Re: [PATCH v3 02/16] qapi/expr.py: Check for dict instead of OrderedDict

From: Markus Armbruster <armbru@redhat.com>
To: John Snow <jsnow@redhat.com>
Cc: Michael Roth <michael.roth@amd.com>,
	Cleber Rosa <crosa@redhat.com>,
	qemu-devel@nongnu.org, Eduardo Habkost <ehabkost@redhat.com>
Subject: Re: [PATCH v3 02/16] qapi/expr.py: Check for dict instead of OrderedDict
Date: Wed, 24 Feb 2021 10:30:12 +0100	[thread overview]
Message-ID: <87a6rt7qzf.fsf@dusky.pond.sub.org> (raw)
In-Reply-To: <20210223003408.964543-3-jsnow@redhat.com> (John Snow's message of "Mon, 22 Feb 2021 19:33:54 -0500")

John Snow <jsnow@redhat.com> writes:

> OrderedDict is a subtype of dict, so we can check for a more general
> form. These functions do not themselves depend on it being any
> particular type.

True.  The actual arguments can only be OrderedDict, though.  I think we
refrained from relaxing to dict in these helpers because we felt
"staying ordered" is clearer.

We're *this* close to mooting the point, because

    Changed in version 3.7: Dictionary order is guaranteed to be
    insertion order. This behavior was an implementation detail of
    CPython from 3.6.

https://docs.python.org/3.7/library/stdtypes.html

Is messing with it necessary for later work?  If not, is it a worthwhile
improvement?

> 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 35695c4c653..5694c501fa3 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)