Add make_strawberry_decorator function

strawberry/decorator.py

@@ -0,0 +1,33 @@
+import functools
+
+from .resolvers import get_resolver_arguments
+from .utils.inspect import get_func_args
+
+
+def make_strawberry_decorator(func):
+    def decorator(resolver):
+        if hasattr(resolver, "_field_definition"):
+            raise Exception("Can't apply decorator after strawberry.field")  # TODO
+
+        function_args = get_func_args(resolver)
+
+        @functools.wraps(resolver)
+        def wrapped_resolver(source, info, **kwargs):
+            def wrapped(**kwargs):
+                # If resolver is another strawberry decorator then pass all the
+                # arguments to it
+                if getattr(resolver, "_strawberry_decorator", False):
+                    return resolver(source, info, **kwargs)
+
+                args, extra_kwargs = get_resolver_arguments(function_args, source, info)
+                return resolver(*args, **extra_kwargs, **kwargs)
+
+            # Call the decorator body with the original set of kwargs so that it
+            # has the opportunity to modify them
+            return func(wrapped, source, info=info, **kwargs)
+
+        wrapped_resolver._strawberry_decorator = True
+
+        return wrapped_resolver
+
+    return decorator

tests/test_decorator.py

@@ -0,0 +1,117 @@
+import strawberry
+from strawberry.decorator import make_strawberry_decorator
+
+
+def test_basic_decorator():
+    @make_strawberry_decorator
+    def upper_case(resolver, source, info, **kwargs):
+        result = resolver(**kwargs)
+        return result.upper()
+
+    @strawberry.type
+    class Query:
+        @strawberry.field
+        @upper_case
+        def greeting() -> str:
+            return "hi"
+
+    schema = strawberry.Schema(query=Query)
+    result = schema.execute_sync("query { greeting }")
+
+    assert not result.errors
+    assert result.data == {"greeting": "HI"}
+
+
+def test_decorator_with_arguments():
+    def suffix(value):
+        @make_strawberry_decorator
+        def wrapper(resolver, source, info, **kwargs):
+            result = resolver(**kwargs)
+            return f"{result}{value}"
+
+        return wrapper
+
+    @strawberry.type
+    class Query:
+        @strawberry.field
+        @suffix(" 👋")
+        def greeting() -> str:
+            return "hi"
+
+    schema = strawberry.Schema(query=Query)
+    result = schema.execute_sync("query { greeting }")
+
+    assert not result.errors
+    assert result.data == {"greeting": "hi 👋"}
+
+
+def test_multiple_decorators():
+    @make_strawberry_decorator
+    def upper_case(resolver, source, info, **kwargs):
+        result = resolver(**kwargs)
+        return result.upper()
+
+    def suffix(value):
+        @make_strawberry_decorator
+        def wrapper(resolver, source, info, **kwargs):
+            result = resolver(**kwargs)
+            return f"{result}{value}"
+
+        return wrapper
+
+    @strawberry.type
+    class Query:
+        @strawberry.field
+        @suffix(" 👋")
+        @upper_case
+        def greeting() -> str:
+            return "hi"
+
+    schema = strawberry.Schema(query=Query)
+    result = schema.execute_sync("query { greeting }")
+
+    assert not result.errors
+    assert result.data == {"greeting": "HI 👋"}
+
+
+def test_decorator_with_graphql_arguments():
+    @make_strawberry_decorator
+    def upper_case(resolver, source, info, **kwargs):
+        result = resolver(**kwargs)
+        return result.upper()
+
+    @strawberry.type
+    class Query:
+        @strawberry.field
+        @upper_case
+        def greeting(name: str) -> str:
+            return f"hi {name}"
+
+    schema = strawberry.Schema(query=Query)
+    result = schema.execute_sync('query { greeting(name: "everyone") }')
+
+    assert not result.errors
+    assert result.data == {"greeting": "HI EVERYONE"}
+
+
+def test_decorator_modify_argument():
+    def title_case_argument(argument_name):
+        @make_strawberry_decorator
+        def wrapped(resolver, source, info, **kwargs):
+            kwargs[argument_name] = kwargs[argument_name].title()
+            return resolver(**kwargs)
+
+        return wrapped
+
+    @strawberry.type
+    class Query:
+        @strawberry.field
+        @title_case_argument("name")
+        def greeting(name: str) -> str:
+            return f"hi {name}"
+
+    schema = strawberry.Schema(query=Query)
+    result = schema.execute_sync('query { greeting(name: "patrick") }')
+
+    assert not result.errors
+    assert result.data == {"greeting": "hi Patrick"}