
+        )
+
+        response_data = await ctx.run(partial_func)
+
+        # Check if the response is a coroutine
+        if asyncio.iscoroutine(response_data):
+            response_data = await response_data
+
         response.set_data(
-            ctx.run(
-                functools.partial(
-                    func,
-                    *args,
-                    outputs_list=outputs_list,
-                    long_callback_manager=self._background_manager,
-                    callback_context=g,
-                    app=self,
-                    app_on_error=self._on_error,
-                )
-            )
+            response_data
         )
         return response
 
@@ -2206,7 +2223,7 @@ def router():
                 inputs=inputs,
                 prevent_initial_call=True,
             )
-            def update(pathname_, search_, **states):
+            async def update(pathname_, search_, **states):
                 """
                 Updates dash.page_container layout on page navigation.
                 Updates the stored page title which will trigger the clientside callback to update the app title
@@ -2231,27 +2248,28 @@ def update(pathname_, search_, **states):
                     layout = page.get("layout", "")
                     title = page["title"]
 
-                if callable(layout):
-                    layout = (
-                        layout(**path_variables, **query_parameters, **states)
-                        if path_variables
-                        else layout(**query_parameters, **states)
-                    )
-                if callable(title):
-                    title = title(**path_variables) if path_variables else title()
-
-                return layout, {"title": title}
-
-            _validate.check_for_duplicate_pathnames(_pages.PAGE_REGISTRY)
-            _validate.validate_registry(_pages.PAGE_REGISTRY)
-
-            # Set validation_layout
-            if not self.config.suppress_callback_exceptions:
-                self.validation_layout = html.Div(
-                    [
-                        page["layout"]() if callable(page["layout"]) else page["layout"]
-                        for page in _pages.PAGE_REGISTRY.values()
-                    ]
+                    if callable(layout):
+                        layout = await execute_async_function(layout,
+                                                              **{**(path_variables or {}), **query_parameters, **states}
+                                                              )
+                    if callable(title):
+                        title = await execute_async_function(title,
+                                                             **(path_variables or {})
+                                                             )
+
+                    return layout, {"title": title}
+
+                _validate.check_for_duplicate_pathnames(_pages.PAGE_REGISTRY)
+                _validate.validate_registry(_pages.PAGE_REGISTRY)
+
+                # Set validation_layout
+                if not self.config.suppress_callback_exceptions:
+                    self.validation_layout = html.Div(
+                        [
+                            asyncio.run(execute_async_function(page["layout"])) if callable(page["layout"]) else page[
+                                "layout"]
+                            for page in _pages.PAGE_REGISTRY.values()
+                        ]
                     + [
                         # pylint: disable=not-callable
                         self.layout()