[WIP] Add hooks #3029
[WIP] Add hooks #3029
Conversation
T4rk1n
requested review from
alexcjohnson,
ndrezn,
gvwilson and
emilykl
as code owners
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| def layout(func): | ||
| """ | ||
| Run a function when serving the layout, the return value |
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This looks like it saves the function func but doesn't run it - is the comment incorrect?
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No, it is only run when serving the layout, the docstring are placeholder, we can improve the wording.
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| def wrap(func): | ||
| _name = name or func.__name__ | ||
| _ns["routes"].append((_name, func, methods)) |
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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"?
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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.
| return wrap | ||
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| def error(func: _t.Callable[[Exception], _t.Any]): |
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you're declaring the type of func here but you don't declare types in the previous registration functions - declare them all for consistency?
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There is some issue with cyclic dependencies with the other types, I'll see what I can do.
| """ | ||
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| def wrap(func): | ||
| _ns["callback"].append((list(args), dict(kwargs), func)) |
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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.
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| class HooksManager: | ||
| _registered = False |
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please add a comment explaining what _registered is for - in particular, why is it a class-level variable instead of an instance variable?
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| for dist in importlib.metadata.distributions(): | ||
| for entry in dist.entry_points: | ||
| if entry.group != "dash": |
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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.
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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.
| @@ -573,6 +573,8 @@ def __init__( # pylint: disable=too-many-statements | |||
| for plugin in plugins: | |||
| plugin.plug(self) | |||
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| self._setup_hooks() | |||
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| # tracks internally if a function already handled at least one request. | |||
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Yes, it's the setup that load the plugins and add the setup/callback/error hooks.
| self._hooks = HooksManager | ||
| self._hooks.register_setuptools() | ||
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| for setup in self._hooks.get_hooks("setup"): |
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is this where the difference in structure between the things that are stored in different _ns entries shows up? this loop is getting one value per list item; the loop below is getting three.
Add
dash.hookssystem to enhance created apps with functionality. These hooks can be automatically added to apps without imports by adding adashentry toentry_pointsinsetup.py.Hooks:
layout: wraps the layout before serving. Take the layout as first argument and the return value is used as the new layout.setup: Called when aDash.__init__is called, used to get a reference to the app.callback: Add a callback to all the apps. Same signature asdash.callback.route: Add a route to the flask server, the route will be prefixed withroutes_pathname_prefix.error: Add a global error handler to be used with callbacks.