On 2/24/21 7:32 AM, Markus Armbruster wrote:
John Snow <js...@redhat.com> writes:
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".
We don't need to assert that something is a str if we've already checked
that it is -- use a cast instead for these cases.
Signed-off-by: John Snow <js...@redhat.com>
Reviewed-by: Eduardo Habkost <ehabk...@redhat.com>
Reviewed-by: Cleber Rosa <cr...@redhat.com>
---
scripts/qapi/expr.py | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/scripts/qapi/expr.py b/scripts/qapi/expr.py
index afa6bd07769..f45d6be1f4c 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 MutableMapping, Optional
+from typing import MutableMapping, Optional, cast
from .common import c_name
from .error import QAPISemError
@@ -232,7 +232,7 @@ 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']
I believe you need this only so you can declare check_type()'s
allow_dict to be Optional[str]. More busy-work around allow_dict...
I'm tempted to ask for allow_dict: Any and call it a day.
You're right, this is because of the signature for the allow_dict
argument. Ultimately, the pragma is a collection of strings and we need
to prove we are looking up a string somewhere or other.
(Or tell the type checker to leave us alone.)
Unfortunately, the "check" in check_exprs falls off almost immediately.
Working with dictly-typed objects is a little annoying for this reason.
This works for now; but finding a better way to do the pragma checks is
probably the more correct thing. (And not something I really want to try
and get through review until we're done typing, I think.)
check_type(members, info, "'data'", allow_dict=name)
@@ -240,7 +240,7 @@ 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']
Likwewise.
@@ -337,7 +337,7 @@ def check_exprs(exprs):
else:
raise QAPISemError(info, "expression is missing metatype")
- name = expr[meta]
+ name = cast(str, expr[meta]) # Asserted right below:
"Checked", not "asserted".
Oh, yes.
check_name_is_str(name, info, "'%s'" % meta)
info.set_defn(meta, name)
check_defn_name_str(name, info, meta)
Cast before check gives me a queasy feeling. It's lying to the type
checker.
Hamfisted way to avoid lying:
check_name_is_str(expr[meta], ...)
name = cast(str, expr[meta])
Something like
name = check_name_is_str(name, ...)
might be neater, but then we'd have to find a better function name.
OK, I'll look into re-ordering this.
