Re: [PATCH v2 02/16] qapi/expr.py: Check for dict instead of OrderedDict

[John Snow]

On 11/17/20 1:08 PM, Eduardo Habkost wrote:
> On Tue, Nov 17, 2020 at 05:30:04PM +0100, Markus Armbruster wrote:
> > John Snow <jsnow@redhat.com> writes:
> >
> > > OrderedDict is a subtype of dict, so we can check for a more general form.
> > >
> > > Signed-off-by: John Snow <jsnow@redhat.com>
> > > Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
> > > Reviewed-by: Cleber Rosa <crosa@redhat.com>
> > > ---
> > >   scripts/qapi/expr.py | 5 ++---
> > >   1 file changed, 2 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/scripts/qapi/expr.py b/scripts/qapi/expr.py
> > > index 35695c4c653b..5694c501fa38 100644
> > > --- a/scripts/qapi/expr.py
> > > +++ b/scripts/qapi/expr.py
> > > @@ -14,7 +14,6 @@
> > >   # This work is licensed under the terms of the GNU GPL, version 2.
> > >   # See the COPYING file in the top-level directory.
> > >   
> > > -from collections import OrderedDict
> > >   import re
> > >   
> > >   from .common import c_name
> > > @@ -131,7 +130,7 @@ def check_if_str(ifcond):
> > >   
> > >   
> > >   def normalize_members(members):
> > > -    if isinstance(members, OrderedDict):
> > > +    if isinstance(members, dict):
> > >           for key, arg in members.items():
> > >               if isinstance(arg, dict):
> > >                   continue
> > > @@ -162,7 +161,7 @@ def check_type(value, info, source,
> > >       if not allow_dict:
> > >           raise QAPISemError(info, "%s should be a type name" % source)
> > >   
> > > -    if not isinstance(value, OrderedDict):
> > > +    if not isinstance(value, dict):
> > >           raise QAPISemError(info,
> > >                              "%s should be an object or type name" % source)
> >
> > Plain dict remembers insertion order since Python 3.6, but it wasn't
> > formally promised until 3.7.
> >
> > Can we simply ditch OrderedDict entirely?
>
> In theory, our build requirement is "Python >= 3.6", not
> "CPython >= 3.6".  In practice, I don't expect anybody to ever
> use any other Python implementation except CPython to build QEMU.
>
> I think we can get rid of OrderedDict if you really want to.

No harm in keeping it right now either, it doesn't make typing harder. 
The OrderedDict is created in the parser, so we can cover ditching 
OrderedDict when we get to that module if desired.

--js