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Re: [PATCH 11/22] qapi/parser: Rework _check_pragma_list_of_str as a Typ
From: |
Markus Armbruster |
Subject: |
Re: [PATCH 11/22] qapi/parser: Rework _check_pragma_list_of_str as a TypeGuard |
Date: |
Sun, 25 Apr 2021 14:32:06 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) |
John Snow <jsnow@redhat.com> writes:
> TypeGuards wont exist in Python proper until 3.10. Ah well. We can hack
> up our own by declaring this function to return the type we claim it
> checks for and using this to safely downcast object -> List[str].
>
> In so doing, I bring this function in-line under _pragma so it can use
> the 'info' object in its closure. Having done this, _pragma also now
> no longer needs to take a 'self' parameter, so drop it.
>
> Rename it to just _check(), to help us out with the line-length -- and
> now that it's contained within _pragma, it is contextually easier to see
> how it's used anyway -- especially with types.
>
> Signed-off-by: John Snow <jsnow@redhat.com>
>
> ---
>
> I left (name, value) as args to avoid creating a fully magic "macro",
> though, I thought this was too weird:
>
> info.pragma.foobar = _check()
>
> and it looked more reasonable as:
>
> info.pragma.foobar = _check(name, value)
>
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
> scripts/qapi/parser.py | 26 +++++++++++++-------------
> 1 file changed, 13 insertions(+), 13 deletions(-)
>
> diff --git a/scripts/qapi/parser.py b/scripts/qapi/parser.py
> index 16fd36f8391..d02a134aae9 100644
> --- a/scripts/qapi/parser.py
> +++ b/scripts/qapi/parser.py
> @@ -17,6 +17,7 @@
> from collections import OrderedDict
> import os
> import re
> +from typing import List
>
> from .common import match_nofail
> from .error import QAPISemError, QAPISourceError
> @@ -151,28 +152,27 @@ def _include(include, info, incl_fname,
> previously_included):
> ) from err
>
> @staticmethod
> - def _check_pragma_list_of_str(name, value, info):
> - if (not isinstance(value, list)
> - or any([not isinstance(elt, str) for elt in value])):
> - raise QAPISemError(
> - info,
> - "pragma %s must be a list of strings" % name)
> + def _pragma(name, value, info):
> +
> + def _check(name, value) -> List[str]:
> + if (not isinstance(value, list) or
> + any([not isinstance(elt, str) for elt in value])):
> + raise QAPISemError(
> + info,
> + "pragma %s must be a list of strings" % name)
> + return value
>
> - def _pragma(self, name, value, info):
> if name == 'doc-required':
> if not isinstance(value, bool):
> raise QAPISemError(info,
> "pragma 'doc-required' must be boolean")
> info.pragma.doc_required = value
> elif name == 'command-name-exceptions':
> - self._check_pragma_list_of_str(name, value, info)
> - info.pragma.command_name_exceptions = value
> + info.pragma.command_name_exceptions = _check(name, value)
> elif name == 'command-returns-exceptions':
> - self._check_pragma_list_of_str(name, value, info)
> - info.pragma.command_returns_exceptions = value
> + info.pragma.command_returns_exceptions = _check(name, value)
> elif name == 'member-name-exceptions':
> - self._check_pragma_list_of_str(name, value, info)
> - info.pragma.member_name_exceptions = value
> + info.pragma.member_name_exceptions = _check(name, value)
> else:
> raise QAPISemError(info, "unknown pragma '%s'" % name)
While I appreciate the terseness, I'm not sure I like the generic name
_check() for checking one of two special cases, namely "list of string".
The other case being "boolean". We could acquire more cases later.
- Re: [PATCH 07/22] qapi/parser: assert object keys are strings, (continued)
[PATCH 12/22] qapi/parser: add type hint annotations, John Snow, 2021/04/21
[PATCH 02/22] qapi/source: [RFC] add "with_column" contextmanager, John Snow, 2021/04/21
[PATCH 11/22] qapi/parser: Rework _check_pragma_list_of_str as a TypeGuard, John Snow, 2021/04/21
- Re: [PATCH 11/22] qapi/parser: Rework _check_pragma_list_of_str as a TypeGuard,
Markus Armbruster <=
[PATCH 15/22] qapi/parser: allow 'ch' variable name, John Snow, 2021/04/21
[PATCH 16/22] qapi/parser: add docstrings, John Snow, 2021/04/21
[PATCH 10/22] qapi/parser: Fix typing of token membership tests, John Snow, 2021/04/21