tests/test-atomictempfile.py

completion: add a debugpathcomplete command

The bash_completion code uses "hg status" to generate a list of
possible completions for commands that operate on files in the
working directory. In a large working directory, this can result
in a single tab-completion being very slow (several seconds) as a
result of checking the status of every file, even when there is no
need to check status or no possible matches.

The new debugpathcomplete command gains performance in a few simple
ways:

* Allow completion to operate on just a single directory. When used
  to complete the right commands, this considerably reduces the
  number of completions returned, at no loss in functionality.

* Never check the status of files. For completions that really must
  know if a file is modified, it is faster to use status:

  hg status -nm 'glob:myprefix**'

Performance:

Here are the commands used by bash_completion to complete, run in
the root of the mozilla-central working dir (~77,000 files) and
another repo (~165,000 files):

All "normal state" files (used by e.g. remove, revert):

                            mozilla    other
  status -nmcd 'glob:**'       1.77     4.10 sec
  debugpathcomplete -f -n      0.53     1.26
  debugpathcomplete -n         0.17     0.41

("-f" means "complete full paths", rather than the current directory)

Tracked files matching "a":

                            mozilla    other
  status -nmcd 'glob:a**'      0.26     0.47
  debugpathcomplete -f -n a    0.10     0.24
  debugpathcomplete -n a       0.10     0.22

We should be able to further improve completion performance once
the critbit work lands. Right now, our performance is limited by
the need to iterate over all keys in the dirstate.

import os
import glob
import unittest
import silenttestrunner

from mercurial.util import atomictempfile

class testatomictempfile(unittest.TestCase):
    def test1_simple(self):
        if os.path.exists('foo'):
            os.remove('foo')
        file = atomictempfile('foo')
        (dir, basename) = os.path.split(file._tempname)
        self.assertFalse(os.path.isfile('foo'))
        self.assertTrue(basename in glob.glob('.foo-*'))

        file.write('argh\n')
        file.close()

        self.assertTrue(os.path.isfile('foo'))
        self.assertTrue(basename not in glob.glob('.foo-*'))

    # discard() removes the temp file without making the write permanent
    def test2_discard(self):
        if os.path.exists('foo'):
            os.remove('foo')
        file = atomictempfile('foo')
        (dir, basename) = os.path.split(file._tempname)

        file.write('yo\n')
        file.discard()

        self.assertFalse(os.path.isfile('foo'))
        self.assertTrue(basename not in os.listdir('.'))

    # if a programmer screws up and passes bad args to atomictempfile, they
    # get a plain ordinary TypeError, not infinite recursion
    def test3_oops(self):
        self.assertRaises(TypeError, atomictempfile)

if __name__ == '__main__':
    silenttestrunner.main(__name__)