[Distutils] buildout: overriding the global [versions] section

[Leonardo Rochael Almeida]

Hi,

It seems I cannot override, for a single buildout part, the version
information of the global [versions] section.

Is this possible and I just overlooked something?

If not, I intend to add support for that on zc.recipe.egg and/or
z3c.recipe.scripts recipes.

Any comments?

And where can I find the source for z3c.recipe.scripts?

More details below:

I've frequently found myself in the situation of needing to install,
on the same buildout, different parts containing eggs with conflicting
version requirements.

It would be useful if I could specify a version information that
overrode the global [versions] information, in a part with a
zc.recipe.egg or z3c.recipe.scripts recipe.

Notice that specifying the version on the 'eggs' setting doesn't work
to override the global [versions] specification. I.e., the following
buildout.cfg:

  [buildout]
  parts =
    testbrower

  versions=versions

  [versions]
  zope.testbrowser=3.6.0a2

  [testbrower]
  recipe = zc.recipe.egg
  eggs =
    zope.testbrowser==3.11.1
-------

Fails with:

  The version, 3.6.0a2, is not consistent with the requirement,
'zope.testbrowser==3.11.1'.
  While:
    Installing testbrower.
  Error: Bad version 3.6.0a2

What would be nice is if I could say something like:

  [buildout]
  parts =
    testbrower

  versions=versions

  [versions]
  zope.testbrowser=3.6.0a2

  [testbrowser-versions]
  zope.testbrowser=3.11.1

  [testbrower]
  recipe = zc.recipe.egg
  versions = testbrowser-versions
  eggs =
    zope.testbrowser
-------

Or maybe even:

  (...)
  [testbrower]
  recipe = zc.recipe.egg
  versions =
    zope.testbrowser = 3.11.1
  eggs =
    zope.testbrowser
-------

And then have buildout pick my version override only while installing
the eggs in that part.

The buildout easy_install API can already [1] accept a local version
specification in the 'versions' keyword to the
zc.buildout.easy_install.install() function. It also specifies that
the global version specification can be retrieved and modified through
the zc.buildout.easy_install.default_versions() function.

[1] http://pypi.python.org/pypi/zc.buildout/1.5.2#specifying-version-information-independent-of-requirements

However, the docs don't say what happens if both a default_versions()
is set and a "versions=" keyword is passed to .install() containing
conflicting information.

In a worse case scenario, I could save the results of
zc.buildout.easy_install.default_versions() and restore after calling
.install() with the overridden versions.

Any comments, for or against?

Jim?

Cheers,

Leo