Mercurial > hg
annotate mercurial/txnutil.py @ 31553:56acc4250900
scmutil: add a simple key-value file helper
The purpose of the added class is to serve purposes like save files of shelve
or state files of shelve, rebase and histedit. Keys of these files can be
alphanumeric and start with letters, while values must not contain newlines.
In light of Mercurial's reluctancy to use Python's json module, this tries
to provide a reasonable alternative for a non-nested named data.
Comparing to current approach of storing state in plain text files, where
semantic meaning of lines of text is only determined by their oreder,
simple key-value file allows for reordering lines and thus helps handle
optional values.
Initial use-case I see for this is obs-shelve's shelve files. Later we
can possibly migrate state files to this approach.
The test is in a new file beause I did not figure out where to put it
within existing test suite. If you give me a better idea, I will gladly
follow it.
author | Kostia Balytskyi <ikostia@fb.com> |
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date | Fri, 10 Mar 2017 14:33:42 -0800 |
parents | 206532700213 |
children | 2372284d9457 |
rev | line source |
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31050
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1 # txnutil.py - transaction related utilities |
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2 # |
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3 # Copyright FUJIWARA Katsunori <foozy@lares.dti.ne.jp> and others |
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4 # |
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5 # This software may be used and distributed according to the terms of the |
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6 # GNU General Public License version 2 or any later version. |
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7 |
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8 from __future__ import absolute_import |
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9 |
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10 import errno |
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11 |
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12 from . import ( |
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13 encoding, |
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14 ) |
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15 |
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16 def mayhavepending(root): |
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17 '''return whether 'root' may have pending changes, which are |
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18 visible to this process. |
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19 ''' |
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20 return root == encoding.environ.get('HG_PENDING') |
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21 |
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22 def trypending(root, vfs, filename, **kwargs): |
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23 '''Open file to be read according to HG_PENDING environment variable |
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24 |
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25 This opens '.pending' of specified 'filename' only when HG_PENDING |
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26 is equal to 'root'. |
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27 |
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28 This returns '(fp, is_pending_opened)' tuple. |
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29 ''' |
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30 if mayhavepending(root): |
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31 try: |
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32 return (vfs('%s.pending' % filename, **kwargs), True) |
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33 except IOError as inst: |
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34 if inst.errno != errno.ENOENT: |
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35 raise |
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36 return (vfs(filename, **kwargs), False) |