view tests/test-branch-option.t @ 20742:3681de20b0a7

parsers: fail fast if Python has wrong minor version (issue4110)

This change causes an informative ImportError to be raised when importing
the parsers extension module if the minor version of the currently-running
Python interpreter doesn't match that of the Python used when compiling
the extension module.

This change also exposes a parsers.versionerrortext constant in the
C implementation of the module.  Its presence can be used to determine
whether this behavior is present in a version of the module.  The value
of the constant is the leading text of the ImportError raised and is set
to "Python minor version mismatch".

Here is an example of what the new error looks like:

  Traceback (most recent call last):
    File "test.py", line 1, in <module>
      import mercurial.parsers
  ImportError: Python minor version mismatch: The Mercurial extension
  modules were compiled with Python 2.7.6, but Mercurial is currently using
  Python with sys.hexversion=33883888: Python 2.5.6
  (r256:88840, Nov 18 2012, 05:37:10)
  [GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))]
   at: /opt/local/Library/Frameworks/Python.framework/Versions/2.5/Resources/
    Python.app/Contents/MacOS/Python

The reason for raising an error in this scenario is that Python's C API
is known not to be compatible from minor version to minor version, even
if sys.api_version is the same.  See for example this Python bug report
about incompatibilities between 2.5 and 2.6+:

  http://bugs.python.org/issue8118

These incompatibilities can cause Mercurial to break in mysterious,
unforeseen ways.  For example, when Mercurial compiled with Python 2.7 was
run with 2.5, the following crash occurred when running "hg status":

  http://bz.selenic.com/show_bug.cgi?id=4110

After this crash was fixed, running with Python 2.5 no longer crashes, but
the following puzzling behavior still occurs:

    $ hg status
      ...
      File ".../mercurial/changelog.py", line 123, in __init__
        revlog.revlog.__init__(self, opener, "00changelog.i")
      File ".../mercurial/revlog.py", line 251, in __init__
        d = self._io.parseindex(i, self._inline)
      File ".../mercurial/revlog.py", line 158, in parseindex
        index, cache = parsers.parse_index2(data, inline)
    TypeError: data is not a string

which can be reproduced more simply with:

    import mercurial.parsers as parsers
    parsers.parse_index2("", True)

Both the crash and the TypeError occurred because the Python C API's
PyString_Check() returns the wrong value when the C header files from
Python 2.7 are run with Python 2.5.  This is an example of an
incompatibility of the sort mentioned in the Python bug report above.

Failing fast with an informative error message results in a better user
experience in cases like the above.  The information in the ImportError
also simplifies troubleshooting for those on Mercurial mailing lists, the
bug tracker, etc.

This patch only adds the version check to parsers.c, which is sufficient
to affect command-line commands like "hg status" and "hg summary".
An idea for a future improvement is to move the version-checking C code
to a more central location, and have it run when importing all
Mercurial extension modules and not just parsers.c.

test branch selection options

  $ hg init branch
  $ cd branch
  $ hg branch a
  marked working directory as branch a
  (branches are permanent and global, did you want a bookmark?)
  $ echo a > foo
  $ hg ci -d '0 0' -Ama
  adding foo
  $ echo a2 > foo
  $ hg ci -d '0 0' -ma2
  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg branch c
  marked working directory as branch c
  (branches are permanent and global, did you want a bookmark?)
  $ echo c > foo
  $ hg ci -d '0 0' -mc
  $ hg tag -l z
  $ cd ..
  $ hg clone -r 0 branch branch2
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  updating to branch a
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd branch2
  $ hg up 0
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg branch b
  marked working directory as branch b
  (branches are permanent and global, did you want a bookmark?)
  $ echo b > foo
  $ hg ci -d '0 0' -mb
  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg --encoding utf-8 branch æ
  marked working directory as branch \xc3\xa6 (esc)
  (branches are permanent and global, did you want a bookmark?)
  $ echo ae1 > foo
  $ hg ci -d '0 0' -mae1
  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg --encoding utf-8 branch -f æ
  marked working directory as branch \xc3\xa6 (esc)
  (branches are permanent and global, did you want a bookmark?)
  $ echo ae2 > foo
  $ hg ci -d '0 0' -mae2
  created new head
  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg branch -f b
  marked working directory as branch b
  (branches are permanent and global, did you want a bookmark?)
  $ echo b2 > foo
  $ hg ci -d '0 0' -mb2
  created new head

unknown branch and fallback

  $ hg in -qbz
  abort: unknown branch 'z'!
  [255]
  $ hg in -q ../branch#z
  2:f25d57ab0566
  $ hg out -qbz
  abort: unknown branch 'z'!
  [255]

in rev c branch a

  $ hg in -qr c ../branch#a
  1:dd6e60a716c6
  2:f25d57ab0566
  $ hg in -qr c -b a
  1:dd6e60a716c6
  2:f25d57ab0566

out branch .

  $ hg out -q ../branch#.
  1:b84708d77ab7
  4:65511d0e2b55
  $ hg out -q -b .
  1:b84708d77ab7
  4:65511d0e2b55

out branch . non-ascii

  $ hg --encoding utf-8 up æ
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg --encoding latin1 out -q ../branch#.
  2:df5a44224d4e
  3:4f4a5125ca10
  $ hg --encoding latin1 out -q -b .
  2:df5a44224d4e
  3:4f4a5125ca10

clone branch b

  $ cd ..
  $ hg clone branch2#b branch3
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 1 files (+1 heads)
  updating to branch b
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg -q -R branch3 heads b
  2:65511d0e2b55
  1:b84708d77ab7
  $ hg -q -R branch3 parents
  2:65511d0e2b55
  $ rm -rf branch3

clone rev a branch b

  $ hg clone -r a branch2#b branch3
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 1 files (+1 heads)
  updating to branch a
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg -q -R branch3 heads b
  2:65511d0e2b55
  1:b84708d77ab7
  $ hg -q -R branch3 parents
  0:5b65ba7c951d
  $ rm -rf branch3