extensions: refuse to load extensions if minimum hg version not met
As the author of several 3rd party extensions, I frequently see bug
reports from users attempting to run my extension with an old version
of Mercurial that I no longer support in my extension. Oftentimes, the
extension will import just fine. But as soon as we run extsetup(),
reposetup(), or get into the guts of a wrapped function, we encounter
an exception and abort. Today, Mercurial will print a message about
extensions that don't have a "testedwith" declaring explicit
compatibility with the current version.
The existing mechanism is a good start. But it isn't as robust as I
would like. Specifically, Mercurial assumes compatibility by default.
This means extension authors must perform compatibility checking in
their extsetup() or we wait and see if we encounter an abort at
runtime. And, compatibility checking can involve a lot of code and
lots of error checking. It's a lot of effort for extension authors.
Oftentimes, extension authors know which versions of Mercurial there
extension works on and more importantly where it is broken.
This patch introduces a magic "minimumhgversion" attribute in
extensions. When found, the extension loading mechanism will compare
the declared version against the current Mercurial version. If the
extension explicitly states we require a newer Mercurial version, a
warning is printed and the extension isn't loaded beyond importing
the Python module. This causes a graceful failure while alerting
the user of the compatibility issue.
I would be receptive to the idea of making the failure more fatal.
However, care would need to be taken to not criple every hg command.
e.g. the user may use `hg config` to fix the hgrc and if we aborted
trying to run that, the user would effectively be locked out of `hg`!
A potential future improvement to this functionality would be to catch
ImportError for the extension/module and parse the source code for
"minimumhgversion = 'XXX'" and do similar checking. This way we could
give more information about why the extension failed to load.
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init foo
$ cd foo
$ echo a > a
$ hg ci -qAm a
Default queue:
$ hg qqueue
patches (active)
$ echo b > a
$ hg qnew -fgDU somestuff
Applied patches in default queue:
$ hg qap
somestuff
Try to change patch (create succeeds, switch fails):
$ hg qqueue foo --create
abort: new queue created, but cannot make active as patches are applied
[255]
$ hg qqueue
foo
patches (active)
Empty default queue:
$ hg qpop
popping somestuff
patch queue now empty
Switch queue:
$ hg qqueue foo
$ hg qqueue
foo (active)
patches
List queues, quiet:
$ hg qqueue --quiet
foo
patches
Fail creating queue with already existing name:
$ hg qqueue --create foo
abort: queue "foo" already exists
[255]
$ hg qqueue
foo (active)
patches
Create new queue for rename:
$ hg qqueue --create bar
$ hg qqueue
bar (active)
foo
patches
Rename queue, same name:
$ hg qqueue --rename bar
abort: can't rename "bar" to its current name
[255]
Rename queue to existing:
$ hg qqueue --rename foo
abort: queue "foo" already exists
[255]
Rename queue:
$ hg qqueue --rename buz
$ hg qqueue
buz (active)
foo
patches
Switch back to previous queue:
$ hg qqueue foo
$ hg qqueue --delete buz
$ hg qqueue
foo (active)
patches
Create queue for purge:
$ hg qqueue --create purge-me
$ hg qqueue
foo
patches
purge-me (active)
Create patch for purge:
$ hg qnew patch-purge-me
$ ls -1d .hg/patches-purge-me 2>/dev/null || true
.hg/patches-purge-me
$ hg qpop -a
popping patch-purge-me
patch queue now empty
Purge queue:
$ hg qqueue foo
$ hg qqueue --purge purge-me
$ hg qqueue
foo (active)
patches
$ ls -1d .hg/patches-purge-me 2>/dev/null || true
Unapplied patches:
$ hg qun
$ echo c > a
$ hg qnew -fgDU otherstuff
Fail switching back:
$ hg qqueue patches
abort: new queue created, but cannot make active as patches are applied
[255]
Fail deleting current:
$ hg qqueue foo --delete
abort: cannot delete currently active queue
[255]
Switch back and delete foo:
$ hg qpop -a
popping otherstuff
patch queue now empty
$ hg qqueue patches
$ hg qqueue foo --delete
$ hg qqueue
patches (active)
Tricky cases:
$ hg qqueue store --create
$ hg qnew journal
$ hg qqueue
patches
store (active)
$ hg qpop -a
popping journal
patch queue now empty
$ hg qqueue patches
$ hg qun
somestuff
Invalid names:
$ hg qqueue test/../../bar --create
abort: invalid queue name, may not contain the characters ":\/."
[255]
$ hg qqueue . --create
abort: invalid queue name, may not contain the characters ":\/."
[255]
$ cd ..