Abort: cannot follow file not in parent revision: "tracext/hg/backend.py"

[Christian Boos]

Looks like we have a problem with walkchangerevs once again…

It doesn't happen for me with with Mercurial 2.0.2, but happens here with 2.2.1.

How to Reproduce

While doing a GET operation on /log/mercurial-plugin/tracext/hg/backend.py, Trac issued an internal error.

Request parameters:

{'path': u'/mercurial-plugin/tracext/hg/backend.py', 'rev': u'3'}

User agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/536.11 (KHTML, like Gecko) Chrome/20.0.1132.21 Safari/536.11

System Information

Trac	0.13dev-r11050

…

Mercurial	2.2.1
mod_wsgi	3.3 (WSGIProcessGroup trac WSGIApplicationGroup %{GLOBAL})
Python	2.6.6 (r266:84292, Dec 26 2010, 22:48:11) [GCC 4.4.5]

Enabled Plugins

TracMercurial

0.13.0.5dev

…

Python Traceback

Traceback (most recent call last):
  File "/usr/local/virtualenv/0.13-stable/lib/python2.6/site-packages/Trac-0.13dev_r11050-py2.6.egg/trac/web/main.py", line 480, in _dispatch_request
    dispatcher.dispatch(req)
  File "/usr/local/virtualenv/0.13-stable/lib/python2.6/site-packages/Trac-0.13dev_r11050-py2.6.egg/trac/web/main.py", line 198, in dispatch
    resp = chosen_handler.process_request(req)
  File "/usr/local/virtualenv/0.13-stable/lib/python2.6/site-packages/Trac-0.13dev_r11050-py2.6.egg/trac/versioncontrol/web_ui/log.py", line 172, in process_request
    for old_path, old_rev, old_chg in history():
  File "/usr/local/virtualenv/0.13-stable/lib/python2.6/site-packages/Trac-0.13dev_r11050-py2.6.egg/trac/versioncontrol/web_ui/log.py", line 163, in history
    for h in node.get_history():
  File "/usr/local/virtualenv/0.13-stable/lib/python2.6/site-packages/TracMercurial-0.13.0.5dev-py2.6.egg/tracext/hg/backend.py", line 1092, in _get_history_1_4
    for ctx in cmdutil.walkchangerevs(repo, matcher, opts, prep):
  File "/usr/lib/python2.6/dist-packages/mercurial/cmdutil.py", line 1058, in walkchangerevs
    for file_, node in iterfiles():
  File "/usr/lib/python2.6/dist-packages/mercurial/cmdutil.py", line 1052, in iterfiles
    'revision: "%s"') % filename)
Abort: cannot follow file not in parent revision: "tracext/hg/backend.py"

[Christian Boos]

The check which fails was apparently added here:

​http://selenic.com/pipermail/mercurial-devel/2012-February/038249.html

[Christian Boos]

i.e. ​hg:60101427d618

[Christian Boos]

+            pctx = repo['.']

Ugh. Time to say goodbye to walkchangerevs…

[Christian Boos]

The call in question in the plugin is: source:mercurial-plugin/tracext/hg/backend.py@8af21bda2b3e#L1064​ (in _get_history_1_4)

[Christian Boos]

While waiting for a fix in Mercurial itself, one can apply the following patch to mercurial:

mercurial/cmdutil.py

@@ -996 +996 @@
     revs = scmutil.revrange(repo, opts['rev'] or [defrange])
     if not revs:
         return []
+    pctx = repo[revs[0]]
     wanted = set()
     slowpath = match.anypats() or (match.files() and opts.get('removed'))
     fncache = {}
@@ -1044 +1045 @@
 
             return reversed(revs)
         def iterfiles():
-            pctx = repo['.']
             for filename in match.files():
                 if follow:
                     if filename not in pctx:

[Christian Boos]

As the ​discussion for fixing that issue in Mercurial went nowhere (also because walkchangerevs is seen as deprecated anyway), let's try to find a workaround.

[Christian Boos]

Looks like I forgot to push a crude workaround I had for this issue… [a0a40cb30265/mercurial-plugin].

Doing the follow part correctly is still TODO.