[PATCH 3 of 3 v3] demandimport: reject contextlib._GeneratorContextManager on Py < 3.2

Siddharth Agarwal sid at less-broken.com
Wed Sep 21 15:23:08 EDT 2016


On 9/21/16 12:09, timeless wrote:
> # HG changeset patch
> # User timeless <timeless at mozdev.org>
> # Date 1474429683 0
> #      Wed Sep 21 03:48:03 2016 +0000
> # Node ID 0070696439eab002f6dd32bcb40eb671daff800a
> # Parent  adb54fd7d90f0ca607432ed7ae884da55ec427de
> # Available At https://bitbucket.org/timeless/mercurial-crew
> #              hg pull https://bitbucket.org/timeless/mercurial-crew -r 0070696439ea
> demandimport: reject contextlib._GeneratorContextManager on Py < 3.2

As a general thing I don't think we should be spending time trying to 
fix this implementation of demandimport on Python 3 at all. I would much 
rather we use an implementation based on the new importlib stuff, like 
the one I sent to the list a while back. (Hopefully I can get it in 
during the sprint.)

- Siddharth

>
> decorator expects:
>   from contextlib import _GeneratorContextManager
> to throw an exception on python < 3.2 (issue5373).
>
> We tell demandimport to throw it.
>
> diff -r adb54fd7d90f -r 0070696439ea mercurial/demandimport.py
> --- a/mercurial/demandimport.py	Wed Sep 21 18:58:54 2016 +0000
> +++ b/mercurial/demandimport.py	Wed Sep 21 03:48:03 2016 +0000
> @@ -313,6 +313,12 @@
>   if os.name != 'nt':
>       reject('distutils', 'msvc9compiler', ImportError, 'No module named _winreg')
>   
> +# decorator imported by ipython from pygments does an import which isn't
> +# friendly to demandimport.
> +if sys.version_info[0] < 3 or sys.version_info[1] < 2:
> +    reject('contextlib', '_GeneratorContextManager',
> +           ImportError, 'cannot import name _GeneratorContextManager')
> +
>   def isenabled():
>       return builtins.__import__ == _demandimport
>   
> diff -r adb54fd7d90f -r 0070696439ea tests/test-demandimport.py
> --- a/tests/test-demandimport.py	Wed Sep 21 18:58:54 2016 +0000
> +++ b/tests/test-demandimport.py	Wed Sep 21 03:48:03 2016 +0000
> @@ -71,6 +71,15 @@
>   except ImportError:
>       pass
>   
> +if sys.version_info[0] < 3 or sys.version_info[1] < 2:
> +    try:
> +        from contextlib import _GeneratorContextManager
> +        print('contextlib._GeneratorContextManager needs to be an '
> +              'immediate importerror on python <3.2')
> +        _GeneratorContextManager.__doc__
> +    except ImportError:
> +        pass
> +
>   demandimport.disable()
>   os.environ['HGDEMANDIMPORT'] = 'disable'
>   # this enable call should not actually enable demandimport!
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