Hello, I think there is a problem with Python 2.7: I installed it, and tried to compile GObject-Introspection 0.9.2. Here is the result:

...
  GISCAN GLib-2.0.gir
Traceback (most recent call last):
  File "../tools/g-ir-scanner", line 36, in <module>
    from giscanner.scannermain import scanner_main
  File "/sources/gobject-introspection-0.9.2/giscanner/scannermain.py", line 31, in <module>
    from giscanner.dumper import compile_introspection_binary
  File "/sources/gobject-introspection-0.9.2/giscanner/dumper.py", line 26, in <module>
    from .glibtransformer import IntrospectionBinary
  File "/sources/gobject-introspection-0.9.2/giscanner/glibtransformer.py", line 34, in <module>
    from .transformer import Names
  File "/sources/gobject-introspection-0.9.2/giscanner/transformer.py", line 31, in <module>
    from .girparser import GIRParser
  File "/sources/gobject-introspection-0.9.2/giscanner/girparser.py", line 32, in <module>
    from .girwriter import COMPATIBLE_GIR_VERSION
  File "/sources/gobject-introspection-0.9.2/giscanner/girwriter.py", line 30, in <module>
    from .xmlwriter import XMLWriter
  File "/sources/gobject-introspection-0.9.2/giscanner/xmlwriter.py", line 70, in <module>
    with LibtoolImporter:
AttributeError: __exit__

Oops, no GObject-Introspection for me. Investigating the bug, I looked in the recent changes in Python2.7 for something interesting, and found this: 
A new opcode was added to perform the initial setup for with statements, looking up the __enter__()  and __exit__()  methods. (Contributed by Benjamin Peterson.)

Finally, I made 3 test cases to the bug. All 3 produce no input in Python 2.6, but crash pretty nicely in 2.7, the first 2 not finding __exit__ and the last missing __enter__.

I will try to make a patch, however my CPython skills are not so great, so you will probably make a better one.

Thank you for the report. Unfortunately, the 2.6 behavior was a bug, as I explained on #9220: Magic methods are looked up on the object’s class, not in the object’s __dict__. <http://docs.python.org/reference/datamodel#specialnames>

(Your test with class methods was a clever idea, but a class is a type instance, so it’s the same behavior: __enter__ is looked up on type, not on the class. Nice try :)

Tip for future bug reports: We prefer regular files over archives. Thanks again!

Bug or not bug, Python2.7 breaks Gobject-Introspection.

Please produce a test to prove that Python behaves in contradiction to the documentation. Otherwise I’m afraid it’s a GI bug, like in your tests :)

My test on Class Methods was based on the GI Code that does not run on Python 2.7.

I am afraid we have conflicting viewpoints. You are saying that upgrading Python broke code, and I agree it’s a bad thing. Usually such regression reports are accepted and fixed.

In this case however, the code was already broken in the previous version, it was only working because of a problem in the implementation. So from the viewpoint of GI users, it’s a regression, but from the viewpoint of Python the 2.7 behavior fixes a regression in 2.6. It is not supported to find magic methods (“__name__”) on instances.

Since Benjamin Peterson, release manager for 2.7, confirmed that the change was intentional, I’m closing again.

To solve the bug in GI, you need to define a metaclass with those __enter__ and __exit__ methods, then use it as metaclass for LibtoolImporter. Please send me private email if you want more details.

Done it for myself. However, I am not a GI Maintainer - you should talk with them and send them this patch.

Since you know the project, the bug and the fix, I think you’re in a better position than me to talk with them.