view tests/test-clone-r.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.

  $ hg init test
  $ cd test

  $ echo 0 >> afile
  $ hg add afile
  $ hg commit -m "0.0"

  $ echo 1 >> afile
  $ hg commit -m "0.1"

  $ echo 2 >> afile
  $ hg commit -m "0.2"

  $ echo 3 >> afile
  $ hg commit -m "0.3"

  $ hg update -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ echo 1 >> afile
  $ hg commit -m "1.1"
  created new head

  $ echo 2 >> afile
  $ hg commit -m "1.2"

  $ echo a line > fred
  $ echo 3 >> afile
  $ hg add fred
  $ hg commit -m "1.3"
  $ hg mv afile adifferentfile
  $ hg commit -m "1.3m"

  $ hg update -C 3
  1 files updated, 0 files merged, 2 files removed, 0 files unresolved

  $ hg mv afile anotherfile
  $ hg commit -m "0.3m"

  $ hg debugindex -f 1 afile
     rev flag   offset   length     size  .....   link     p1     p2       nodeid (re)
       0 0000        0        3        2  .....      0     -1     -1 362fef284ce2 (re)
       1 0000        3        5        4  .....      1      0     -1 125144f7e028 (re)
       2 0000        8        7        6  .....      2      1     -1 4c982badb186 (re)
       3 0000       15        9        8  .....      3      2     -1 19b1fc555737 (re)

  $ hg debugindex adifferentfile
     rev    offset  length  ..... linkrev nodeid       p1           p2 (re)
       0         0      75  .....       7 2565f3199a74 000000000000 000000000000 (re)

  $ hg debugindex anotherfile
     rev    offset  length  ..... linkrev nodeid       p1           p2 (re)
       0         0      75  .....       8 2565f3199a74 000000000000 000000000000 (re)

  $ hg debugindex fred
     rev    offset  length  ..... linkrev nodeid       p1           p2 (re)
       0         0       8  .....       6 12ab3bcc5ea4 000000000000 000000000000 (re)

  $ hg debugindex --manifest
     rev    offset  length  ..... linkrev nodeid       p1           p2 (re)
       0         0      48  .....       0 43eadb1d2d06 000000000000 000000000000 (re)
       1        48      48  .....       1 8b89697eba2c 43eadb1d2d06 000000000000 (re)
       2        96      48  .....       2 626a32663c2f 8b89697eba2c 000000000000 (re)
       3       144      48  .....       3 f54c32f13478 626a32663c2f 000000000000 (re)
       4       192      ..  .....       6 de68e904d169 626a32663c2f 000000000000 (re)
       5       2..      68  .....       7 09bb521d218d de68e904d169 000000000000 (re)
       6       3..      54  .....       8 1fde233dfb0f f54c32f13478 000000000000 (re)

  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  4 files, 9 changesets, 7 total revisions

  $ cd ..

  $ for i in 0 1 2 3 4 5 6 7 8; do
  >   echo
  >   echo ---- hg clone -r "$i" test test-"$i"
  >   hg clone -r "$i" test test-"$i"
  >   cd test-"$i"
  >   hg verify
  >   cd ..
  > done
  
  ---- hg clone -r 0 test test-0
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 1 changesets, 1 total revisions
  
  ---- hg clone -r 1 test test-1
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 1 files
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 2 changesets, 2 total revisions
  
  ---- hg clone -r 2 test test-2
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 1 files
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 3 changesets, 3 total revisions
  
  ---- hg clone -r 3 test test-3
  adding changesets
  adding manifests
  adding file changes
  added 4 changesets with 4 changes to 1 files
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 4 changesets, 4 total revisions
  
  ---- hg clone -r 4 test test-4
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 1 files
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 2 changesets, 2 total revisions
  
  ---- hg clone -r 5 test test-5
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 3 changes to 1 files
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 3 changesets, 3 total revisions
  
  ---- hg clone -r 6 test test-6
  adding changesets
  adding manifests
  adding file changes
  added 4 changesets with 5 changes to 2 files
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  2 files, 4 changesets, 5 total revisions
  
  ---- hg clone -r 7 test test-7
  adding changesets
  adding manifests
  adding file changes
  added 5 changesets with 6 changes to 3 files
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  3 files, 5 changesets, 6 total revisions
  
  ---- hg clone -r 8 test test-8
  adding changesets
  adding manifests
  adding file changes
  added 5 changesets with 5 changes to 2 files
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  2 files, 5 changesets, 5 total revisions

  $ cd test-8
  $ hg pull ../test-7
  pulling from ../test-7
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 4 changesets with 2 changes to 3 files (+1 heads)
  (run 'hg heads' to see heads, 'hg merge' to merge)
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  4 files, 9 changesets, 7 total revisions
  $ cd ..