contrib/debugcmdserver.py

hgweb: extract changelist entry generation into own function

I want to supplement changelist entries (used by shortlog and changelog
endpoints) with custom metadata from an extension. i.e. I have extra
per-changeset metadata that I wish to make available to templates so it
can be rendered on hgweb.

To facilitate this, I've extracted the logic for creating a changeset
data structure into its own function, where it can be wrapped by
extensions.

Ideally, hgweb would use the same templater as the command line and have
full access to templatekw.keywords. But that's a lot of work. This patch
gets us some of the benefit without all the work.

Many other hgweb commands could benefit from similar refactorings. I'm
going to wait to see how this patch is received before I go crazy on
extracting inline functions.

#!/usr/bin/env python
#
# Dumps output generated by Mercurial's command server in a formatted style to a
# given file or stderr if '-' is specified. Output is also written in its raw
# format to stdout.
#
# $ ./hg serve --cmds pipe | ./contrib/debugcmdserver.py -
# o, 52   -> 'capabilities: getencoding runcommand\nencoding: UTF-8'

import sys, struct

if len(sys.argv) != 2:
    print 'usage: debugcmdserver.py FILE'
    sys.exit(1)

outputfmt = '>cI'
outputfmtsize = struct.calcsize(outputfmt)

if sys.argv[1] == '-':
    log = sys.stderr
else:
    log = open(sys.argv[1], 'a')

def read(size):
    data = sys.stdin.read(size)
    if not data:
        raise EOFError
    sys.stdout.write(data)
    sys.stdout.flush()
    return data

try:
    while True:
        header = read(outputfmtsize)
        channel, length = struct.unpack(outputfmt, header)
        log.write('%s, %-4d' % (channel, length))
        if channel in 'IL':
            log.write(' -> waiting for input\n')
        else:
            data = read(length)
            log.write(' -> %r\n' % data)
        log.flush()
except EOFError:
    pass
finally:
    if log != sys.stderr:
        log.close()