Add hooks #3029

T4rk1n · 2024-10-08T17:59:51Z

Add dash.hooks system to enhance created apps with functionality. These hooks can be automatically added to apps without imports by adding a dash entry to entry_points in setup.py.

Hooks:

layout: wraps the layout before serving. Take the layout as first argument and the return value is used as the new layout.

from dash  import hooks, html

@hooks.layout
def hook_layout(layout):
  return [html.Div("hooked")] + layout

setup: Called when a Dash.__init__ is called, used to get a reference to the app.
callback: Add a callback to all the apps. Same signature as dash.callback.
route: Add a route to the flask server, the route will be prefixed with routes_pathname_prefix.
error: Add a global error handler to be used with callbacks.

gvwilson

some questions - happy to chat

gvwilson · 2024-10-09T12:41:11Z

dash/_hooks.py

+
+def layout(func):
+    """
+    Run a function when serving the layout, the return value


This looks like it saves the function func but doesn't run it - is the comment incorrect?

No, it is only run when serving the layout, the docstring are placeholder, we can improve the wording.

gvwilson · 2024-10-09T12:41:54Z

dash/_hooks.py

+
+    def wrap(func):
+        _name = name or func.__name__
+        _ns["routes"].append((_name, func, methods))


hm - so some of the _ns entries are functions and some are tuples, so the structure of entries in _ns["key"] depends on the value of "key"?

The _ns just saves the info for the different hooks, it isn't meant for public usage. For routes/callbacks it needs more arguments so it's saved in a tuple for easy unpacking.

gvwilson · 2024-10-09T12:42:24Z

dash/_hooks.py

+    return wrap
+
+
+def error(func: _t.Callable[[Exception], _t.Any]):


you're declaring the type of func here but you don't declare types in the previous registration functions - declare them all for consistency?

There is some issue with cyclic dependencies with the other types, I'll see what I can do.

gvwilson · 2024-10-09T12:43:40Z

dash/_hooks.py

+    """
+
+    def wrap(func):
+        _ns["callback"].append((list(args), dict(kwargs), func))


again, it looks like the structure of values stored in _ns depends on the key, which feels like it should be documented somewhere in this file to help the next person reading the code.

gvwilson · 2024-10-09T12:44:20Z

dash/_hooks.py

+
+
+class HooksManager:
+    _registered = False


please add a comment explaining what _registered is for - in particular, why is it a class-level variable instead of an instance variable?

dash/_hooks.py

gvwilson · 2024-10-09T12:45:25Z

dash/_hooks.py

+
+        for dist in importlib.metadata.distributions():
+            for entry in dist.entry_points:
+                if entry.group != "dash":


hm - hard-coded string embedded in the file - define as a constant at the top of the file to make it easier to find? and a comment here explaining what this filtering is doing would be welcome - I don't really understand it.

This just a filter on the entry_points of a setup.py, the entry_points are used to add cli and other functionalities to python packages. I usually don't define a variable if it's only used one time.

dash/dash.py

…ources.

dash/_hooks.py

gvwilson

a few questions for my own curiosity but I think this is ready to merge

gvwilson · 2024-10-28T18:05:30Z

dash/_hooks.py

@@ -0,0 +1,222 @@
+import typing as _t


just curious: why this rather than importing the specific things you need from typing (e.g., from typing import TypeVar)?

gvwilson · 2024-10-28T18:06:58Z

dash/_hooks.py

+
+
+# pylint: disable=too-few-public-methods
+class _Hook(_tx.Generic[HookDataType]):


docstrings? or do we not document internal classes like this?

gvwilson · 2024-10-28T18:08:21Z

dash/_hooks.py

+            "callback": [],
+            "index": [],
+        }
+        self._js_dist = []


what is _dist short for?

gvwilson · 2024-10-28T18:08:45Z

dash/_hooks.py

+        self._finals = {}
+
+    def add_hook(
+        self, hook: str, func: _t.Callable, priority=None, final=False, data=None


no types for priority, final, and data?

gvwilson · 2024-10-28T18:10:43Z

dash/_hooks.py

+        self._ns[hook] = sorted(hks, reverse=True, key=lambda h: h.priority)
+
+    def get_hooks(self, hook: str) -> _t.List[_Hook]:
+        final = self._finals.get(hook, None)


is this just to ensure that final is the last hook in this list? if so, maybe a comment to that effect?

gvwilson · 2024-10-28T18:13:05Z

dash/_hooks.py

+        """Add stylesheets to the page."""
+        self._css_dist.extend(distribution)
+
+    def index(self, priority=None, final=False):


I don't know what "the index" means in this context?

The index is the raw html of the served dash index (like index.html served for '/').

gvwilson · 2024-10-28T18:13:18Z

dash/_hooks.py

+
+
+class HooksManager:
+    _registered = False


gvwilson · 2024-10-28T18:14:13Z

dash/dash.py

+            args,
+            kwargs,
+        ) in self._hooks.hooks._clientside_callbacks:
+            _callback.register_clientside_callback(


nice and clean

gvwilson · 2024-10-28T18:49:48Z

dash/resources.py

+    "ResourceType",
+    {
+        "namespace": str,
+        "async": _t.Union[bool, _t.Literal["eager", "lazy"]],


so legal values are True, False, "eager", and "lazy"? Are these documented somewhere?

Yes those are the valid values, along with None/undefined for all of them properties since total=False set them as optional.
This is mostly for usage of async chunks of components libraries (dcc.Graph, dcc.Markdown, dash_table.DataTable). The usual value is True or undefined, eager or lazy are abstractions that are not very well documented, it is commented here:

dash/dash/resources.py

Lines 66 to 72 in d26c9d3

# Async assigns a value dynamically to 'dynamic'

# based on the value of 'async' and config.eager_loading

#

# True -> dynamic if the server is not eager, False otherwise

# 'lazy' -> always dynamic

# 'eager' -> dynamic if server is not eager

# (to prevent ever loading it)

With Dash(eager_loading=True), the async: "eager" chunks normally loaded when the component mounts, would be loaded on page load.

gvwilson · 2024-10-28T18:50:34Z

tests/integration/test_hooks.py

@@ -0,0 +1,188 @@
+from flask import jsonify


Add hooks

54d338d

T4rk1n added the dash-3.0 Going in dash-3.0 release. label Oct 8, 2024

T4rk1n requested review from alexcjohnson, ndrezn, gvwilson and emilykl as code owners October 8, 2024 17:59

Add hook cleanup for tests.

1b4d1a3

gvwilson reviewed Oct 9, 2024

View reviewed changes

T4rk1n added 2 commits October 9, 2024 10:17

Add more typing to hooks

8b68e62

yield before tests hook cleanup fixture

fde59e8

gvwilson assigned T4rk1n Oct 9, 2024

gvwilson added feature something new P1 needed for current cycle labels Oct 9, 2024

T4rk1n mentioned this pull request Oct 16, 2024

Undeprecate plugins #3039

Merged

T4rk1n added 8 commits October 21, 2024 15:51

Add priority and final keyword to hooks.

59234db

Set cblb001 flaky

89d6a93

Set entrypoint group to dash-hooks

d405c72

Add hooks for index modification and adding script and stylesheet res…

d26c9d3

…ources.

Reset hooks dist on cleanup

ee1ddea

Fix test async resources.

d69a87c

reset final hooks

bd1c8f2

disable too-many-ancestors broken pylint rule

d3d88c1

LiamConnors reviewed Oct 25, 2024

View reviewed changes

dash/_hooks.py Outdated Show resolved Hide resolved

add clientside callback hook

998171a

T4rk1n changed the title ~~[WIP] Add hooks~~ Add hooks Oct 28, 2024

gvwilson approved these changes Oct 28, 2024

View reviewed changes

T4rk1n added 2 commits October 29, 2024 10:01

Add more typing/comments to hooks.

b405e1b

Merge branch 'dash-3.0' into feat/hooks

7e2f37e

T4rk1n merged commit 5fe20c7 into dash-3.0 Nov 8, 2024
3 checks passed

T4rk1n deleted the feat/hooks branch November 8, 2024 16:48

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		return wrap


		def error(func: _t.Callable[[Exception], _t.Any]):



		# pylint: disable=too-few-public-methods
		class _Hook(_tx.Generic[HookDataType]):

	# Async assigns a value dynamically to 'dynamic'
	# based on the value of 'async' and config.eager_loading
	#
	# True -> dynamic if the server is not eager, False otherwise
	# 'lazy' -> always dynamic
	# 'eager' -> dynamic if server is not eager
	# (to prevent ever loading it)

Add hooks #3029

Add hooks #3029

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T4rk1n commented Oct 8, 2024

Hooks:

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