Fix for #770: pip install -U shouldn't look at pypi if not needed

[mbox]

Fix for issue #770: If an exact version is specified for install, and that version is
already installed, then there is no point going to pypi as no install
is needed.

[mbox]

I haven't worked out how to write a testcase for this yet - any pointers welcome. If I figure it out I'll add one.

[pnasrat]

See tests/test_upgrade.py you should be able to do an assert on the result of the second run that no files are created.

[qwcode]

The test isn't whether or not the upgrade writes new files (currently, it's not, so that's not changing), the test would be confirming the package finder is not exercised (after this change). a unit test would be best here that mocks PackageFinder and asserts no calls are made on find_requirements. If I have some time this weekend, I could flesh that out some more if needed.

[msabramo]

So this seems to still be an issue, though you have to turn off pip's caching or clear the cache to see it; otherwise the cache will prevent it from hitting the Internet.

$ pip install --no-cache-dir -U wheel==0.24.0
Retrying (Retry(total=4, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', gaierror(8, 'nodename nor servname provided, or not known'))': /simple/wheel/
Retrying (Retry(total=3, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', gaierror(8, 'nodename nor servname provided, or not known'))': /simple/wheel/
Retrying (Retry(total=2, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', gaierror(8, 'nodename nor servname provided, or not known'))': /simple/wheel/
Retrying (Retry(total=1, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', gaierror(8, 'nodename nor servname provided, or not known'))': /simple/wheel/
Retrying (Retry(total=0, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', gaierror(8, 'nodename nor servname provided, or not known'))': /simple/wheel/
Retrying (Retry(total=4, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', gaierror(8, 'nodename nor servname provided, or not known'))': /simple/wheel/
Retrying (Retry(total=3, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', gaierror(8, 'nodename nor servname provided, or not known'))': /simple/wheel/
Retrying (Retry(total=2, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', gaierror(8, 'nodename nor servname provided, or not known'))': /simple/wheel/
Retrying (Retry(total=1, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', gaierror(8, 'nodename nor servname provided, or not known'))': /simple/wheel/
Retrying (Retry(total=0, connect=None, read=None, redirect=None)) after connection broken by 'ProtocolError('Connection aborted.', gaierror(8, 'nodename nor servname provided, or not known'))': /simple/wheel/
Could not find any downloads that satisfy the requirement wheel==0.24.0 in /Users/marca/python/virtualenvs/pip/lib/python2.7/site-packages
Collecting wheel==0.24.0
  No distributions at all found for wheel==0.24.0 in /Users/marca/python/virtualenvs/pip/lib/python2.7/site-packages

Elapsed time for the above was 15 seconds.

[msabramo]

I would recommend close this and looking at #2493, which merges cleanly.