I tried to implement a --develop option for EasyInstall, but ran into a few
snags that forced me to rethink the option a bit.
Here's what I've settled on, that can actually be made to work. I'm adding
an --editable/-e option, which checks out or extracts a package to a
project-named subdirectory of the --build-directory.
Unlike the original concept of a "--develop" option, this does *not* run
the "develop" command on the checked out or extracted package. It simply
fetches and extracts it for you. The problem I had was that it's very
difficult to integrate the target package's setup script with the parent
easy_install command in order to maintain state properly between the
two. In particular, there's no way to tell if a setup script uses
setuptools or not, and no way to ensure that the setup script isn't going
to just modify stuff on its own, as some packages' setup scripts do. Using
the sandbox facility doesn't really help, since the "develop" command
*needs* to be able to write to the install directory. So, in the end, the
simplest thing was just to make it "--editable" and then you can go to the
directory and run "setup.py develop" yourself, which will also take care of
that package's dependencies. (Or of course you can run "easy_install ." to
install it normally, again with its dependencies.)
In order to use --editable, you must also specify a
--build-directory. Checked-out or extracted packages are copied into that
directory. If you specify --build-directory but not --editable, then if
there is already a package with the desired name in the build directory,
you'll just get a warning. But if you specify --editable and a package of
that name exists, you'll get an error message and an abort.
To use --editable, you must also specify only project names and versions on
the command line. If you want to download from a URL or filename, you must
specify it as a --find-links/-f value instead. (Note that this means you
need to tag checkout URLs with a "#egg=" suffix.)
Finally, if you want to force EasyInstall to check out a subversion URL
instead of a binary distribution, you'll need to ensure that you specify a
version that matches the checkout link. I recommend using
#egg=projectname-dev to tag links to development checkouts, so that people
can do::
easy_install -eb ~/projects projectname==dev
to specifically check out the development version in editable form to their
~/projects/projectname directory. The --editable flag causes easy_install
to only look for source distributions or checkouts, but a source
distribution will take precedence over a checkout if both match the
specified version.
All in all, there some caveats to using --editable, but that's mainly
because there aren't many #egg links out there yet, nor are conventions for
using them established as yet.
Anyway, this is all now in the CVS HEAD of setuptools; see EasyInstall.txt
for more docs and examples.
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