view tests/test-propertycache.py.out @ 42377:0546ead39a7e stable

manifest: avoid corruption by dropping removed files with pure (issue5801)

Previously, removed files would simply be marked by overwriting the first byte
with NUL and dropping their entry in `self.position`.  But no effort was made to
ignore them when compacting the dictionary into text form.  This allowed them to
slip into the manifest revision, since the code seems to be trying to minimize
the string operations by copying as large a chunk as possible.  As part of this,
compact() walks the existing text based on entries in the `positions` list, and
consumed everything up to the next position entry.   This typically resulted in
a ValueError complaining about unsorted manifest entries.

Sometimes it seems that files do get dropped in large repos- it seems to
correspond to there being a new entry that would take the same slot.  A much
more trivial problem is that if the only changes were removals, `_compact()`
didn't even run because `__delitem__` doesn't add anything to `self.extradata`.
Now there's an explicit variable to flag this, both to allow `_compact()` to
run, and to avoid searching the manifest in cases where there are no removals.

In practice, this behavior was mostly obscured by the check in fastdelta() which
takes a different path that explicitly drops removed files if there are fewer
than 1000 changes.  However, timeless has a repo where after rebasing tens of
commits, a totally different path[1] is taken that bypasses the change count
check and hits this problem.

[1] https://www.mercurial-scm.org/repo/hg/file/2338bdea4474/mercurial/manifest.py#l1511

=== property cache ===

calllog: []
cached value (unfiltered): NOCACHE

= first access on unfiltered, should do a call
access: 0
calllog: [0]
cached value (unfiltered): 0

= second access on unfiltered, should not do call
access 0
calllog: [0]
cached value (unfiltered): 0

= first access on "visible" view, should do a call
cached value ("visible" view): NOCACHE
access: 7
calllog: [0, 7]
cached value (unfiltered): 0
cached value ("visible" view): 7

= second access on "visible view", should not do call
access: 7
calllog: [0, 7]
cached value (unfiltered): 0
cached value ("visible" view): 7

= no effect on other view
cached value ("immutable" view): NOCACHE
access: 9
calllog: [0, 7, 9]
cached value (unfiltered): 0
cached value ("visible" view): 7
cached value ("immutable" view): 9


=== unfiltered property cache ===

unficalllog: []
cached value (unfiltered):       NOCACHE
cached value ("visible" view):   NOCACHE
cached value ("immutable" view): NOCACHE

= first access on unfiltered, should do a call
access (unfiltered): 100
unficalllog: [100]
cached value (unfiltered):       100

= second access on unfiltered, should not do call
access (unfiltered): 100
unficalllog: [100]
cached value (unfiltered):       100

= access on view should use the unfiltered cache
access (unfiltered):       100
access ("visible" view):   100
access ("immutable" view): 100
unficalllog: [100]
cached value (unfiltered):       100
cached value ("visible" view):   NOCACHE
cached value ("immutable" view): NOCACHE

= even if we clear the unfiltered cache
cached value (unfiltered):       NOCACHE
cached value ("visible" view):   NOCACHE
cached value ("immutable" view): NOCACHE
unficalllog: [100]
access ("visible" view):   100
unficalllog: [100, 100]
cached value (unfiltered):       100
cached value ("visible" view):   NOCACHE
cached value ("immutable" view): NOCACHE
access ("immutable" view): 100
unficalllog: [100, 100]
cached value (unfiltered):       100
cached value ("visible" view):   NOCACHE
cached value ("immutable" view): NOCACHE
access (unfiltered):       100
unficalllog: [100, 100]
cached value (unfiltered):       100
cached value ("visible" view):   NOCACHE
cached value ("immutable" view): NOCACHE