Issues related to *_by_func methods

[jhakonen]

Hi,

This recent change is making handler_block_by_func to fail for me:
4c39360

I originally encountered this with Tsumiki and reported this in rubiin/Tsumiki#97, but it seems to not reproduce.

I'm getting this error from Tsumiki:

Traceback (most recent call last):
  File "/nix/store/31liyp8gv12nd5dp8wxs4w2cajx57vws-python3-3.13.4-env/lib/python3.13/site-packages/fabric/utils/helpers.py", line 875, in wrapper
    return func(*passed_args[:args_len])
  File "/nix/store/31liyp8gv12nd5dp8wxs4w2cajx57vws-python3-3.13.4-env/lib/python3.13/site-packages/fabric/utils/helpers.py", line 615, in wrapper
    result = func(*args, **kwargs)
  File "/home/jhakonen/code/Tsumiki/modules/osd.py", line 147, in update_volume
    speaker.handler_block_by_func(self.update_volume)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^
TypeError: nothing connected to <bound method AudioOSDContainer.update_volume of <osd.AudioOSDContainer object at 0x7ffff567b380 (modules+osd+AudioOSDContainer at 0x1f352c0)>>

This seems to happen because connect call does not pass the original handler function anymore to the underlying GObject implementation, but instead the handler is a wrapper that is returned from make_arguments_ignorable.
When you then try block the handler like this:

obj.handler_block_by_func(original_handler)

It fails, because the original handler is not there.

I've attached a patch with a unit test that fails with HEAD of main in Fabric:

handler-block-regression.patch.txt

$ git clone https://github.com/Fabric-Development/fabric.git
$ cd fabric

# Checkout commit before the regression, this works fine
$ git checkout 4c39360^
...
HEAD is now at 49c00af feat: implement more overrides for `Service`

$ git apply /path/to/handler-block-regression.patch
$ nix develop --command bash -c "python3 tests/service.3.py"
............
----------------------------------------------------------------------
Ran 12 tests in 0.001s

OK

$ git checkout .

# Checkout main, or the failing 4c39360 commit, or any commit in between
$ git checkout main
$ git apply /path/to/handler-block-regression.patch
$ nix develop --command bash -c "python3 tests/service.3.py"
...........E...
======================================================================
ERROR: testServiceSignalsConnectAndEmit8 (__main__.TestServiceSignals.testServiceSignalsConnectAndEmit8)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/jhakonen/code/fabric/tests/service.3.py", line 318, in testServiceSignalsConnectAndEmit8
    service.handler_block_by_func(handler)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
TypeError: nothing connected to <function TestServiceSignals.testServiceSignalsConnectAndEmit8.<locals>.handler at 0x7ffff180d300>

----------------------------------------------------------------------
Ran 15 tests in 0.002s

FAILED (errors=1)

[its-darsh]

This points to a whole class of issues. Issues related to *_by_func functions and methods (usually those related to connection and disconnection.)

Thanks for the detailed description. I'll need to illustrate a fix for this (maybe keep track of connections locally, however that's expensive.)

For now, I'd recommend you set the ignore_missing keyword argument to False when creating a connection to a function that you're going to reference later.