profile: upgrade the "profile" context manager to a full class So far we have been able to use a simple decorator for this. However using the current context manager makes the scope of the profiling in dispatch constrainted and the time frame to decide to enable profiling quite limited (using "maybeprofile") This is the first step toward the ability to enable the profiling from within the profiling scope. eg:: with maybeprofiling(ui) as profiler: ... bar.foo(): ... if options['profile']: profiler.start() ... fooz() ... My target usecase is adding support for "--profile" to alias definitions with effect. These are to be used with "profiling.output=blackbox" to gather data about operation that get slow from time to time (eg: pull being minutes instead of seconds from time to time). Of course, in such case, the scope of the profiling would be smaller since profiler would be started after running extensions 'reposetup' (and other potentially costly logic), but these are not relevant for my target usecase (multiple second commits, multiple tens of seconds pull). Currently adding '--profile' to a command through alias requires to re-spin a Mercurial binary (using "!$HG" in alias), which as a significant performance impact, especially in context where startup performance is being worked on... An alternative approach would be to stop using the context manager in dispatch and move back to a try/finally setup.

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#!/usr/bin/env python

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#

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# Dumps output generated by Mercurial's command server in a formatted style to a

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# given file or stderr if '-' is specified. Output is also written in its raw

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# format to stdout.

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#

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# $ ./hg serve --cmds pipe | ./contrib/debugcmdserver.py -

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# o, 52   -> 'capabilities: getencoding runcommand\nencoding: UTF-8'

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from __future__ import absolute_import, print_function

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import struct

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import sys

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if len(sys.argv) != 2:

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    print('usage: debugcmdserver.py FILE')

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    sys.exit(1)

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outputfmt = '>cI'

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outputfmtsize = struct.calcsize(outputfmt)

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if sys.argv[1] == '-':

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    log = sys.stderr

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else:

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    log = open(sys.argv[1], 'a')

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def read(size):

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    data = sys.stdin.read(size)

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    if not data:

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        raise EOFError

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    sys.stdout.write(data)

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    sys.stdout.flush()

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    return data

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try:

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    while True:

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        header = read(outputfmtsize)

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        channel, length = struct.unpack(outputfmt, header)

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        log.write('%s, %-4d' % (channel, length))

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        if channel in 'IL':

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            log.write(' -> waiting for input\n')

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        else:

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            data = read(length)

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            log.write(' -> %r\n' % data)

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        log.flush()

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except EOFError:

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    pass

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finally:

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    if log != sys.stderr:

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        log.close()