bpo-32505: dataclasses: raise TypeError if a member variable is of type Field, but doesn't have a type annotation. (GH-6192)
If a dataclass has a member variable that's of type Field, but it doesn't have a type annotation, raise TypeError.
diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py
index 41b5b5d..5d4d4a6 100644
--- a/Lib/dataclasses.py
+++ b/Lib/dataclasses.py
@@ -573,22 +573,6 @@
return f
-def _find_fields(cls):
- # Return a list of Field objects, in order, for this class (and no
- # base classes). Fields are found from the class dict's
- # __annotations__ (which is guaranteed to be ordered). Default
- # values are from class attributes, if a field has a default. If
- # the default value is a Field(), then it contains additional
- # info beyond (and possibly including) the actual default value.
- # Pseudo-fields ClassVars and InitVars are included, despite the
- # fact that they're not real fields. That's dealt with later.
-
- # If __annotations__ isn't present, then this class adds no new
- # annotations.
- annotations = cls.__dict__.get('__annotations__', {})
- return [_get_field(cls, name, type) for name, type in annotations.items()]
-
-
def _set_new_attribute(cls, name, value):
# Never overwrites an existing attribute. Returns True if the
# attribute already exists.
@@ -663,10 +647,25 @@
if getattr(b, _PARAMS).frozen:
any_frozen_base = True
+ # Annotations that are defined in this class (not in base
+ # classes). If __annotations__ isn't present, then this class
+ # adds no new annotations. We use this to compute fields that
+ # are added by this class.
+ # Fields are found from cls_annotations, which is guaranteed to be
+ # ordered. Default values are from class attributes, if a field
+ # has a default. If the default value is a Field(), then it
+ # contains additional info beyond (and possibly including) the
+ # actual default value. Pseudo-fields ClassVars and InitVars are
+ # included, despite the fact that they're not real fields.
+ # That's dealt with later.
+ cls_annotations = cls.__dict__.get('__annotations__', {})
+
# Now find fields in our class. While doing so, validate some
# things, and set the default values (as class attributes)
# where we can.
- for f in _find_fields(cls):
+ cls_fields = [_get_field(cls, name, type)
+ for name, type in cls_annotations.items()]
+ for f in cls_fields:
fields[f.name] = f
# If the class attribute (which is the default value for
@@ -685,6 +684,11 @@
else:
setattr(cls, f.name, f.default)
+ # Do we have any Field members that don't also have annotations?
+ for name, value in cls.__dict__.items():
+ if isinstance(value, Field) and not name in cls_annotations:
+ raise TypeError(f'{name!r} is a field but has no type annotation')
+
# Check rules that apply if we are derived from any dataclasses.
if has_dataclass_bases:
# Raise an exception if any of our bases are frozen, but we're not.