Have pylint warn when user visible log messages do not start with capital letter or end with a period (#48064)

Co-authored-by: Martin Hjelmare <marhje52@gmail.com>

pylint/plugins/hass_logger.py

@@ -0,0 +1,85 @@
+import astroid
+from pylint.checkers import BaseChecker
+from pylint.interfaces import IAstroidChecker
+
+LOGGER_NAMES = ("LOGGER", "_LOGGER")
+LOG_LEVEL_ALLOWED_LOWER_START = ("debug",)
+
+# This is our checker class.
+# Checkers should always inherit from `BaseChecker`.
+class HassLoggerFormatChecker(BaseChecker):
+    """Add class member attributes to the class locals dictionary."""
+
+    __implements__ = IAstroidChecker
+
+    # The name defines a custom section of the config for this checker.
+    name = "hass_logger"
+    priority = -1
+    msgs = {
+        "W0001": (
+            "User visible logger messages must not end with a period",
+            "hass-logger-period",
+            "Periods are not permitted at the end of logger messages",
+        ),
+        "W0002": (
+            "User visible logger messages must start with a capital letter or downgrade to debug",
+            "hass-logger-capital",
+            "All logger messages must start with a capital letter",
+        ),
+    }
+    options = (
+        (
+            "hass-logger",
+            {
+                "default": "properties",
+                "help": (
+                    "Validate _LOGGER or LOGGER messages conform to Home Assistant standards."
+                ),
+            },
+        ),
+    )
+
+    def visit_call(self, node):
+        """Called when a :class:`.astroid.node_classes.Call` node is visited.
+        See :mod:`astroid` for the description of available nodes.
+        :param node: The node to check.
+        :type node: astroid.node_classes.Call
+        """
+        if not isinstance(node.func, astroid.Attribute) or not isinstance(
+            node.func.expr, astroid.Name
+        ):
+            return
+
+        if not node.func.expr.name in LOGGER_NAMES:
+            return
+
+        if not node.args:
+            return
+
+        first_arg = node.args[0]
+
+        if not isinstance(first_arg, astroid.Const) or not first_arg.value:
+            return
+
+        log_message = first_arg.value
+
+        if len(log_message) < 1:
+            return
+
+        if log_message[-1] == ".":
+            self.add_message("hass-logger-period", args=node.args, node=node)
+
+        if (
+            isinstance(node.func.attrname, str)
+            and node.func.attrname not in LOG_LEVEL_ALLOWED_LOWER_START
+            and log_message[0].upper() != log_message[0]
+        ):
+            self.add_message("hass-logger-capital", args=node.args, node=node)
+
+
+def register(linter):
+    """This required method auto registers the checker.
+    :param linter: The linter to register the checker to.
+    :type linter: pylint.lint.PyLinter
+    """
+    linter.register_checker(HassLoggerFormatChecker(linter))