[PATCH] tr-summary: keep a weakref to the unfiltered repository

Boris Feld boris.feld at octobus.net
Sat Nov 25 16:35:51 EST 2017

# HG changeset patch
# User Boris Feld <boris.feld at octobus.net>
# Date 1511578301 18000
#      Fri Nov 24 21:51:41 2017 -0500
# Branch stable
# Node ID a2eccde70ce65f9f0e8735e1bc8d51f58c8cdd71
# Parent  02845f7441aff30bc01975a5881cabfa922c12d4
# EXP-Topic callback-error
# Available At https://bitbucket.org/octobus/mercurial-devel/
#              hg pull https://bitbucket.org/octobus/mercurial-devel/ -r a2eccde70ce6
tr-summary: keep a weakref to the unfiltered repository

Repoview can have a different life cycle, causing issue in some corner
cases. The particular instance that revealed this comes from localpeer. The
localpeer hold a reference to the unfiltered repository, but calling 'local()'
will create an on-demand 'visible' repoview. That repoview can be garbaged
collected any time. Here is a simplified step by step reproduction::

    1) tr = peer.local().transaction('foo')
    2) tr.close()

After (1), the repoview object is garbage collected, so weakref used in (2)
point to nothing.

Thanks to Sean Farley for helping raising and debugging this issue.

diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -1233,9 +1233,17 @@ def registersummarycallback(repo, otr, t
     def reportsummary(func):
         """decorator for report callbacks."""
-        reporef = weakref.ref(repo)
+        # The repoview life cycle is shorter than the one of the actual
+        # underlying repository. So the filtered object can die before the
+        # weakref is used leading to troubles. We keep a reference to the
+        # unfiltered object and restore the filtering when retrieving the
+        # repository through the weakref.
+        filtername = repo.filtername
+        reporef = weakref.ref(repo.unfiltered())
         def wrapped(tr):
             repo = reporef()
+            if filtername:
+                repo = repo.filtered(filtername)
             func(repo, tr)
         newcat = '%2i-txnreport' % len(categories)
         otr.addpostclose(newcat, wrapped)

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