#23641: Apps.set_installed_apps causes signals registered with apps as senders
not
to be received
------------------------------+------------------------------------
Reporter: wrwrwr | Owner: nobody
Type: Bug | Status: closed
Component: Core (Other) | Version: master
Severity: Normal | Resolution: fixed
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by timgraham):
Putting the original commit message here for posterity:
{{{
In the case of the sites app, this solves a problem appearing when
Apps.set_installed_apps() (override/modify_settings) is used before
sending the post_migrate signal -- create_default_site() handler is
not executed in such a case.
To elaborate a bit, the signal is connected with the sender attribute
equal to an AppConfig instance; the signal dispatcher stores its id to
identify the sender that we're interested in receiving signals from.
The set_installed_apps() method reinstantiates all AppConfigs, and
when the migration machinery emits signals using these new app configs
as senders, their ids don't match those stored by the dispatcher.
Handlers registered before overriding installed apps are not called.
Moving signal registration to ready() ensures that signals that use
an app config as a sender will be connected for any new instance.
On the other hand, the ready() method may be executed more than once
during testing, so signals that expect other senders may need to be
protected from double registration.
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/23641#comment:15>
Django <https://code.djangoproject.com/>
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