Strawberry Exceptions
Strawberry defines its library-specific exceptions in strawberry.exceptions.
Strawberry Schema Exceptions
FieldWithResolverAndDefaultFactoryError
This exception is raised when strawberry.field is used with both resolver
and default_factory arguments.
@strawberry.typeclass Query: @strawberry.field(default_factory=lambda: "Example C") def c(self) -> str: return "I'm a resolver"
# Throws 'Field "c" on type "Query" cannot define a default_factory and a resolver.'FieldWithResolverAndDefaultValueError
This exception is raised when strawberry.field is used with both resolver
and default arguments.
def test_resolver() -> str: return "I'm a resolver"
@strawberry.typeclass Query: c: str = strawberry.field(default="Example C", resolver=test_resolver)
# Throws 'Field "c" on type "Query" cannot define a default value and a resolver.'MissingTypesForGenericError
This exception is raised when a Generic type is added to the Strawberry Schema without
passing any type to make it concrete.
MultipleStrawberryArgumentsError
This exception is raised when strawberry.argument is used multiple times in a type
annotation.
import strawberryfrom typing_extensions import Annotated
@strawberry.fielddef name( argument: Annotated[ str, strawberry.argument(description="This is a description"), strawberry.argument(description="Another description"), ]) -> str: return "Name"
# Throws 'Annotation for argument `argument` on field `name` cannot have multiple `strawberry.argument`s'UnsupportedTypeError
This exception is thrown when the type-annotation used is not supported by
strawberry.field. At the time of writing this exception is used by Pydantic
only
class Model(pydantic.BaseModel): field: pydantic.Json
@strawberry.experimental.pydantic.type(Model, fields=["field"])class Type: passWrongNumberOfResultsReturned
This exception is raised when the DataLoader returns a different number of results than requested.
async def idx(keys): return [1, 2]
loader = DataLoader(load_fn=idx)
await loader.load(1)
# Throws 'Received wrong number of results in dataloader, expected: 1, received: 2'Runtime exceptions
Some errors are also thrown when trying to exectuing queries (mutations or subscriptions).
MissingQueryError
This exception is raised when the request is missing the query parameter.
client.post("/graphql", data={})
# Throws 'Request data is missing a "query" value'UnallowedReturnTypeForUnion
This error is raised when the return type of a Union is not in the list of
Union types.
@strawberry.typeclass Outside: c: int
@strawberry.typeclass A: a: int
@strawberry.typeclass B: b: int
@strawberry.typeclass Mutation: @strawberry.mutation def hello(self) -> Union[A, B]: return Outside(c=5)
query = """
mutation {
hello {
__typename
... on A {
a
}
... on B {
b
}
}
}
"""
result = schema.execute_sync(query)# result will look like:# ExecutionResult(# data=None,# errors=[# GraphQLError(# "The type \"<class 'schema.Outside'>\" of the field \"hello\" is not in the list of the types of the union: \"['A', 'B']\"",# locations=[SourceLocation(line=3, column=9)],# path=["hello"],# )# ],# extensions={},# )WrongReturnTypeForUnion
This exception is thrown when the Union type cannot be resolved because it's not
a strawberry.field.
@strawberry.typeclass A: a: int
@strawberry.typeclass B: b: int
@strawberry.typeclass Query: ab: Union[A, B] = "ciao" # missing `strawberry.field` !
query = """{
ab {
__typename,
... on A {
a
}
}
}"""
result = schema.execute_sync(query, root_value=Query())
# result will look like:# ExecutionResult(# data=None,# errors=[# GraphQLError(# 'The type "<class \'str\'>" cannot be resolved for the field "ab" , are you using a strawberry.field?',# locations=[SourceLocation(line=2, column=9)],# path=["ab"],# )# ],# extensions={},# )