view tests/test-convert-cvs-detectmerge.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 config convert.cvsps.mergefrom config setting.
(Should test similar mergeto feature, but I don't understand it yet.)
Requires builtin cvsps.

  $ "$TESTDIR/hghave" cvs || exit 80
  $ CVSROOT=`pwd`/cvsrepo
  $ export CVSROOT

  $ cvscall()
  > {
  >     cvs -f "$@"
  > }

output of 'cvs ci' varies unpredictably, so just discard it
XXX copied from test-convert-cvs-synthetic

  $ cvsci()
  > {
  >     sleep 1
  >     cvs -f ci "$@" > /dev/null
  > }

XXX copied from test-convert-cvs-synthetic

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "convert = " >> $HGRCPATH
  $ echo "[convert]" >> $HGRCPATH
  $ echo "cvsps.cache=0" >> $HGRCPATH
  $ echo "cvsps.mergefrom=\[MERGE from (\S+)\]" >> $HGRCPATH

create cvs repository with one project

  $ mkdir cvsrepo
  $ cvscall -q -d "$CVSROOT" init
  $ mkdir cvsrepo/proj

populate cvs repository

  $ cvscall -Q co proj
  $ cd proj
  $ touch file1
  $ cvscall -Q add file1
  $ cvsci -m"add file1 on trunk"
  cvs commit: Examining .

create two release branches

  $ cvscall -q tag -b v1_0
  T file1
  $ cvscall -q tag -b v1_1
  T file1

modify file1 on branch v1_0

  $ cvscall -Q update -rv1_0
  $ sleep 1
  $ echo "change" >> file1
  $ cvsci -m"add text"
  cvs commit: Examining .

make unrelated change on v1_1

  $ cvscall -Q update -rv1_1
  $ touch unrelated
  $ cvscall -Q add unrelated
  $ cvsci -m"unrelated change"
  cvs commit: Examining .

merge file1 to v1_1

  $ cvscall -Q update -jv1_0
  RCS file: $TESTTMP/cvsrepo/proj/file1,v
  retrieving revision 1.1
  retrieving revision 1.1.2.1
  Merging differences between 1.1 and 1.1.2.1 into file1
  $ cvsci -m"add text [MERGE from v1_0]"
  cvs commit: Examining .

merge change to trunk

  $ cvscall -Q update -A
  $ cvscall -Q update -jv1_1
  RCS file: $TESTTMP/cvsrepo/proj/file1,v
  retrieving revision 1.1
  retrieving revision 1.1.4.1
  Merging differences between 1.1 and 1.1.4.1 into file1
  $ cvsci -m"add text [MERGE from v1_1]"
  cvs commit: Examining .

non-merged change on trunk

  $ echo "foo" > file2
  $ cvscall -Q add file2
  $ cvsci -m"add file2 on trunk" file2

this will create rev 1.3
change on trunk to backport

  $ echo "backport me" >> file1
  $ cvsci -m"add other text" file1
  $ cvscall log file1
  
  RCS file: $TESTTMP/cvsrepo/proj/file1,v
  Working file: file1
  head: 1.3
  branch:
  locks: strict
  access list:
  symbolic names:
  	v1_1: 1.1.0.4
  	v1_0: 1.1.0.2
  keyword substitution: kv
  total revisions: 5;	selected revisions: 5
  description:
  ----------------------------
  revision 1.3
  date: * (glob)
  add other text
  ----------------------------
  revision 1.2
  date: * (glob)
  add text [MERGE from v1_1]
  ----------------------------
  revision 1.1
  date: * (glob)
  branches:  1.1.2;  1.1.4;
  add file1 on trunk
  ----------------------------
  revision 1.1.4.1
  date: * (glob)
  add text [MERGE from v1_0]
  ----------------------------
  revision 1.1.2.1
  date: * (glob)
  add text
  =============================================================================

XXX how many ways are there to spell "trunk" with CVS?
backport trunk change to v1_1

  $ cvscall -Q update -rv1_1
  $ cvscall -Q update -j1.2 -j1.3 file1
  RCS file: $TESTTMP/cvsrepo/proj/file1,v
  retrieving revision 1.2
  retrieving revision 1.3
  Merging differences between 1.2 and 1.3 into file1
  $ cvsci -m"add other text [MERGE from HEAD]" file1

fix bug on v1_1, merge to trunk with error

  $ cvscall -Q update -rv1_1
  $ echo "merge forward" >> file1
  $ cvscall -Q tag unmerged
  $ cvsci -m"fix file1"
  cvs commit: Examining .
  $ cvscall -Q update -A
  $ cvscall -Q update -junmerged -jv1_1
  RCS file: $TESTTMP/cvsrepo/proj/file1,v
  retrieving revision 1.1.4.2
  retrieving revision 1.1.4.3
  Merging differences between 1.1.4.2 and 1.1.4.3 into file1

note the typo in the commit log message

  $ cvsci -m"fix file1 [MERGE from v1-1]"
  cvs commit: Examining .
  $ cvs -Q tag -d unmerged

convert to hg

  $ cd ..
  $ hg convert proj proj.hg
  initializing destination proj.hg repository
  connecting to $TESTTMP/cvsrepo
  scanning source...
  collecting CVS rlog
  12 log entries
  creating changesets
  warning: CVS commit message references non-existent branch 'v1-1':
  fix file1 [MERGE from v1-1]
  10 changeset entries
  sorting...
  converting...
  9 add file1 on trunk
  8 unrelated change
  7 add text
  6 add text [MERGE from v1_0]
  5 add text [MERGE from v1_1]
  4 add file2 on trunk
  3 add other text
  2 add other text [MERGE from HEAD]
  1 fix file1
  0 fix file1 [MERGE from v1-1]

complete log

  $ template="{rev}: '{branches}' {desc}\n"
  $ hg -R proj.hg log --template="$template"
  9: '' fix file1 [MERGE from v1-1]
  8: 'v1_1' fix file1
  7: 'v1_1' add other text [MERGE from HEAD]
  6: '' add other text
  5: '' add file2 on trunk
  4: '' add text [MERGE from v1_1]
  3: 'v1_1' add text [MERGE from v1_0]
  2: 'v1_0' add text
  1: 'v1_1' unrelated change
  0: '' add file1 on trunk

graphical log

  $ hg -R proj.hg log -G --template="$template"
  o  9: '' fix file1 [MERGE from v1-1]
  |
  | o  8: 'v1_1' fix file1
  | |
  | o  7: 'v1_1' add other text [MERGE from HEAD]
  |/|
  o |  6: '' add other text
  | |
  o |  5: '' add file2 on trunk
  | |
  o |  4: '' add text [MERGE from v1_1]
  |\|
  | o    3: 'v1_1' add text [MERGE from v1_0]
  | |\
  +---o  2: 'v1_0' add text
  | |
  | o  1: 'v1_1' unrelated change
  |/
  o  0: '' add file1 on trunk