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mercurial: implement import hook for handling C/Python modules...
mercurial: implement import hook for handling C/Python modules There are a handful of modules that have both pure Python and C extension implementations. Currently, setup.py copies files from mercurial/pure/*.py to mercurial/ during the install process if C extensions are not available. This way, "import mercurial.X" will work whether C extensions are available or not. This approach has a few drawbacks. First, there aren't run-time checks verifying the C extensions are loaded when they should be. This could lead to accidental use of the slower pure Python modules. Second, the C extensions aren't compatible with PyPy and running Mercurial with PyPy requires installing Mercurial - you can't run ./hg from a source checkout. This makes developing while running PyPy somewhat difficult. This patch implements a PEP-302 import hook for finding and loading the modules with both C and Python implementations. When a module with dual implementations is requested for import, its import is handled by our import hook. The importer has a mechanism that controls what types of modules we allow to load. We call this loading behavior the "module load policy." There are 3 settings: * Only load C extensions * Only load pure Python * Try to load C and fall back to Python An environment variable allows overriding this policy at run time. This is mainly useful for developers and for performing actions against the source checkout (such as installing), which require overriding the default (strict) policy about requiring C extensions. The default mode for now is to allow both. This isn't proper and is technically backwards incompatible. However, it is necessary to implement a sane patch series that doesn't break the world during future bisections. The behavior will be corrected in future patch. We choose the main mercurial/__init__.py module for this code out of necessity: in a future world, if the custom module importer isn't registered, we'll fail to find/import certain modules when running from a pure installation. Without the magical import-time side-effects, *any* importer of mercurial.* modules would be required to call a function to register our importer. I'm not a fan of import time side effects and I initially attempted to do this. However, I was foiled by our own test harness, which has numerous `python` invoked scripts that "import mercurial" and fail because the importer isn't registered. Realizing this problem is probably present in random Python scripts that have been written over the years, I decided that sacrificing purity for backwards compatibility is necessary. Plus, if you are programming Python, "import" should probably "just work." It's worth noting that now that we have a custom module loader, it would be possible to hook up demand module proxies at this level instead of replacing __import__. We leave this work for another time, if it's even desired. This patch breaks importing in environments where Mercurial modules are loaded from a zip file (such as py2exe distributions). This will be addressed in a subsequent patch.

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filesets.txt
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Matt Mackall
fileset: add a help topic...
r14686 Mercurial supports a functional language for selecting a set of
Mads Kiilerich
check-code: check txt files for trailing whitespace
r18960 files.
Matt Mackall
fileset: add a help topic...
r14686
Like other file patterns, this pattern type is indicated by a prefix,
'set:'. The language supports a number of predicates which are joined
by infix operators. Parenthesis can be used for grouping.
Identifiers such as filenames or patterns must be quoted with single
or double quotes if they contain characters outside of
``[.*{}[]?/\_a-zA-Z0-9\x80-\xff]`` or if they match one of the
predefined predicates. This generally applies to file patterns other
than globs and arguments for predicates.
Special characters can be used in quoted identifiers by escaping them,
e.g., ``\n`` is interpreted as a newline. To prevent them from being
interpreted, strings can be prefixed with ``r``, e.g. ``r'...'``.
There is a single prefix operator:
``not x``
Files not in x. Short form is ``! x``.
These are the supported infix operators:
``x and y``
The intersection of files in x and y. Short form is ``x & y``.
``x or y``
The union of files in x and y. There are two alternative short
forms: ``x | y`` and ``x + y``.
``x - y``
Files in x but not in y.
The following predicates are supported:
.. predicatesmarker
Some sample queries:
- Show status of files that appear to be binary in the working directory::
hg status -A "set:binary()"
- Forget files that are in .hgignore but are already tracked::
hg forget "set:hgignore() and not ignored()"
- Find text files that contain a string::
FUJIWARA Katsunori
help: use "hg files" instead of "hg locate" in "hg help filesets"...
r23109 hg files "set:grep(magic) and not binary()"
Matt Mackall
fileset: add a help topic...
r14686
- Find C files in a non-standard encoding::
FUJIWARA Katsunori
help: use "hg files" instead of "hg locate" in "hg help filesets"...
r23109 hg files "set:**.c and not encoding('UTF-8')"
Matt Mackall
fileset: add a help topic...
r14686
- Revert copies of large binary files::
hg revert "set:copied() and binary() and size('>1M')"
Arne Babenhauserheide
help: fileset foo.lst was named files.lst
r14829 - Remove files listed in foo.lst that contain the letter a or b::
Matt Mackall
fileset: add a help topic...
r14686
hg remove "set: 'listfile:foo.lst' and (**a* or **b*)"
See also :hg:`help patterns`.