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.
#require cvs
$ filterpath()
> {
> eval "$@" | sed "s:$CVSROOT:*REPO*:g"
> }
$ cvscall()
> {
> cvs -f "$@"
> }
output of 'cvs ci' varies unpredictably, so discard most of it
-- just keep the part that matters
$ cvsci()
> {
> cvs -f ci -f "$@" > /dev/null
> }
$ hgcat()
> {
> hg --cwd src-hg cat -r tip "$1"
> }
$ echo "[extensions]" >> $HGRCPATH
$ echo "convert = " >> $HGRCPATH
create cvs repository
$ mkdir cvsmaster
$ cd cvsmaster
$ CVSROOT=`pwd`
$ export CVSROOT
$ CVS_OPTIONS=-f
$ export CVS_OPTIONS
$ cd ..
$ rmdir cvsmaster
$ filterpath cvscall -Q -d "$CVSROOT" init
checkout #1: add foo.txt
$ cvscall -Q checkout -d cvsworktmp .
$ cd cvsworktmp
$ mkdir foo
$ cvscall -Q add foo
$ cd foo
$ echo foo > foo.txt
$ cvscall -Q add foo.txt
$ cvsci -m "add foo.txt" foo.txt
$ cd ../..
$ rm -rf cvsworktmp
checkout #2: create MYBRANCH1 and modify foo.txt on it
$ cvscall -Q checkout -d cvswork foo
$ cd cvswork
$ cvscall -q rtag -b -R MYBRANCH1 foo
$ cvscall -Q update -P -r MYBRANCH1
$ echo bar > foo.txt
$ cvsci -m "bar" foo.txt
$ echo baz > foo.txt
$ cvsci -m "baz" foo.txt
create MYBRANCH1_2 and modify foo.txt some more
$ cvscall -q rtag -b -R -r MYBRANCH1 MYBRANCH1_2 foo
$ cvscall -Q update -P -r MYBRANCH1_2
$ echo bazzie > foo.txt
$ cvsci -m "bazzie" foo.txt
create MYBRANCH1_1 and modify foo.txt yet again
$ cvscall -q rtag -b -R MYBRANCH1_1 foo
$ cvscall -Q update -P -r MYBRANCH1_1
$ echo quux > foo.txt
$ cvsci -m "quux" foo.txt
merge MYBRANCH1 to MYBRANCH1_1
$ filterpath cvscall -Q update -P -jMYBRANCH1
rcsmerge: warning: conflicts during merge
RCS file: *REPO*/foo/foo.txt,v
retrieving revision 1.1
retrieving revision 1.1.2.2
Merging differences between 1.1 and 1.1.2.2 into foo.txt
carefully placed sleep to dodge cvs bug (optimization?) where it
sometimes ignores a "commit" command if it comes too fast (the -f
option in cvsci seems to work for all the other commits in this
script)
$ sleep 1
$ echo xyzzy > foo.txt
$ cvsci -m "merge1+clobber" foo.txt
#if unix-permissions
return to trunk and merge MYBRANCH1_2
$ cvscall -Q update -P -A
$ filterpath cvscall -Q update -P -jMYBRANCH1_2
RCS file: *REPO*/foo/foo.txt,v
retrieving revision 1.1
retrieving revision 1.1.2.2.2.1
Merging differences between 1.1 and 1.1.2.2.2.1 into foo.txt
$ cvsci -m "merge2" foo.txt
$ REALCVS=`which cvs`
$ echo "for x in \$*; do if [ \"\$x\" = \"rlog\" ]; then echo \"RCS file: $CVSROOT/foo/foo.txt,v\"; cat \"$TESTDIR/test-convert-cvsnt-mergepoints.rlog\"; exit 0; fi; done; $REALCVS \$*" > ../cvs
$ chmod +x ../cvs
$ PATH=..:${PATH} hg debugcvsps --parents foo
collecting CVS rlog
7 log entries
creating changesets
7 changeset entries
---------------------
PatchSet 1
Date: * (glob)
Author: user
Branch: HEAD
Tag: (none)
Branchpoints: MYBRANCH1, MYBRANCH1_1
Log:
foo.txt
Members:
foo.txt:INITIAL->1.1
---------------------
PatchSet 2
Date: * (glob)
Author: user
Branch: MYBRANCH1
Tag: (none)
Parent: 1
Log:
bar
Members:
foo.txt:1.1->1.1.2.1
---------------------
PatchSet 3
Date: * (glob)
Author: user
Branch: MYBRANCH1
Tag: (none)
Branchpoints: MYBRANCH1_2
Parent: 2
Log:
baz
Members:
foo.txt:1.1.2.1->1.1.2.2
---------------------
PatchSet 4
Date: * (glob)
Author: user
Branch: MYBRANCH1_1
Tag: (none)
Parent: 1
Log:
quux
Members:
foo.txt:1.1->1.1.4.1
---------------------
PatchSet 5
Date: * (glob)
Author: user
Branch: MYBRANCH1_2
Tag: (none)
Parent: 3
Log:
bazzie
Members:
foo.txt:1.1.2.2->1.1.2.2.2.1
---------------------
PatchSet 6
Date: * (glob)
Author: user
Branch: HEAD
Tag: (none)
Parents: 1,5
Log:
merge
Members:
foo.txt:1.1->1.2
---------------------
PatchSet 7
Date: * (glob)
Author: user
Branch: MYBRANCH1_1
Tag: (none)
Parents: 4,3
Log:
merge
Members:
foo.txt:1.1.4.1->1.1.4.2
#endif
$ cd ..