Re: [PATCH v4 06/14] qapi/introspect.py: replace 'extra' dict with 'comment' argument

[John Snow]

On 2/3/21 9:23 AM, Markus Armbruster wrote:
> John Snow <jsnow@redhat.com> writes:
>
> > This is only used to pass in a dictionary with a comment already set, so
> > skip the runaround and just accept the comment.
> >
> > This works because _tree_to_qlit() treats 'if': None; 'comment': None
> > exactly like absent 'if'; 'comment'.
>
> Confusing, because the two paragraphs talk about two different things:
>
> 1. Actual arguments for @extra are either None or {'comment': comment}.
>     Simplify: replace parameter @extra by parameter @comment.
>
> 2. Dumb down the return value to always be of the form
>
>      (obj {'if': ifcond, 'comment': comment})

I think you are drawing attention to the fact that 'if' and 'comment' 
are now always present in this dict instead of conditionally present.

(else, I have misread you. (I think you are missing a comma.))

> I suspect splitting the patch is easier than crafting a clear commit
> message for the combined one.

I wouldn't have considered to break out such a small change into two 
even smaller changes, but as you are in charge here ... Okey Dokey.

(meta-tangent: [1])

> > Signed-off-by: John Snow <jsnow@redhat.com>
> > ---
> >   scripts/qapi/introspect.py | 18 ++++++++++--------
> >   1 file changed, 10 insertions(+), 8 deletions(-)
> >
> > diff --git a/scripts/qapi/introspect.py b/scripts/qapi/introspect.py
> > index d3fbf694ad2..0aa3b77109f 100644
> > --- a/scripts/qapi/introspect.py
> > +++ b/scripts/qapi/introspect.py
> > @@ -10,6 +10,8 @@
> >   See the COPYING file in the top-level directory.
> >   """
> >   
> > +from typing import Optional
> > +
> >   from .common import (
> >       c_name,
> >       gen_endif,
> > @@ -24,11 +26,11 @@
> >   )
> >   
> >   
> > -def _make_tree(obj, ifcond, extra=None):
> > -    if extra is None:
> > -        extra = {}
> > -    if ifcond:
> > -        extra['if'] = ifcond
> > +def _make_tree(obj, ifcond, comment=None):
> > +    extra = {
> > +        'if': ifcond,
> > +        'comment': comment,
> > +    }
> >       return (obj, extra)
>
> Obvious way to do just 1.:
>
>     def _make_tree(obj, ifcond, comment=None):
>         extra = {}
>         if ifcond:
>             extra['if'] = ifcond
>         if comment:
>             extra['comment'] = comment

OK.

> >   
> >   
> > @@ -174,18 +176,18 @@ def _gen_features(features):
> >           return [_make_tree(f.name, f.ifcond) for f in features]
> >   
> >       def _gen_tree(self, name, mtype, obj, ifcond, features):
> > -        extra = None
> > +        comment: Optional[str] = None
> >           if mtype not in ('command', 'event', 'builtin', 'array'):
> >               if not self._unmask:
> >                   # Output a comment to make it easy to map masked names
> >                   # back to the source when reading the generated output.
> > -                extra = {'comment': '"%s" = %s' % (self._name(name), name)}
> > +                comment = f'"{self._name(name)}" = {name}'
> >               name = self._name(name)
> >           obj['name'] = name
> >           obj['meta-type'] = mtype
> >           if features:
> >               obj['features'] = self._gen_features(features)
> > -        self._trees.append(_make_tree(obj, ifcond, extra))
> > +        self._trees.append(_make_tree(obj, ifcond, comment))
> >   
> >       def _gen_member(self, member):
> >           obj = {'name': member.name, 'type': self._use_type(member.type)}


[1] As a matter of process, I sometimes find it cumbersome to 
intentionally engineer an intermediary state when I jumped straight from 
A->C in my actual editing.

I will usually keep such intermediary forms when they come about 
naturally in the course of development, but rarely seek to add them 
artificially -- it feels like a major bummer to engineer, test, and 
scrutinize code that's only bound to be deleted immediately after. 
Sometimes, it feels like a waste of reviewer effort, too.

It's been years and I still don't think I have any real intuitive sense 
for this, which is ...unfortunate.

--js