Mypy setup fixes (#27825)

* Install our core dependencies for mypy in azure

To match local setups and tox.

* Use "system" mypy in pre-commit instead of the "real" mypy hook

The results of mypy depend on what is installed. And the mypy hook
runs in a virtualenv of its own, meaning we'd need to install and
maintain another set of our dependencies there... no. Use the "system"
one and reuse the environment that is set up anyway already instead.

* Reintroduce needed ruamel.yaml type ignore

This ignore is required when ruamel.yaml is installed, and we want it
to be as it's part of the core dependency set.

.pre-commit-config.yaml

@@ -13,9 +13,17 @@ repos:
         additional_dependencies:
           - flake8-docstrings==1.3.1
           - pydocstyle==4.0.0
--   repo: https://github.com/pre-commit/mirrors-mypy.git
-    rev: v0.730
+# Using a local "system" mypy instead of the mypy hook, because its
+# results depend on what is installed. And the mypy hook runs in a
+# virtualenv of its own, meaning we'd need to install and maintain
+# another set of our dependencies there... no. Use the "system" one
+# and reuse the environment that is set up anyway already instead.
+-   repo: local
     hooks:
     -   id: mypy
-        args: []
+        name: mypy
+        entry: mypy
+        language: system
+        types: [python]
+        require_serial: true
         exclude: ^script/scaffold/templates/

azure-pipelines-ci.yml

@@ -174,12 +174,12 @@ stages:
     steps:
     - template: templates/azp-step-cache.yaml@azure
       parameters:
-        keyfile: 'requirements_test.txt | homeassistant/package_constraints.txt'
+        keyfile: 'requirements_test.txt | setup.py | homeassistant/package_constraints.txt'
         build: |
           python -m venv venv
 
           . venv/bin/activate
-          pip install -r requirements_test.txt -c homeassistant/package_constraints.txt
+          pip install -e . -r requirements_test.txt -c homeassistant/package_constraints.txt
     - script: |
         . venv/bin/activate
         mypy homeassistant

homeassistant/util/ruamel_yaml.py

@@ -90,7 +90,7 @@ def load_yaml(fname: str, round_trip: bool = False) -> JSON_TYPE:
     if round_trip:
         yaml = YAML(typ="rt")
         # type ignore: https://bitbucket.org/ruamel/yaml/pull-requests/42
-        yaml.preserve_quotes = True
+        yaml.preserve_quotes = True  # type: ignore
     else:
         if ExtSafeConstructor.name is None:
             ExtSafeConstructor.name = fname