perf: add historical support of ui.load()

ui.load() has been available since d83ca854 and at the time of writing isn't
available on stable branch breaking benchmarking newer stable revisions.

Add historical portability policy note on contrib/benchmarks

contrib/benchmarks/__init__.py

@@ -1,102 +1,113 b''
 # __init__.py - asv benchmark suite
 #
 # Copyright 2016 Logilab SA <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
+# "historical portability" policy of contrib/benchmarks:
+#
+# We have to make this code work correctly with current mercurial stable branch
+# and if possible with reasonable cost with early Mercurial versions.
+
 '''ASV (https://asv.readthedocs.io) benchmark suite
 
 Benchmark are parameterized against reference repositories found in the
 directory pointed by the REPOS_DIR environment variable.
 
 Invocation example:
 
     $ export REPOS_DIR=~/hgperf/repos
     # run suite on given revision
     $ asv --config contrib/asv.conf.json run REV
     # run suite on new changesets found in stable and default branch
     $ asv --config contrib/asv.conf.json run NEW
     # display a comparative result table of benchmark results between two given
     # revisions
     $ asv --config contrib/asv.conf.json compare REV1 REV2
     # compute regression detection and generate ASV static website
     $ asv --config contrib/asv.conf.json publish
     # serve the static website
     $ asv --config contrib/asv.conf.json preview
 '''
 
 from __future__ import absolute_import
 
 import functools
 import os
 import re
 
 from mercurial import (
     extensions,
     hg,
     ui as uimod,
+    util,
 )
 
 basedir = os.path.abspath(os.path.join(os.path.dirname(__file__),
                           os.path.pardir, os.path.pardir))
 reposdir = os.environ['REPOS_DIR']
 reposnames = [name for name in os.listdir(reposdir)
               if os.path.isdir(os.path.join(reposdir, name, ".hg"))]
 if not reposnames:
     raise ValueError("No repositories found in $REPO_DIR")
 outputre = re.compile((r'! wall (\d+.\d+) comb \d+.\d+ user \d+.\d+ sys '
                        r'\d+.\d+ \(best of \d+\)'))
 
 def runperfcommand(reponame, command, *args, **kwargs):
     os.environ["HGRCPATH"] = os.environ.get("ASVHGRCPATH", "")
-    ui = uimod.ui.load()
+    # for "historical portability"
+    # ui.load() has been available since d83ca85
+    if util.safehasattr(uimod.ui, "load"):
+        ui = uimod.ui.load()
+    else:
+        ui = uimod.ui()
     repo = hg.repository(ui, os.path.join(reposdir, reponame))
     perfext = extensions.load(ui, 'perfext',
                               os.path.join(basedir, 'contrib', 'perf.py'))
     cmd = getattr(perfext, command)
     ui.pushbuffer()
     cmd(ui, repo, *args, **kwargs)
     output = ui.popbuffer()
     match = outputre.search(output)
     if not match:
         raise ValueError("Invalid output {0}".format(output))
     return float(match.group(1))
 
 def perfbench(repos=reposnames, name=None, params=None):
     """decorator to declare ASV benchmark based on contrib/perf.py extension
 
     An ASV benchmark is a python function with the given attributes:
 
     __name__: should start with track_, time_ or mem_ to be collected by ASV
     params and param_name: parameter matrix to display multiple graphs on the
     same page.
     pretty_name: If defined it's displayed in web-ui instead of __name__
     (useful for revsets)
     the module name is prepended to the benchmark name and displayed as
     "category" in webui.
 
     Benchmarks are automatically parameterized with repositories found in the
     REPOS_DIR environment variable.
 
     `params` is the param matrix in the form of a list of tuple
     (param_name, [value0, value1])
 
     For example [(x, [a, b]), (y, [c, d])] declare benchmarks for
     (a, c), (a, d), (b, c) and (b, d).
     """
     params = list(params or [])
     params.insert(0, ("repo", repos))
 
     def decorator(func):
         @functools.wraps(func)
         def wrapped(repo, *args):
             def perf(command, *a, **kw):
                 return runperfcommand(repo, command, *a, **kw)
             return func(perf, *args)
 
         wrapped.params = [p[1] for p in params]
         wrapped.param_names = [p[0] for p in params]
         wrapped.pretty_name = name
         return wrapped
     return decorator