Add mypy-plugin extra dependency (#1605)

* Add mypy-plugin extra dependency

use `pip install classes[mypy-plugin]` for installin additional
dependencies required by the mypy-plugin.
Add mypy-plugin extra dependency

use `pip install classes[mypy-plugin]` for installing additional
dependencies required by the mypy-plugin.

* Remove mypy from dev deps

---------

Co-authored-by: sobolevn <mail@sobolevn.me>

Author: zhukovgreen

.github/workflows/test.yml

@@ -50,7 +50,7 @@ jobs:
     - name: Install dependencies
       run: |
         poetry config virtualenvs.in-project true
-        poetry install
+        poetry install --extras=compatible-mypy
 
         poetry run pip install -U pip
 

README.md

@@ -40,6 +40,11 @@ You are also required to [configure](https://returns.readthedocs.io/en/latest/pa
 `mypy` correctly and install our plugin
 to fix [this existing issue](https://github.com/python/mypy/issues/3157):
 
+```bash
+pip install returns[compatible-mypy]
+```
+and
+
 ```ini
 # In setup.cfg or mypy.ini:
 [mypy]

poetry.lock

@@ -48,14 +48,14 @@ _ = "returns.contrib.hypothesis._entrypoint"
 python = "^3.7"
 
 typing-extensions = ">=4.0,<5.0"
+mypy = { version = "^1.4.0", optional = true }
 
 [tool.poetry.dev-dependencies]
 anyio = "^3.7"
 trio = "^0.22"
 attrs = "^23.1"
 httpx = "^0.24"
 
-mypy = "^1.4"
 wemake-python-styleguide = "^0.17"
 flake8-pytest-style = "^1.6"
 flake8-pyi = "^23.4"
@@ -81,6 +81,9 @@ doc8 = "^1.0"
 m2r2 = "^0.3"
 tomlkit = "^0.11"
 
+[tool.poetry.extras]
+compatible-mypy = ["mypy"]
+
 
 [build-system]
 requires = ["poetry-core>=1.5.0"]