Mercurial > hg
view tests/test-minirst.py @ 44950:f9734b2d59cc
py3: make stdout line-buffered if connected to a TTY
Status messages that are to be shown on the terminal should be written to the
file descriptor before anything further is done, to keep the user updated.
One common way to achieve this is to make stdout line-buffered if it is
connected to a TTY. This is done on Python 2 (except on Windows, where libc,
which the CPython 2 streams depend on, does not properly support this).
Python 3 rolls it own I/O streams. On Python 3, buffered binary streams can't be
set line-buffered. The previous code (added in 227ba1afcb65) incorrectly
assumed that on Python 3, pycompat.stdout (sys.stdout.buffer) is already
line-buffered. However the interpreter initializes it with a block-buffered
stream or an unbuffered stream (when the -u option or the PYTHONUNBUFFERED
environment variable is set), never with a line-buffered stream.
One example where the current behavior is unacceptable is when running
`hg pull https://www.mercurial-scm.org/repo/hg` on Python 3, where the line
"pulling from https://www.mercurial-scm.org/repo/hg" does not appear on the
terminal before the hg process blocks while waiting for the server.
Various approaches to fix this problem are possible, including:
1. Weaken the contract of procutil.stdout to not give any guarantees about
buffering behavior. In this case, users of procutil.stdout need to be
changed to do enough flushes. In particular,
1. either ui must insert enough flushes for ui.write() and friends, or
2. ui.write() and friends get split into flushing and fully buffered
methods, or
3. users of ui.write() and friends must flush explicitly.
2. Make stdout unbuffered.
3. Make stdout line-buffered. Since Python 3 does not natively support that for
binary streams, we must implement it ourselves.
(2.) is problematic because using unbuffered I/O changes the performance
characteristics significantly compared to line-buffered (which is used on
Python 2) and this would be a regression.
(1.2.) and (1.3) are a substantial amount of work. It’s unclear whether the
added complexity would be justified, given that raw performance doesn’t matter
that much when writing to a terminal much faster than the user could read it.
(1.1.) pushes complexity into the ui class instead of separating the concern of
how stdout is buffered. Other users of procutil.stdout would still need to take
care of the flushes.
This patch implements (3.). The general performance considerations are very
similar to (1.1.). The extra method invocation and method forwarding add a
little more overhead if the class is used. In exchange, it doesn’t add overhead
if not used.
For the benchmarks, I compared the previous implementation (incorrect on Python
3), (1.1.), (3.) and (2.). The command was chosen so that the streams were
configured as if they were writing to a TTY, but actually write to a pager,
which is also the default:
HGRCPATH=/dev/null python3 ./hg --cwd ~/vcs/mozilla-central --time --pager yes --config pager.pager='cat > /dev/null' status --all
previous:
time: real 7.880 secs (user 7.290+0.050 sys 0.580+0.170)
time: real 7.830 secs (user 7.220+0.070 sys 0.590+0.140)
time: real 7.800 secs (user 7.210+0.050 sys 0.570+0.170)
(1.1.) using Yuya Nishihara’s patch:
time: real 9.860 secs (user 8.670+0.350 sys 1.160+0.830)
time: real 9.540 secs (user 8.430+0.370 sys 1.100+0.770)
time: real 9.830 secs (user 8.630+0.370 sys 1.180+0.840)
(3.) using this patch:
time: real 9.580 secs (user 8.480+0.350 sys 1.090+0.770)
time: real 9.670 secs (user 8.480+0.330 sys 1.170+0.860)
time: real 9.640 secs (user 8.500+0.350 sys 1.130+0.810)
(2.) using a previous patch by me:
time: real 10.480 secs (user 8.850+0.720 sys 1.590+1.500)
time: real 10.490 secs (user 8.750+0.750 sys 1.710+1.470)
time: real 10.240 secs (user 8.600+0.700 sys 1.590+1.510)
As expected, there’s no difference on Python 2, as exactly the same code paths
are used:
previous:
time: real 6.950 secs (user 5.870+0.330 sys 1.070+0.770)
time: real 7.040 secs (user 6.040+0.360 sys 0.980+0.750)
time: real 7.070 secs (user 5.950+0.360 sys 1.100+0.760)
this patch:
time: real 7.010 secs (user 5.900+0.390 sys 1.070+0.730)
time: real 7.000 secs (user 5.850+0.350 sys 1.120+0.760)
time: real 7.000 secs (user 5.790+0.380 sys 1.170+0.710)
author | Manuel Jacob <me@manueljacob.de> |
---|---|
date | Wed, 10 Jun 2020 13:02:39 +0200 |
parents | 2372284d9457 |
children | aaff3bc75306 |
line wrap: on
line source
from __future__ import absolute_import, print_function from mercurial import minirst from mercurial.utils import stringutil def debugformat(text, form, **kwargs): blocks, pruned = minirst.parse(text, **kwargs) if form == b'html': print("html format:") out = minirst.format(text, style=form, **kwargs) else: print("%d column format:" % form) out = minirst.format(text, width=form, **kwargs) print("-" * 70) print(out[:-1].decode('utf8')) if kwargs.get('keep'): print("-" * 70) print(stringutil.pprint(pruned).decode('utf8')) print("-" * 70) print() def debugformats(title, text, **kwargs): print("== %s ==" % title) debugformat(text, 60, **kwargs) debugformat(text, 30, **kwargs) debugformat(text, b'html', **kwargs) paragraphs = b""" This is some text in the first paragraph. A small indented paragraph. It is followed by some lines containing random whitespace. \n \n \nThe third and final paragraph. """ debugformats('paragraphs', paragraphs) definitions = b""" A Term Definition. The indented lines make up the definition. Another Term Another definition. The final line in the definition determines the indentation, so this will be indented with four spaces. A Nested/Indented Term Definition. """ debugformats('definitions', definitions) literals = br""" The fully minimized form is the most convenient form:: Hello literal world In the partially minimized form a paragraph simply ends with space-double-colon. :: //////////////////////////////////////// long un-wrapped line in a literal block \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ :: This literal block is started with '::', the so-called expanded form. The paragraph with '::' disappears in the final output. """ debugformats('literals', literals) lists = b""" - This is the first list item. Second paragraph in the first list item. - List items need not be separated by a blank line. - And will be rendered without one in any case. We can have indented lists: - This is an indented list item - Another indented list item:: - A literal block in the middle of an indented list. (The above is not a list item since we are in the literal block.) :: Literal block with no indentation (apart from the two spaces added to all literal blocks). 1. This is an enumerated list (first item). 2. Continuing with the second item. (1) foo (2) bar 1) Another 2) List Line blocks are also a form of list: | This is the first line. The line continues here. | This is the second line. Bullet lists are also detected: * This is the first bullet * This is the second bullet It has 2 lines * This is the third bullet """ debugformats('lists', lists) options = b""" There is support for simple option lists, but only with long options: -X, --exclude filter an option with a short and long option with an argument -I, --include an option with both a short option and a long option --all Output all. --both Output both (this description is quite long). --long Output all day long. --par This option has two paragraphs in its description. This is the first. This is the second. Blank lines may be omitted between options (as above) or left in (as here). The next paragraph looks like an option list, but lacks the two-space marker after the option. It is treated as a normal paragraph: --foo bar baz """ debugformats('options', options) fields = b""" :a: First item. :ab: Second item. Indentation and wrapping is handled automatically. Next list: :small: The larger key below triggers full indentation here. :much too large: This key is big enough to get its own line. """ debugformats('fields', fields) containers = b""" Normal output. .. container:: debug Initial debug output. .. container:: verbose Verbose output. .. container:: debug Debug output. """ debugformats('containers (normal)', containers) debugformats('containers (verbose)', containers, keep=[b'verbose']) debugformats('containers (debug)', containers, keep=[b'debug']) debugformats( 'containers (verbose debug)', containers, keep=[b'verbose', b'debug'] ) roles = b"""Please see :hg:`add`.""" debugformats('roles', roles) sections = b""" Title ===== Section ------- Subsection '''''''''' Markup: ``foo`` and :hg:`help` ------------------------------ """ debugformats('sections', sections) admonitions = b""" .. note:: This is a note - Bullet 1 - Bullet 2 .. warning:: This is a warning Second input line of warning .. danger:: This is danger """ debugformats('admonitions', admonitions) comments = b""" Some text. .. A comment .. An indented comment Some indented text. .. Empty comment above """ debugformats('comments', comments) data = [ [b'a', b'b', b'c'], [b'1', b'2', b'3'], [b'foo', b'bar', b'baz this list is very very very long man'], ] rst = minirst.maketable(data, 2, True) table = b''.join(rst) print(table.decode('utf8')) debugformats('table', table) data = [ [b's', b'long', b'line\ngoes on here'], [b'', b'xy', b'tried to fix here\n by indenting'], ] rst = minirst.maketable(data, 1, False) table = b''.join(rst) print(table.decode('utf8')) debugformats('table+nl', table)