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From: John Snow <jsnow@redhat.com>
To: Markus Armbruster <armbru@redhat.com>, qemu-devel@nongnu.org
Cc: Michael Roth <michael.roth@amd.com>, John Snow <jsnow@redhat.com>,
	Eduardo Habkost <ehabkost@redhat.com>,
	Cleber Rosa <crosa@redhat.com>
Subject: [PATCH v4 10/19] qapi/expr.py: Add casts in a few select cases
Date: Thu, 25 Mar 2021 02:03:47 -0400
Message-ID: <20210325060356.4040114-11-jsnow@redhat.com> (raw)
In-Reply-To: <20210325060356.4040114-1-jsnow@redhat.com>

Casts are instructions to the type checker only, they aren't "safe" and
should probably be avoided in general. In this case, when we perform
type checking on a nested structure, the type of each field does not
"stick".

(See PEP 647 for an example of "type narrowing" that does "stick".
 It is available in Python 3.10, so we can't use it yet.)

We don't need to assert that something is a str if we've already checked
or asserted that it is -- use a cast instead for these cases.

Signed-off-by: John Snow <jsnow@redhat.com>
---
 scripts/qapi/expr.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/scripts/qapi/expr.py b/scripts/qapi/expr.py
index ca5ab7bfda..505e67bd21 100644
--- a/scripts/qapi/expr.py
+++ b/scripts/qapi/expr.py
@@ -15,7 +15,7 @@
 # See the COPYING file in the top-level directory.
 
 import re
-from typing import Dict, Optional
+from typing import Dict, Optional, cast
 
 from .common import c_name
 from .error import QAPISemError
@@ -259,7 +259,7 @@ def check_enum(expr, info):
 
 
 def check_struct(expr, info):
-    name = expr['struct']
+    name = cast(str, expr['struct'])  # Asserted in check_exprs
     members = expr['data']
 
     check_type(members, info, "'data'", allow_dict=name)
@@ -267,7 +267,7 @@ def check_struct(expr, info):
 
 
 def check_union(expr, info):
-    name = expr['union']
+    name = cast(str, expr['union'])  # Asserted in check_exprs
     base = expr.get('base')
     discriminator = expr.get('discriminator')
     members = expr['data']
@@ -366,8 +366,8 @@ def check_exprs(exprs):
         else:
             raise QAPISemError(info, "expression is missing metatype")
 
-        name = expr[meta]
-        check_name_is_str(name, info, "'%s'" % meta)
+        check_name_is_str(expr[meta], info, "'%s'" % meta)
+        name = cast(str, expr[meta])
         info.set_defn(meta, name)
         check_defn_name_str(name, info, meta)
 
-- 
2.30.2



  parent reply index

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-25  6:03 [PATCH v4 00/19] qapi: static typing conversion, pt3 John Snow
2021-03-25  6:03 ` [PATCH v4 01/19] qapi/expr: Comment cleanup John Snow
2021-03-25 15:41   ` Markus Armbruster
2021-03-25 20:06     ` John Snow
2021-03-25  6:03 ` [PATCH v4 02/19] flake8: Enforce shorter line length for comments and docstrings John Snow
2021-03-25 15:21   ` Markus Armbruster
2021-03-25 20:20     ` John Snow
2021-03-26  6:26       ` Markus Armbruster
2021-03-26 16:30         ` John Snow
2021-03-26 16:44           ` Peter Maydell
2021-04-08  8:32             ` Markus Armbruster
2021-04-08  8:58             ` Daniel P. Berrangé
2021-04-09  9:33               ` Markus Armbruster
2021-04-09 17:08                 ` John Snow
2021-04-08  8:35           ` Markus Armbruster
2021-04-16 12:44   ` Markus Armbruster
2021-04-16 20:25     ` John Snow
2021-04-17 10:52       ` Markus Armbruster
2021-04-20 18:06         ` John Snow
2021-03-25  6:03 ` [PATCH v4 03/19] qapi/expr.py: Remove 'info' argument from nested check_if_str John Snow
2021-03-25  6:03 ` [PATCH v4 04/19] qapi/expr.py: Check for dict instead of OrderedDict John Snow
2021-03-25  6:03 ` [PATCH v4 05/19] qapi/expr.py: constrain incoming expression types John Snow
2021-03-25 14:04   ` Markus Armbruster
2021-03-25 20:48     ` John Snow
2021-03-26  5:40       ` Markus Armbruster
2021-03-26 17:12         ` John Snow
2021-03-25  6:03 ` [PATCH v4 06/19] qapi/expr.py: Add assertion for union type 'check_dict' John Snow
2021-03-25  6:03 ` [PATCH v4 07/19] qapi/expr.py: move string check upwards in check_type John Snow
2021-03-25  6:03 ` [PATCH v4 08/19] qapi: add tests for invalid 'data' field type John Snow
2021-03-25 14:24   ` Markus Armbruster
2021-03-25  6:03 ` [PATCH v4 09/19] qapi/expr.py: Check type of 'data' member John Snow
2021-03-25 14:26   ` Markus Armbruster
2021-03-25 21:04     ` John Snow
2021-03-25  6:03 ` John Snow [this message]
2021-03-25 14:33   ` [PATCH v4 10/19] qapi/expr.py: Add casts in a few select cases Markus Armbruster
2021-03-25 23:32     ` John Snow
2021-03-25  6:03 ` [PATCH v4 11/19] qapi/expr.py: Modify check_keys to accept any Collection John Snow
2021-03-25 14:45   ` Markus Armbruster
2021-03-25 23:37     ` John Snow
2021-03-25  6:03 ` [PATCH v4 12/19] qapi/expr.py: add type hint annotations John Snow
2021-03-25  6:03 ` [PATCH v4 13/19] qapi/expr.py: Consolidate check_if_str calls in check_if John Snow
2021-03-25 15:15   ` Markus Armbruster
2021-03-26  0:07     ` John Snow
2021-03-25  6:03 ` [PATCH v4 14/19] qapi/expr.py: Remove single-letter variable John Snow
2021-03-25  6:03 ` [PATCH v4 15/19] qapi/expr.py: enable pylint checks John Snow
2021-03-25  6:03 ` [PATCH v4 16/19] qapi/expr.py: Add docstrings John Snow
2021-04-14 15:04   ` Markus Armbruster
2021-04-17  1:00     ` John Snow
2021-04-17 13:18       ` Markus Armbruster
2021-04-21  1:27         ` John Snow
2021-04-21 13:58           ` Markus Armbruster
2021-04-21 18:20             ` John Snow
2021-03-25  6:03 ` [PATCH v4 17/19] qapi/expr.py: Use tuples instead of lists for static data John Snow
2021-03-25 15:19   ` Markus Armbruster
2021-03-25  6:03 ` [PATCH v4 18/19] qapi/expr.py: move related checks inside check_xxx functions John Snow
2021-03-25  6:03 ` [PATCH v4 19/19] qapi/expr.py: Use an expression checker dispatch table John Snow
2021-03-25 15:46 ` [PATCH v4 00/19] qapi: static typing conversion, pt3 Markus Armbruster
2021-03-26  0:40 ` John Snow
2021-03-26 18:01 ` John Snow

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