Python doesn't have anything quite exactly like Traits, Interfaces, or
Mixins; but we can approximate it.
Add a 'Visitable' class that enforces a type signature for the visit()
method; this way, mypy is ensuring that even for otherwise unrelated
classes that do not inherit from a common base, this signature will
always be forced to be compatible.
Signed-off-by: John Snow <js...@redhat.com>
---
scripts/qapi/schema.py | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index 51af0449f5..55434f5c82 100644
--- a/scripts/qapi/schema.py
+++ b/scripts/qapi/schema.py
@@ -25,7 +25,13 @@
from .parser import QAPISchemaParser
-class QAPISchemaEntity:
+class Visitable:
+ """Abstract duck that suggests a class is visitable."""
+ def visit(self, visitor: 'QAPISchemaVisitor') -> None:
+ raise NotImplementedError
+
+
+class QAPISchemaEntity(Visitable):
meta: Optional[str] = None
def __init__(self, name: str, info, doc, ifcond=None, features=None):
@@ -136,7 +142,7 @@ def visit_event(self, name, info, ifcond, features,
arg_type, boxed):
pass
-class QAPISchemaModule:
+class QAPISchemaModule(Visitable):
def __init__(self, name):
self.name = name
self._entity_list = []
@@ -812,7 +818,7 @@ def visit(self, visitor):
self.arg_type, self.boxed)
-class QAPISchema:
+class QAPISchema(Visitable):
def __init__(self, fname):
self.fname = fname
parser = QAPISchemaParser(fname)
--
2.26.2
