[docs] [issue25500] _find_and_load_unlocked doesn't always use __import__

[Sergei Lebedev]

New submission from Sergei Lebedev:

According to the current import system documentation

> When calling ``__import__()`` as part of an import statement, the import system first checks the module global namespace for a function by that name. If it is not found, then the standard builtin ``__import__()`` is called.

However, one can easily verify this isn't (always) the case::

    import sys

    assert "glob" not in sys.modules
    __import__ = print
   
    import glob  # Doesn't print anything.

I've traced the import statement from ``ceval.c`` to the frozen ``importlib._bootstrap`` and it seems the cause of the problem is in ``_find_and_load_unlocked``, which simply ignores the ``_import`` argument in the case above::

    def _find_and_load_unlocked(name, import_):
        path = None
        # ... parent processing ...
        spec = _find_spec(name, path)
        if spec is None:
            raise ImportError(_ERR_MSG.format(name), name=name)
        else:
            # XXX import_ is not used.
            module = _SpecMethods(spec)._load_unlocked()
        # ... more parent processing ...
        return module

I'm not sure if this is a bug in the documentation or implementation, so any feedback is appreciated.

----------
assignee: docs at python
components: Documentation, Library (Lib)
messages: 253635
nosy: docs at python, superbobry
priority: normal
severity: normal
status: open
title: _find_and_load_unlocked doesn't always use __import__
versions: Python 3.4, Python 3.5

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue25500>
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