view tests/test-import-eol.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 > makepatch.py <<EOF
  > f = file('eol.diff', 'wb')
  > w = f.write
  > w('test message\n')
  > w('diff --git a/a b/a\n')
  > w('--- a/a\n')
  > w('+++ b/a\n')
  > w('@@ -1,5 +1,5 @@\n')
  > w(' a\n')
  > w('-bbb\r\n')
  > w('+yyyy\r\n')
  > w(' cc\r\n')
  > w(' \n')
  > w(' d\n')
  > w('-e\n')
  > w('\ No newline at end of file\n')
  > w('+z\r\n')
  > w('\ No newline at end of file\r\n')
  > EOF

  $ hg init repo
  $ cd repo
  $ echo '\.diff' > .hgignore


Test different --eol values

  $ python -c 'file("a", "wb").write("a\nbbb\ncc\n\nd\ne")'
  $ hg ci -Am adda
  adding .hgignore
  adding a
  $ python ../makepatch.py


invalid eol

  $ hg --config patch.eol='LFCR' import eol.diff
  applying eol.diff
  abort: unsupported line endings type: LFCR
  [255]
  $ hg revert -a


force LF

  $ hg --traceback --config patch.eol='LF' import eol.diff
  applying eol.diff
  $ cat a
  a
  yyyy
  cc
  
  d
  e (no-eol)
  $ hg st


force CRLF

  $ hg up -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg --traceback --config patch.eol='CRLF' import eol.diff
  applying eol.diff
  $ cat a
  a\r (esc)
  yyyy\r (esc)
  cc\r (esc)
  \r (esc)
  d\r (esc)
  e (no-eol)
  $ hg st


auto EOL on LF file

  $ hg up -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg --traceback --config patch.eol='auto' import eol.diff
  applying eol.diff
  $ cat a
  a
  yyyy
  cc
  
  d
  e (no-eol)
  $ hg st


auto EOL on CRLF file

  $ python -c 'file("a", "wb").write("a\r\nbbb\r\ncc\r\n\r\nd\r\ne")'
  $ hg commit -m 'switch EOLs in a'
  $ hg --traceback --config patch.eol='auto' import eol.diff
  applying eol.diff
  $ cat a
  a\r (esc)
  yyyy\r (esc)
  cc\r (esc)
  \r (esc)
  d\r (esc)
  e (no-eol)
  $ hg st


auto EOL on new file or source without any EOL

  $ python -c 'file("noeol", "wb").write("noeol")'
  $ hg add noeol
  $ hg commit -m 'add noeol'
  $ python -c 'file("noeol", "wb").write("noeol\r\nnoeol\n")'
  $ python -c 'file("neweol", "wb").write("neweol\nneweol\r\n")'
  $ hg add neweol
  $ hg diff --git > noeol.diff
  $ hg revert --no-backup noeol neweol
  $ rm neweol
  $ hg --traceback --config patch.eol='auto' import -m noeol noeol.diff
  applying noeol.diff
  $ cat noeol
  noeol\r (esc)
  noeol
  $ cat neweol
  neweol
  neweol\r (esc)
  $ hg st


Test --eol and binary patches

  $ python -c 'file("b", "wb").write("a\x00\nb\r\nd")'
  $ hg ci -Am addb
  adding b
  $ python -c 'file("b", "wb").write("a\x00\nc\r\nd")'
  $ hg diff --git > bin.diff
  $ hg revert --no-backup b

binary patch with --eol

  $ hg import --config patch.eol='CRLF' -m changeb bin.diff
  applying bin.diff
  $ cat b
  a\x00 (esc)
  c\r (esc)
  d (no-eol)
  $ hg st
  $ cd ..