view tests/test-rebase-rename.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.

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > rebase=
  > 
  > [alias]
  > tlog  = log  --template "{rev}: '{desc}' {branches}\n"
  > tglog = tlog --graph
  > EOF


  $ hg init a
  $ cd a

  $ mkdir d
  $ echo a > a
  $ hg ci -Am A
  adding a

  $ echo b > d/b
  $ hg ci -Am B
  adding d/b

  $ hg mv d d-renamed
  moving d/b to d-renamed/b (glob)
  $ hg ci -m 'rename B'

  $ hg up -q -C 1

  $ hg mv a a-renamed
  $ echo x > d/x
  $ hg add d/x

  $ hg ci -m 'rename A'
  created new head

  $ hg tglog
  @  3: 'rename A'
  |
  | o  2: 'rename B'
  |/
  o  1: 'B'
  |
  o  0: 'A'
  

Rename is tracked:

  $ hg tlog -p --git -r tip
  3: 'rename A' 
  diff --git a/a b/a-renamed
  rename from a
  rename to a-renamed
  diff --git a/d/x b/d/x
  new file mode 100644
  --- /dev/null
  +++ b/d/x
  @@ -0,0 +1,1 @@
  +x
  
Rebase the revision containing the rename:

  $ hg rebase -s 3 -d 2
  saved backup bundle to $TESTTMP/a/.hg/strip-backup/*-backup.hg (glob)

  $ hg tglog
  @  3: 'rename A'
  |
  o  2: 'rename B'
  |
  o  1: 'B'
  |
  o  0: 'A'
  

Rename is not lost:

  $ hg tlog -p --git -r tip
  3: 'rename A' 
  diff --git a/a b/a-renamed
  rename from a
  rename to a-renamed
  diff --git a/d-renamed/x b/d-renamed/x
  new file mode 100644
  --- /dev/null
  +++ b/d-renamed/x
  @@ -0,0 +1,1 @@
  +x
  

Rebased revision does not contain information about b (issue3739)

  $ hg log -r 3 --debug
  changeset:   3:032a9b75e83bff1dcfb6cbfa4ef50a704bf1b569
  tag:         tip
  phase:       draft
  parent:      2:220d0626d185f372d9d8f69d9c73b0811d7725f7
  parent:      -1:0000000000000000000000000000000000000000
  manifest:    3:035d66b27a1b06b2d12b46d41a39adb7a200c370
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  files+:      a-renamed d-renamed/x
  files-:      a
  extra:       branch=default
  extra:       rebase_source=73a3ee40125d6f0f347082e5831ceccb3f005f8a
  description:
  rename A
  
  

  $ cd ..


  $ hg init b
  $ cd b

  $ echo a > a
  $ hg ci -Am A
  adding a

  $ echo b > b
  $ hg ci -Am B
  adding b

  $ hg cp b b-copied
  $ hg ci -Am 'copy B'

  $ hg up -q -C 1

  $ hg cp a a-copied
  $ hg ci -m 'copy A'
  created new head

  $ hg tglog
  @  3: 'copy A'
  |
  | o  2: 'copy B'
  |/
  o  1: 'B'
  |
  o  0: 'A'
  
Copy is tracked:

  $ hg tlog -p --git -r tip
  3: 'copy A' 
  diff --git a/a b/a-copied
  copy from a
  copy to a-copied
  
Rebase the revision containing the copy:

  $ hg rebase -s 3 -d 2
  saved backup bundle to $TESTTMP/b/.hg/strip-backup/*-backup.hg (glob)

  $ hg tglog
  @  3: 'copy A'
  |
  o  2: 'copy B'
  |
  o  1: 'B'
  |
  o  0: 'A'
  

Copy is not lost:

  $ hg tlog -p --git -r tip
  3: 'copy A' 
  diff --git a/a b/a-copied
  copy from a
  copy to a-copied
  

Rebased revision does not contain information about b (issue3739)

  $ hg log -r 3 --debug
  changeset:   3:98f6e6dbf45ab54079c2237fbd11066a5c41a11d
  tag:         tip
  phase:       draft
  parent:      2:39e588434882ff77d01229d169cdc77f29e8855e
  parent:      -1:0000000000000000000000000000000000000000
  manifest:    3:2232f329d66fffe3930d43479ae624f66322b04d
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  files+:      a-copied
  extra:       branch=default
  extra:       rebase_source=0a8162ff18a8900df8df8ef7ac0046955205613e
  description:
  copy A
  
  

  $ cd ..


Test rebase across repeating renames:

  $ hg init repo

  $ cd repo

  $ echo testing > file1.txt
  $ hg add file1.txt
  $ hg ci -m "Adding file1"

  $ hg rename file1.txt file2.txt
  $ hg ci -m "Rename file1 to file2"

  $ echo Unrelated change > unrelated.txt
  $ hg add unrelated.txt
  $ hg ci -m "Unrelated change"

  $ hg rename file2.txt file1.txt
  $ hg ci -m "Rename file2 back to file1"

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

  $ echo Another unrelated change >> unrelated.txt
  $ hg ci -m "Another unrelated change"
  created new head

  $ hg tglog
  @  4: 'Another unrelated change'
  |
  | o  3: 'Rename file2 back to file1'
  |/
  o  2: 'Unrelated change'
  |
  o  1: 'Rename file1 to file2'
  |
  o  0: 'Adding file1'
  

  $ hg rebase -s 4 -d 3
  saved backup bundle to $TESTTMP/repo/.hg/strip-backup/*-backup.hg (glob)

  $ hg diff --stat -c .
   unrelated.txt |  1 +
   1 files changed, 1 insertions(+), 0 deletions(-)

  $ cd ..