diff mbox series

[v4,06/23] qapi/schema: declare type for QAPISchemaObjectTypeMember.type

Message ID 20240313044127.49089-7-jsnow@redhat.com (mailing list archive)
State New, archived
Headers show
Series qapi: statically type schema.py | expand

Commit Message

John Snow March 13, 2024, 4:41 a.m. UTC 
A QAPISchemaObjectTypeMember's type gets resolved only during .check().
We have QAPISchemaObjectTypeMember.__init__() initialize self.type =
None, and .check() assign the actual type.  Using .type before .check()
is wrong, and hopefully crashes due to the value being None.  Works.

However, it makes for awkward typing.  With .type:
Optional[QAPISchemaType], mypy is of course unable to see that it's None
before .check(), and a QAPISchemaType after.  To help it over the hump,
we'd have to assert self.type is not None before all the (valid) uses.
The assertion catches invalid uses, but only at run time; mypy can't
flag them.

Instead, declare .type in .__init__() as QAPISchemaType *without*
initializing it.  Using .type before .check() now certainly crashes,
which is an improvement.  Mypy still can't flag invalid uses, but that's
okay.

Addresses typing errors such as these:

qapi/schema.py:657: error: "None" has no attribute "alternate_qtype"  [attr-defined]
qapi/schema.py:662: error: "None" has no attribute "describe"  [attr-defined]

Signed-off-by: John Snow <jsnow@redhat.com>
---
 scripts/qapi/schema.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index da273c1649d..8440a7243d8 100644
--- a/scripts/qapi/schema.py
+++ b/scripts/qapi/schema.py
@@ -786,7 +786,7 @@  def __init__(self, name, info, typ, optional, ifcond=None, features=None):
             assert isinstance(f, QAPISchemaFeature)
             f.set_defined_in(name)
         self._type_name = typ
-        self.type = None
+        self.type: QAPISchemaType  # set during check()
         self.optional = optional
         self.features = features or []