[Distutils] [Python-Dev] How we can get rid of eggs for 2.6 and beyond

[M.-A. Lemburg]

On 2008-03-21 22:21, Phillip J. Eby wrote:
> At 08:06 PM 3/21/2008 +0100, M.-A. Lemburg wrote:
>> I guess the only way to support all of these variants is
>> to use a filesystem based approach, e.g. by placing a file
>> with a special extension into some dir on sys.path.
>> The "database" logic could then scan sys.path for these
>> files, read the data and provide an interface to it.
>>
>> All bdist formats would then have to include these files.
> 
> That's the idea behind the current version of PEP 262, yes, and I think 
> it should be kept.
> 
>> A separate FILES section also doesn't seem to be necessary -
>> we could just add one or more entries or the format:
>>
>> CreatesDir abc/
>> CreatesFile abc/xyz1.py
>> CreatesDir abc/def/
>> CreatesFile abc/def/xyz2.py
>> CreatesFile abc/def/xyz3.py
>> CreatesFile abc/def/xyz4.ini
> 
> I actually think the size and hash information is good, in order to be 
> able to tell if you're looking at an original file.  I'm not sure how 
> useful the permissions and uid/gid info is.  I'm hoping we'll hear from 
> anybody who has a use case for that.

You're heading off in the wrong direction: we should not be trying
to rewrite RPM or InnoSetup in Python.

Anything more complicated should be left to tools which are
specifically written to manage complex software setups.

I honestly believe that most people would be happy if we just
provide these two things (and no more):

  * install a package from a local archive, a URL or PyPI

  * uninstall a package in way that doesn't break other
    installed packages

and whatever the mechanism, avoid making any undercover
changes to the Python installation such as adding
.pth files, overriding site.py, etc. - these are
not needed if the tool keeps to the simple task of
installing and uninstalling Python packages.

Examples:

python pypi.py install mypkg-1.0.tgz
python pypi.py install http://www.example.com/mypkg-1.0.tgz
python pypi.py install mypkg-1.0

python pypi.py uninstall mypkg

If there's a dependency problem, the tool should print the
list of other packages it needs. It should not try to install
things automagically.

If a package needs other modules as well, the package docs
can point the user to use e.g.

python pypi.py install mydep1-1.3 mydep2-2.3 mydep4-0.3 mypkg-1.0

instead.

Anything more complicated should be left to specialized
tools such as RPM, apt, MSI or the other such tools out
there - after all the tool should be about Python *package*
installation, not application installation.

We *don't* need the tool to:

  * support multiple versions of a package (that's just bound
    to cause problems with pickle, isinstance() etc.)

  * provide namespace hacking (is a completely separate issue
    and can be handled by the packages rather than the install
    tool)

  * support all kinds of funky version numbers (if a package
    wants to participate in the system, the author better
    make sure that the version string fits the standard format)

  * provide some form of intra-package bus interface (ie.
    "entry points" as you call them)

  * provide support for keeping whole packages in ZIP files
    (doesn't play well with C extensions, clutters up the
    sys.path, is read-only, needs special importers, etc. etc. )

  * try automatic version matching for required packages

  * download things from SourceForge or other sites with special
    download mechanisms

  * scan websites for links

  * make coffee, clean the house, send the kids to school :-)

> And of course, there are still some issues to be resolved regarding 
> requirements, package name/version stuff, etc.  But we can hash those 
> out once we reach a quorum on the Distutils-SIG.

-- 
Marc-Andre Lemburg
eGenix.com

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