Commit 8a649631 authored by Xavier Thompson's avatar Xavier Thompson

[fix] Use only ws.find in install

Replace `pkg_resources.Environment(ws.entries).best_match(req, ws)`
with `ws.find(req)`.

The first already starts by calling `ws.find(req)` to attempt to find
an already activated dist in the working set, but if none is found it
then proceeds to scan through the entries of the environment - i.e.
the locations of the directly-requested distributions, `ws.entries` -
to activate a dist at these locations if one matches.

This is problematic when directly-requested distributions are found in
a location shared by multiple dists, such as site-packages: this gives
that location precedence over the normal order of locations scanned by
easy_install, and can result in undesired versions being chosen over
versions available in ./eggs or in ./develop-eggs. The random aspect
of this is also problematic, as the order of paths considered will
depend on the order of the directly-requested distributions and where
they are found.
parent 0dcfd8c2
......@@ -706,10 +706,6 @@ class Installer(object):
requirements.reverse() # Set up the stack.
processed = {} # This is a set of processed requirements.
best = {} # This is a mapping of package name -> dist.
# Note that we don't use the existing environment, because we want
# to look for new eggs unless what we have is the best that
# matches the requirement.
env = pkg_resources.Environment(ws.entries)
while requirements:
# Process dependencies breadth-first.
......@@ -721,7 +717,15 @@ class Installer(object):
dist = best.get(req.key)
if dist is None:
try:
dist = env.best_match(req, ws)
# Note that we first attempt to find an already active dist
# in the working set. This will detect version conflicts.
# XXX We expressly avoid activating dists in the entries of
# the current working set: they might not reflect the order
# of the environment. This is not so bad when the versions
# are pinned, but when calling install(['zc.buildout']), it
# can come up with completely different dists than the ones
# currently running.
dist = ws.find(req)
except pkg_resources.VersionConflict as err:
logger.debug(
"Version conflict while processing requirement %s "
......
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