Improve mypy support for create_type

[patrick91]

MyPy unfortunately doesn't allow using classes created from functions as base classes, so
for example this code would fail:

import strawberry
from strawberry.tools import create_type

@strawberry.field
def name() -> str:
    return "foo"

MyType = create_type("MyType", [name])

class Query(MyType):
    ...

with this error:

E     main:10: error: Invalid base class "MyType"   (diff)
E     main:10: error: Variable "main.MyType" is not valid as a type (diff)
E     main:10: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases (diff)
E     main:13: note: Revealed type is "def (*_args: Any, **_kwds: Any) -> main.Query" (diff)

So I've changed the plugin to tell mypy that the return type is a type alias and it fixes the issue 😊

[codecov]

Codecov Report

Merging #1175 (a86f3c9) into main (d9ea4c3) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1175   +/-   ##
=======================================
  Coverage   97.45%   97.45%           
=======================================
  Files          88       88           
  Lines        3296     3296           
  Branches      473      473           
=======================================
  Hits         3212     3212           
  Misses         46       46           
  Partials       38       38           

[botberry]

Thanks for adding the RELEASE.md file!

Here's a preview of the changelog:

---

This releases fixes a MyPy issue that prevented from using types created with
create_type as base classes. This is now allowed and doesn't throw any error:

import strawberry
from strawberry.tools import create_type

@strawberry.field
def name() -> str:
    return "foo"

MyType = create_type("MyType", [name])

class Query(MyType):
    ...

---

Here's the preview release card for twitter:

Here's the tweet text:

🆕 Release (next) is out! Thanks to Patrick Arminio for the PR 👏

Get it here 👉 https://github.com/strawberry-graphql/strawberry/releases/tag/(next)

[botberry]

Thanks for adding the RELEASE.md file!

Here's a preview of the changelog:

---

This releases fixes a MyPy issue that prevented from using types created with
create_type as base classes. This is now allowed and doesn't throw any error:

import strawberry
from strawberry.tools import create_type

@strawberry.field
def name() -> str:
    return "foo"

MyType = create_type("MyType", [name])

class Query(MyType):
    ...

---

Here's the preview release card for twitter:

Here's the tweet text:

🆕 Release (next) is out! Thanks to Patrick Arminio for the PR 👏

Get it here 👉 https://github.com/strawberry-graphql/strawberry/releases/tag/(next)