[Distutils] [Python-Dev] distlib updated with resources API

[David Cournapeau]

On Mon, Oct 1, 2012 at 12:40 AM, Donald Stufft <donald.stufft at gmail.com> wrote:
> On Sunday, September 30, 2012 at 6:50 PM, David Cournapeau wrote:
>
> I am not sure I understand the argument: whatever the syntax, if the
> feature is there, you will have the same problem ? The fact that it is
> used by existing solutions tend to convince me it is not a problem
> (cabal works much better than distutils/etc... in pretty much every
> way, including installing things with dependency from their package
> servers, not to speak about RPM).
>
> I have a site that pulls data from python packages, one of my problems
> of late has been pulling requirements data out of a setuptools setup.py.
> Simply
> fetching the data for my current system is simple, however because of the
> use
> of conditionals that affect the final outcome of the metadata in order to
> make sure I get a true and complete accounting of all the metadata I would
> have to anticipate every combination of conditions used inside that file.
>
> Now as far as I can tell, the bento.info conditionals have that same problem
> except that they have a much narrow scope, so they have a smaller matrix.
>
> How would I given a package that has an ``if os(windows)`` conditional, get
> a representation of that files metadata as if it were in windows? I would
> need
> to override what os(windows) is? Now if this same package also has
> conditonals
> for flags, the matrix becomes larger and larger and I need to either create
> my own custom parser that just ignores or annotates the conditionals or I
> need
> to use the official parser and run it through once per item in the matrix to
> get
> the "whole story". Am I incorrect in that?
>
> Additionally, conditionals as they are (to my understanding, having never
> used bento but having read the docs and some of it's source code)
> implemented
> in bento complicate the parser and confuse reading a file with understanding
> a file.
>
> What additional power or benefit does:
>
> Library:
>     InstallRequires:
>         docutils,
>         sphinx
>         if os(windows):
>             pywin32
>
> provide over:
>
> {
>     "Library": {
>         "InstallRequires": [
>             "docutils",
>             "sphinx",
>             "pywin32; sys.playform == win32"
>         ]
>     }
> }

It is obviously exactly the same, it is just different syntax (which
is why I don't understand the "fetching requirements" arguments, since
whatever is true for bento is true of your format and vice et versa).

>
> Maybe i'm missing some powerful construct in the bento.info that warrants
> throwing out a lot of hard work and testing of a lot of individuals for
> these
> common formats, however I just don't see it in merely providing a simple
> conditional statement. The ``bento.parser`` package contains ~1700 SLOC
> now without investigating that terribly deeply I'm willing to bet almost all
> of that could be thrown out in the use of a standard format.

What I am afraid of is that one will need to add a lots of those
markers, not just for requirements, which will lose the point of using
a common format. I would also recommend against json, because it does
not allow for comments, yaml is much better in that regard.

> I know you've mentioned Cabal a lot when talking about bento, and it's
> obvious it's been a very big influence on your design.

Mostly the syntax, actually.

David