Re: [PATCH] schemas: Add vim modeline

[Daniel P . Berrangé]

On Thu, Jul 30, 2020 at 01:51:10PM +0200, Markus Armbruster wrote:
> Daniel P. Berrangé <berrange@redhat.com> writes:
> 
> >                               modify them so that we can load the 
> > files straight into the python intepretor as code, and not parse 
> > them as data. I feel unhappy about treating data as code though.
> 
> Stress on *can* load.  Doesn't mean we should.
> 
> Ancient prior art: Lisp programs routinely use s-expressions as
> configuration file syntax.  They don't load them as code, they read them
> as data.
> 
> With Python, it's ast.parse(), I think.

Yes, that could work


> > struct: ImageInfoSpecificQCow2
> > data:
> >   compat: str
> >   "*data-file": str
> >   "*data-file-raw": bool
> >   "*lazy-refcounts": bool
> >   "*corrupt": bool
> >   refcount-bits: int
> >   "*encrypt": ImageInfoSpecificQCow2Encryption
> >   "*bitmaps":
> >     - Qcow2BitmapInfo
> >   compression-type: Qcow2CompressionType
> >
> >
> > Then we could use a regular off the shelf YAML parser in python.
> >
> > The uglyiness with quotes is due to the use of "*". Slightly less ugly
> > if we simply declare that quotes are always used, even where they're
> > not strictly required.
> 
> StrictYAML insists on quotes.

I wouldn't suggest StrictYAML, just normal YAML is what pretty much
everyone uses.

If we came up with a different way to mark a field as optional
instead of using the magic "*" then we wouldn't need to quote
anything

> I hate having to quote identifiers.  There's a reason we don't write
> 
>     'int'
>     'main'('int', 'argc', 'char' *'argv'[])
>     {
>         'printf'("hello world\n");
>         return 0;
>     }
> 
> > struct: ImageInfoSpecificQCow2
> > data:
> >   "compat": "str"
> >   "*data-file": "str"
> >   "*data-file-raw": "bool"
> >   "*lazy-refcounts": "bool"
> >   "*corrupt": "bool"
> >   "refcount-bits": "int"
> >   "*encrypt": "ImageInfoSpecificQCow2Encryption"
> >   "*bitmaps":
> >     - "Qcow2BitmapInfo"
> >   "compression-type": "Qcow2CompressionType"
> >
> > With the use of "---" to denote the start of document, we have no trouble 
> > parsing our files which would actually be a concatenation of multiple 
> > documents. The python YAML library provides the easy yaml.load_all()
> > method.
> 
> Required reading on YAML:
> https://www.arp242.net/yaml-config.html

I don't think this is especially helpful to our evaluation. You can write
such blog posts about pretty much any thing if you want to pick holes in a
proposal. Certainly there's plenty of awful stuff you can write about
JSON, and Python.

> Some of the criticism there doesn't matter for our use case.

Yeah, what matters is whether it can do the job we need in a way that is
better than what we have today, and whether there are any further options
to consider that might be viable alternatives.

Regards,
Daniel
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