[PATCH 2 of 2] repovfs: add a ward to check if locks are properly taken

[Pierre-Yves David]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at ens-lyon.org>
# Date 1470606246 -7200
#      Sun Aug 07 23:44:06 2016 +0200
# Node ID dd18fd65bc8322a8bbacf2b165228b843ba849ae
# Parent  b84b218971cfb131023b7e9550cb112e6195841b
# EXP-Topic vfs.ward
repovfs: add a ward to check if locks are properly taken

We use the 'ward' feature introduced in the previous email to check for locks
when accessing file in '.hg' for writting. Another changeset will add a 'ward'
for the store vfs (svfs).

This 'ward' system have caught an handful of locking issue that  has been fixed
in previous series. I expect another batch to be caught in third party
extensions.

We introduce two exceptions from extensions 'blackbox.log' (because a lot of
read-only operations add entry to it), and 'last-email.txt' (because 'hg email'
is currently a read only operation and there is value to keep it this way).

diff -r b84b218971cf -r dd18fd65bc83 hgext/blackbox.py
--- a/hgext/blackbox.py	Thu Aug 04 17:07:46 2016 +0200
+++ b/hgext/blackbox.py	Sun Aug 07 23:44:06 2016 +0200
@@ -220,6 +220,7 @@ def reposetup(ui, repo):
 
     if util.safehasattr(ui, 'setrepo'):
         ui.setrepo(repo)
+    repo._wlockfreeprefix.add('blackbox.log')
 
 @command('^blackbox',
     [('l', 'limit', 10, _('the number of events to show')),
diff -r b84b218971cf -r dd18fd65bc83 hgext/patchbomb.py
--- a/hgext/patchbomb.py	Thu Aug 04 17:07:46 2016 +0200
+++ b/hgext/patchbomb.py	Sun Aug 07 23:44:06 2016 +0200
@@ -110,6 +110,10 @@ def uisetup(ui):
     cmdutil.extraexport.append('pullurl')
     cmdutil.extraexportmap['pullurl'] = _addpullheader
 
+def reposetup(ui, repo):
+    if not repo.local():
+        return
+    repo._wlockfreeprefix.add('last-email.txt')
 
 def prompt(ui, prompt, default=None, rest=':'):
     if default:
diff -r b84b218971cf -r dd18fd65bc83 mercurial/localrepo.py
--- a/mercurial/localrepo.py	Thu Aug 04 17:07:46 2016 +0200
+++ b/mercurial/localrepo.py	Sun Aug 07 23:44:06 2016 +0200
@@ -244,6 +244,16 @@ class localrepository(object):
     # only functions defined in module of enabled extensions are invoked
     featuresetupfuncs = set()
 
+    # list of prefix for file which can be written without 'wlock'
+    # Extensions should extend this list when needed
+    _wlockfreeprefix = set([# We migh consider requiring 'wlock' for the next
+                            # two, but pretty much all the existing code assume
+                            # wlock is not needed so we keep them excluded for
+                            # now.
+                            'hgrc',
+                            'requires',
+                            ])
+
     def __init__(self, baseui, path=None, create=False):
         self.requirements = set()
         self.wvfs = scmutil.vfs(path, expandpath=True, realpath=True)
@@ -254,11 +264,15 @@ class localrepository(object):
         self.auditor = pathutil.pathauditor(self.root, self._checknested)
         self.nofsauditor = pathutil.pathauditor(self.root, self._checknested,
                                                 realfs=False)
-        self.vfs = scmutil.vfs(self.path)
-        self.opener = self.vfs
         self.baseui = baseui
         self.ui = baseui.copy()
         self.ui.copy = baseui.copy # prevent copying repo configuration
+        _vfsward = None
+        if (self.ui.configbool('devel', 'all-warnings') or
+            self.ui.configbool('devel', 'check-locks')):
+                _vfsward = self._getvfsward()
+        self.vfs = scmutil.vfs(self.path, ward=_vfsward)
+        self.opener = self.vfs
         # A list of callback to shape the phase if no data were found.
         # Callback are in the form: func(repo, roots) --> processed root.
         # This list it to be filled by extension during repo setup
@@ -357,6 +371,36 @@ class localrepository(object):
         # generic mapping between names and nodes
         self.names = namespaces.namespaces()
 
+    def _getvfsward(self):
+        """build a ward for self.vfs"""
+        rref = weakref.ref(self)
+        def checkvfs(f, mode):
+            repo = rref()
+            if (repo is None
+                or not util.safehasattr(repo, '_wlockref')
+                or not util.safehasattr(repo, '_lockref')):
+                return
+            if mode in ('r', 'rb'):
+                return
+            assert f.startswith(repo.path)
+            # truncate name relative to the repository (.hg)
+            relname = f[len(repo.path) + 1:]
+            if relname.startswith('journal.'):
+                # journal is covered by 'lock'
+                if repo._currentlock(repo._lockref) is None:
+                    repo.ui.develwarn('write with no lock: "%s"' % relname,
+                                      stacklevel=2)
+            elif repo._currentlock(repo._wlockref) is None:
+                # rest of vfs file are covered by 'wlock'
+                #
+                # exclude special files
+                for prefix in self._wlockfreeprefix:
+                    if relname.startswith(prefix):
+                        return
+                repo.ui.develwarn('write with no wlock: "%s"' % relname,
+                                  stacklevel=2)
+        return checkvfs
+
     def close(self):
         self._writecaches()
 
diff -r b84b218971cf -r dd18fd65bc83 tests/test-devel-warnings.t
--- a/tests/test-devel-warnings.t	Thu Aug 04 17:07:46 2016 +0200
+++ b/tests/test-devel-warnings.t	Sun Aug 07 23:44:06 2016 +0200
@@ -105,6 +105,7 @@
   $ hg add a
   $ hg commit -m a
   $ hg stripintr
+  devel-warn: write with no wlock: "strip-backup/*-backup.hg" at: */mercurial/changegroup.py:* (writechunks) (glob)
   saved backup bundle to $TESTTMP/lock-checker/.hg/strip-backup/*-backup.hg (glob)
   abort: programming error: cannot strip from inside a transaction
   (contact your extension maintainer)