Django runserver doesn't reload itself after updating files on disk that raised error on import.

[Yuri Baburov]

When autoreload is on,

1. after any occasional error in any models.py file, reloading doesn't work for further updates of that file.
2. modules that had import errors and updated on disk, are never reloaded.

Applied patch fixes the described problems and also allows to track various wrong usages of import API.

[Yuri Baburov]

Fix

[Malcolm Tredinnick]

I'm -1 on this because changing the behaviour of __import__ for everything just for a couple of edge-cases with the auto-reloader doesn't seem worth it. But we can make an ultimate decision after 1.0.

[Yuri Baburov]

The patch will be rewritten to new hooks from PEP 302 today, it won't include import overriding.
Please don't judge without knowing all facts.

[Yuri Baburov]

Well, actually, you were absolutely correct in previous comment. Adding new hook that doesn't deal with import in any way, so it's safe to use.

[Yuri Baburov]

Better fix working through PEP 302

[(none)]

Milestone post-1.0 deleted

[Yuri Baburov]

Latest patch is at ​http://github.com/buriy/django/commit/295d0c15135d6de08f79ccd68be13713a17faa96

[Aymeric Augustin]

Accepting the patch because the submitter addressed Malcolm's comment.

Unfortunately the GitHub link is broken, and the previous patch needs updating — at least, we no longer need Python 2.3 compatibility.

[Aymeric Augustin]

This problem was also reported in #9589. This ticket has patches but their approach was rejected by a core dev and a BDFL.

[Carl Meyer]

Replying to aaugustin:

This problem was also reported in #9589. This ticket has patches but their approach was rejected by a core dev and a BDFL.

I don't think that's accurate - the initial patch there was rejected (for good reason), but there are two subsequent patches that take quite a different (and, at least at first glance, much better) approach; there's no evidence those patches were ever given review. I think the second two patches on #9859 deserve another look if someone does look into fixing this.

[Aymeric Augustin]

Indeed, Carl is right. Whoever tackles this should review both tickets.

[ebas]

After reviewing all the patches, i came up with this patch against the 1.4.x branch:
​https://github.com/ebas/django/commit/970cee879c84eb495f385822e4e9c99f2aed2088

Its based on a patch found in this post:
​https://groups.google.com/forum/?fromgroups=#!topic/django-developers/rJkUEGdMGV0

The patch consists of the top commits on this branch:
​https://github.com/rca/django/commits/master/django/utils/autoreload.py

Just to be complete, the noteworthy other patches from both #9589 and #8413:

• attachment:autoreload-error_decorator-r11628.patch:ticket:9589​
• ​https://github.com/buriy/django/commit/7c2c45ed24012d23d0c656c16d53efb8a22846c1#django/utils/autoreload.py

[tdhutt@…]

This is really annoying. I briefly tested ebas's patch and it seems to work. Can somebody please apply it?

[tdhutt@…]

PS: Here is the patch, since apparently github doesn't let you download them. Tested on django 1.4.1. The relavent file is in (usually) in /usr/local/lib/python2.7/dist-packages/django/utils/autoreload.py so you can apply it like this:

cd /usr/local/lib/python2.7/dist-packages/django/utils/autoreload.py
sudo patch autoreload.py ~/autoreload_patch.diff

where autoreload_patch.diff contains the following:

53a54

_error_files = []

57c58
< for filename in filter(lambda v: v, map(lambda m: getattr(m, "file", None), sys.modules.values())):
---

for filename in filter(lambda v: v, map(lambda m: getattr(m, "file", None), sys.modules.values())) + _error_files:

72a74,76

try:

del _error_files[_error_files.index(filename)]

except ValueError: pass

75a80,92

def check_errors(fn):

def wrapper(*args, kwargs):

try:

fn(*args, kwargs)

except (ImportError, IndentationError, NameError,

SyntaxError, TypeError), msg:

et, ev, tb = sys.exc_info()
if ev.filename not in _error_files:

_error_files.append(ev.filename)

raise

return wrapper

144,145c161,162
< reloader(main_func, args, kwargs)
<
---

wrapped_main_func = check_errors(main_func)
reloader(wrapped_main_func, args, kwargs)

[anonymous]

Damnit. Try again:

53a54
> _error_files = []
57c58
<     for filename in filter(lambda v: v, map(lambda m: getattr(m, "__file__", None), sys.modules.values())):
---
>     for filename in filter(lambda v: v, map(lambda m: getattr(m, "__file__", None), sys.modules.values())) + _error_files:
72a74,76
>             try:
>                 del _error_files[_error_files.index(filename)]
>             except ValueError: pass
75a80,92
> def check_errors(fn):
>     def wrapper(*args, **kwargs):
>         try:
>             fn(*args, **kwargs)
>         except (ImportError, IndentationError, NameError, 
>                 SyntaxError, TypeError), msg:
>             et, ev, tb = sys.exc_info()
>             if ev.filename not in _error_files:
>                 _error_files.append(ev.filename)
> 
>             raise
>     return wrapper
> 
144,145c161,162
<     reloader(main_func, args, kwargs)
< 
---
>     wrapped_main_func = check_errors(main_func)
>     reloader(wrapped_main_func, args, kwargs)

[tdhutt@…]

After more extensive testing, it's working quite well but I did get this one error:

Unhandled exception in thread started by <function wrapper at 0x1f6e8c0>
Error in sys.excepthook:
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 50, in apport_excepthook
    if not enabled():
TypeError: 'NoneType' object is not callable

Original exception was:
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/django/utils/autoreload.py", line 83, in wrapper
    fn(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/runserver.py", line 111, in inner_run
    ipv6=self.use_ipv6, threading=threading)
  File "/usr/local/lib/python2.7/dist-packages/django/core/servers/basehttp.py", line 253, in run
    httpd.serve_forever()
  File "/usr/lib/python2.7/SocketServer.py", line 225, in serve_forever
    r, w, e = select.select([self], [], [], poll_interval)
AttributeError: 'NoneType' object has no attribute 'select'

[Ramiro Morales]

I've updated the patch contributed by berto to #9589: ​https://github.com/ramiro/django/compare/8413_9589_reload_runserver

Testing of the patch on Unixy platforms (including Mac OS X) is welcome. I will try to test it on Windows.

I plan to commit this to master in a few days.

[Tim Graham]

Closing as duplicate of #9589 - it looks like the fix was committed with a reference to that ticket but not this one so it wasn't closed automatically.