Define PartialType metaclass

RELEASED.md

@@ -0,0 +1,18 @@
+Release type: minor
+
+Add `PartialType` metaclass to make fields optional dynamically.
+
+```py
+from strawberry.tools import PartialType
+
+
+@strawberry.type
+class UserCreate:
+    firstname: str
+    lastname: str
+
+
+@strawberry.type
+class UserUpdate(UserCreate, metaclass=PartialType):
+    pass
+```

docs/guides/tools.md

@@ -94,4 +94,33 @@ type ComboQuery {
 }
 ```
 
+### `PartialType`
+
+`PartialType` metaclass is used to extend your type but makes its all field
+optional. Consider you have different types for each operation on the same model
+such as `UserCreate`, `UserUpdate` and `UserQuery`. `UserQuery` should have id
+field but the other does not. All fields of `UserQuery` and `UserUpdate` might
+be optional. In this case instead of defining the same field for each type one
+can define in a single type and extend it.
+
+```py
+from strawberry.tools import PartialType
+
+
+@strawberry.type
+class UserCreate:
+    firstname: str
+    lastname: str
+
+
+@strawberry.type
+class UserUpdate(UserCreate, metaclass=PartialType):
+    pass
+
+
+@strawberry.type
+class UserQuery(UserCreate, metaclass=PartialType):
+    id: Optional[strawberry.ID]
+```
+
 </CodeGrid>

strawberry/tools/__init__.py

@@ -1,7 +1,9 @@
 from .create_type import create_type
 from .merge_types import merge_types
+from .partialtype import PartialType
 
 __all__ = [
+    "PartialType",
     "create_type",
     "merge_types",
 ]

strawberry/tools/partialtype.py

@@ -0,0 +1,30 @@
+from abc import ABCMeta
+from typing import Optional
+
+import strawberry
+
+
+class PartialType(ABCMeta):
+    def __new__(cls, name: str, bases: tuple, namespaces: dict, **kwargs):
+        mro = super().__new__(cls, name, bases, namespaces, **kwargs).mro()
+        annotations = namespaces.get("__annotations__", {})
+        fields: list[str] = []
+        for base in mro[:-1]:  # the object class has no __annotations__ attr
+            for k, v in base.__annotations__.items():
+                # To prevent overriding the higher attr annotation
+                if k not in annotations:
+                    annotations[k] = v
+
+            fields.extend(field.name for field in base._type_definition.fields)
+
+        for field in annotations:
+            if not field.startswith("_"):
+                annotations[field] = Optional[annotations[field]]
+
+        namespaces["__annotations__"] = annotations
+        klass = super().__new__(cls, name, bases, namespaces, **kwargs)
+        for field in fields:
+            if not hasattr(klass, field):
+                setattr(klass, field, strawberry.UNSET)
+
+        return klass

tests/tools/test_partialtype.py

@@ -0,0 +1,68 @@
+import dataclasses
+
+import strawberry
+from strawberry.tools import PartialType
+from strawberry.type import StrawberryOptional
+
+
+def test_partialtype():
+    @strawberry.type
+    class RoleRead:
+        name: str
+        description: str
+
+    @strawberry.type
+    class UserRead:
+        firstname: str
+        lastname: str
+        role: RoleRead
+
+    @strawberry.input
+    class RoleInput(RoleRead):
+        pass
+
+    @strawberry.input
+    class UserQuery(UserRead, metaclass=PartialType):
+        role: RoleInput
+
+    read_firstname, read_lastname, read_role = UserRead._type_definition.fields
+
+    # user read type firstname field tests
+    assert read_firstname.python_name == "firstname"
+    assert read_firstname.graphql_name is None
+    assert read_firstname.default is dataclasses.MISSING
+    assert read_firstname.type is str
+
+    # user read type lastname field tests
+    assert read_lastname.python_name == "lastname"
+    assert read_lastname.graphql_name is None
+    assert read_lastname.default is dataclasses.MISSING
+    assert read_lastname.type is str
+
+    assert read_role.python_name == "role"
+    assert read_role.graphql_name is None
+    assert read_role.default is dataclasses.MISSING
+    assert read_role.type is RoleRead
+
+    query_firstname, query_lastname, query_role = UserQuery._type_definition.fields
+
+    # user query type firstname field tests
+    assert query_firstname.python_name == "firstname"
+    assert query_firstname.graphql_name is None
+    assert query_firstname.default is strawberry.UNSET
+    assert isinstance(query_firstname.type, StrawberryOptional)
+    assert query_firstname.type.of_type is str
+
+    # user query type lastname field tests
+    assert query_lastname.python_name == "lastname"
+    assert query_lastname.graphql_name is None
+    assert query_lastname.default is strawberry.UNSET
+    assert isinstance(query_lastname.type, StrawberryOptional)
+    assert query_lastname.type.of_type is str
+
+    # user query type role field tests
+    assert query_role.python_name == "role"
+    assert query_role.graphql_name is None
+    assert query_role.default is strawberry.UNSET
+    assert isinstance(query_role.type, StrawberryOptional)
+    assert query_role.type.of_type is RoleInput