Validate component usage (#23037)

* Update manifest validator

* Update circle

* Update text

* Typo

* fix link to codeowners

* Merge CODEOWNERS into hassfest

* Annotate errors with fixable

* Convert error to warning

* Lint

* Make abs path

* Python 3.5...

* Typo

* Fix tests

script/hassfest/codeowners.py

@@ -0,0 +1,85 @@
+"""Generate CODEOWNERS."""
+from typing import Dict
+
+from .model import Integration, Config
+
+BASE = """
+# This file is generated by script/manifest/codeowners.py
+# People marked here will be automatically requested for a review
+# when the code that they own is touched.
+# https://github.com/blog/2392-introducing-code-owners
+
+# Home Assistant Core
+setup.py @home-assistant/core
+homeassistant/*.py @home-assistant/core
+homeassistant/helpers/* @home-assistant/core
+homeassistant/util/* @home-assistant/core
+
+# Virtualization
+Dockerfile @home-assistant/docker
+virtualization/Docker/* @home-assistant/docker
+
+# Other code
+homeassistant/scripts/check_config.py @kellerza
+
+# Integrations
+""".strip()
+
+INDIVIDUAL_FILES = """
+# Individual files
+homeassistant/components/group/cover @cdce8p
+homeassistant/components/demo/weather @fabaff
+"""
+
+
+def generate_and_validate(integrations: Dict[str, Integration]):
+    """Generate CODEOWNERS."""
+    parts = [BASE]
+
+    for domain in sorted(integrations):
+        integration = integrations[domain]
+
+        if not integration.manifest:
+            continue
+
+        codeowners = integration.manifest['codeowners']
+
+        if not codeowners:
+            continue
+
+        for owner in codeowners:
+            if not owner.startswith('@'):
+                integration.add_error(
+                    'codeowners',
+                    'Code owners need to be valid GitHub handles.',
+                )
+
+        parts.append("homeassistant/components/{}/* {}".format(
+            domain, ' '.join(codeowners)))
+
+    parts.append('\n' + INDIVIDUAL_FILES.strip())
+
+    return '\n'.join(parts)
+
+
+def validate(integrations: Dict[str, Integration], config: Config):
+    """Validate CODEOWNERS."""
+    codeowners_path = config.root / 'CODEOWNERS'
+    config.cache['codeowners'] = content = generate_and_validate(integrations)
+
+    with open(str(codeowners_path), 'r') as fp:
+        if fp.read().strip() != content:
+            config.add_error(
+                "codeowners",
+                "File CODEOWNERS is not up to date. "
+                "Run python3 -m script.hassfest",
+                fixable=True
+            )
+        return
+
+
+def generate(integrations: Dict[str, Integration], config: Config):
+    """Generate CODEOWNERS."""
+    codeowners_path = config.root / 'CODEOWNERS'
+    with open(str(codeowners_path), 'w') as fp:
+        fp.write(config.cache['codeowners'] + '\n')