Errors installing some gems on Snow Leopard - libxml2

After upgrading to Snow Leopard, I found that installing some gems no longer worked, including webrat, mechanize etc. Each time I get this error:

checking for xmlParseDoc() in -lxml2... no
libxml2 is missing.  try 'port install libxml2' or 'yum install libxml2'
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

And no, I haven't tried installing it with macports, because I forswore macports a couple years back when I discovered I couldn't easily downgrade/manage ports. Since then, I have become very comfortable building from source by hand, and this is the first time I've run into something beyond my ken. I am willing to be persuaded to go back to macports, but only if there's no easy solution to this I am missing.

It doesn't appear that libxml2 is actually missing, just out of date perhaps?...

extended output

ERROR: Failed to build gem native extension.

/usr/local/bin/ruby extconf.rb
checking for iconv.h in /opt/local/include/,/opt/local/include/libxml2,/opt/local/include,/opt/local/include,/opt/local/include/libxml2,/usr/local/include,/usr/local/include/libxml2,/usr/local/include,/usr/local/include/libxml2,/usr/include,/usr/include/libxml2... yes
checking for libxml/parser.h in /opt/local/include/,/opt/local/include/libxml2,/opt/local/include,/opt/local/include,/opt/local/include/libxml2,/usr/local/include,/usr/local/include/libxml2,/usr/local/include,/usr/local/include/libxml2,/usr/include,/usr/include/libxml2... yes
checking for libxslt/xslt.h in /opt/local/include/,/opt/local/include/libxml2,/opt/local/include,/opt/local/include,/opt/local/include/libxml2,/usr/local/include,/usr/local/include/libxml2,/usr/local/include,/usr/local/include/libxml2,/usr/include,/usr/include/libxml2... yes
checking for libexslt/exslt.h in /opt/local/include/,/opt/local/include/libxml2,/opt/local/include,/opt/local/include,/opt/local/include/libxml2,/usr/local/include,/usr/local/include/libxml2,/usr/local/include,/usr/local/include/libxml2,/usr/include,/usr/include/libxml2... yes
checking for xmlParseDoc() in -lxml2... no
libxml2 is missing.  try 'port install libxml2' or 'yum install libxml2'
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers.  Check the mkmf.log file for more
details.  You may need configuration options.

Provided configuration options:
    --with-opt-dir
    --without-opt-dir
    --with-opt-include
    --without-opt-include=${opt-dir}/include
    --with-o开发者_如何学Gopt-lib
    --without-opt-lib=${opt-dir}/lib
    --with-make-prog
    --without-make-prog
    --srcdir=.
    --curdir
    --ruby=/usr/local/bin/ruby
    --with-iconv-dir
    --without-iconv-dir
    --with-iconv-include
    --without-iconv-include=${iconv-dir}/include
    --with-iconv-lib
    --without-iconv-lib=${iconv-dir}/lib
    --with-xml2-dir
    --without-xml2-dir
    --with-xml2-include
    --without-xml2-include=${xml2-dir}/include
    --with-xml2-lib
    --without-xml2-lib=${xml2-dir}/lib
    --with-xslt-dir
    --without-xslt-dir
    --with-xslt-include
    --without-xslt-include=${xslt-dir}/include
    --with-xslt-lib
    --without-xslt-lib=${xslt-dir}/lib
    --with-xml2lib
    --without-xml2lib


Gem files will remain installed in /usr/local/lib/ruby/gems/1.8/gems/nokogiri-1.4.1 for inspection.
Results logged to /usr/local/lib/ruby/gems/1.8/gems/nokogiri-1.4.1/ext/nokogiri/gem_make.out

floyd's solution is overkill - I had the same issue and started nuking some of the same /opt/local files related to xml2, but his 'find' command does not reveal the actual libxml2 files in opt/local/lib. It may be that you just need to nuke those.

Here are my nuked files:

/opt/local/include/libxml2
/opt/local/var/db/dports/distfiles/libxml2
/opt/local/var/db/dports/receipts/libxml2
/opt/local/var/db/dports/software/libxml2
/opt/local/var/db/dports/rsync.rsync.darwinports.org_dpupdate_dports/textproc/libxml2
/opt/local/share/gtk-doc/html/libxml2
/opt/local/var/db/dports/sources/rsync.rsync.darwinports.org_dpupdate_dports/textproc/libxml2

BUT before you try that - just nuke the lib files sudo rm /opt/local/lib/libxml2.*

When I tried to install after that it got into compiling it all but then barfed with an issue with libz...

So nuke that in /opt/local/lib sudo rm -rf /opt/local/lib/libz.*

And it compiles just fine!

So try nuking the /opt/local/lib libxml2.* and libz.* files, see if it compiles and if not, nuke the /opt/local/includes

UPDATE

As stated in another answer, the below solution is 'overkill' because it removes MacPorts from your system, which I thought I had already done earlier. Proceed carefully. There may be a way to use MacPorts to just update the libxml2 install.

I solved this problem (on my machine at least).

Once I realized that nothing in that trace suggested the lack of libxml2, but rather a problem with the version being detected, I looked around for confirmation of this fact. Sure enough, the nokogiri website (where many similar bug reports pointed me) states in no uncertain terms that Snow Leopard ships with a good working version of libxml2.

Thus, I reasoned that I must have installed a version by another means long ago. I would remember if I had installed by hand, so there was really only one option left, frickin' macports.

$ libxml2-2.7.1 tfwright$ sudo find / -type d -name "libxml2" 
find: /dev/fd/3: Not a directory
find: /dev/fd/4: Not a directory
/Developer/SDKs/MacOSX10.4u.sdk/usr/include/libxml2
/Developer/SDKs/MacOSX10.5.sdk/usr/include/libxml2
/Developer/SDKs/MacOSX10.6.sdk/usr/include/libxml2
/opt/local/include/libxml2
/opt/local/share/gtk-doc/html/libxml2
/opt/local/var/macports/distfiles/libxml2
/opt/local/var/macports/receipts/libxml2
/opt/local/var/macports/software/libxml2
/opt/local/var/macports/software/libxml2/2.6.30_0/opt/local/include/libxml2
/opt/local/var/macports/software/libxml2/2.6.30_0/opt/local/share/gtk-doc/html/libxml2
/opt/local/var/macports/sources/rsync.macports.org/release/ports/textproc/libxml2
/usr/include/libxml2
/usr/share/gtk-doc/html/libxml2

Son of a...just blowing away /opt/local/var/macports, which I tried first of all, didn't seem to fix the problem, so I went to the big guns.

sudo rm -rf \
/opt/local \
/Applications/DarwinPorts \
/Applications/MacPorts \
/Library/LaunchDaemons/org.macports.* \
/Library/Receipts/DarwinPorts*.pkg \
/Library/Receipts/MacPorts*.pkg \
/Library/StartupItems/DarwinPortsStartup \
/Library/Tcl/darwinports1.0 \
/Library/Tcl/macports1.0 \
~/.macports

After which, everything installs fine. that's right. Never trust the recommendations of error messages! Far from needing to reinstall libxml2 with macports, I needed to scrub away all traces of macports from my system, which was haunting me from beyond the trash.

The gems you are trying to install require libxml2. If you're comfortable installing from source, install libxml2.

You may run into dependency issues where libxml2 depends on a bunch of other packages that you'll need to build and install manually. That's one reason why macports ends up being useful.