Add pylint checker for CONNECTION_CLASS in config flows (#183937)

Co-authored-by: Claude <noreply@anthropic.com>

pylint/plugins/README.md

@@ -1042,3 +1042,13 @@ The light provides `color_mode` but no `supported_color_modes`. At runtime
 ("does not set supported color modes") from both `state_attributes` and
 `capability_attributes` whenever `supported_color_modes` is `None`. Set
 `_attr_supported_color_modes` or override the `supported_color_modes` property.
+
+
+## `home_assistant_enforce_config_flow_no_connection_class` checker
+
+Detects config flow classes that set `CONNECTION_CLASS`.
+
+### `W7438`: `home-assistant-config-flow-connection-class`
+
+`CONNECTION_CLASS` is no longer used by Home Assistant and should not be set
+on config flows. Remove the attribute.

pylint/plugins/pylint_home_assistant/checkers/config_flow/no_connection_class.py

@@ -0,0 +1,56 @@
+"""Checker for the removed CONNECTION_CLASS attribute in config flows."""
+
+from astroid import nodes
+from pylint.checkers import BaseChecker
+from pylint.lint import PyLinter
+
+from pylint_home_assistant.const import Module
+from pylint_home_assistant.helpers.module_info import parse_module
+
+_CONNECTION_CLASS = "CONNECTION_CLASS"
+
+
+class HassEnforceConfigFlowNoConnectionClassChecker(BaseChecker):
+    """Checker for CONNECTION_CLASS in config flows."""
+
+    name = "home_assistant_enforce_config_flow_no_connection_class"
+    priority = -1
+    msgs = {
+        "W7438": (
+            "Config flow should not set CONNECTION_CLASS",
+            "home-assistant-config-flow-connection-class",
+            "Used when a config flow class sets CONNECTION_CLASS. The attribute "
+            "is no longer used by Home Assistant and should not be set.",
+        ),
+    }
+    options = ()
+
+    def visit_assign(self, node: nodes.Assign) -> None:
+        """Check class-level assignments."""
+        if any(
+            isinstance(target, nodes.AssignName) and target.name == _CONNECTION_CLASS
+            for target in node.targets
+        ):
+            self._check(node)
+
+    def visit_annassign(self, node: nodes.AnnAssign) -> None:
+        """Check annotated class-level assignments."""
+        if (
+            isinstance(node.target, nodes.AssignName)
+            and node.target.name == _CONNECTION_CLASS
+        ):
+            self._check(node)
+
+    def _check(self, node: nodes.Assign | nodes.AnnAssign) -> None:
+        """Add a message if the assignment is in a config flow class body."""
+        parsed = parse_module(node.root().name)
+        if parsed is None or parsed.module != Module.CONFIG_FLOW:
+            return
+        if not isinstance(node.parent, nodes.ClassDef):
+            return
+        self.add_message("home-assistant-config-flow-connection-class", node=node)
+
+
+def register(linter: PyLinter) -> None:
+    """Register the checker."""
+    linter.register_checker(HassEnforceConfigFlowNoConnectionClassChecker(linter))

tests/pylint/config_flow/test_no_connection_class.py

@@ -0,0 +1,86 @@
+"""Tests for the config flow no CONNECTION_CLASS checker."""
+
+from __future__ import annotations
+
+import astroid
+from pylint.checkers import BaseChecker
+from pylint.testutils.unittest_linter import UnittestLinter
+import pytest
+
+from tests.pylint import assert_no_messages, walk_checker
+
+CONFIG_FLOW_MODULE = "homeassistant.components.test.config_flow"
+
+
+@pytest.mark.parametrize(
+    ("code", "module_name"),
+    [
+        pytest.param(
+            """
+        class TestFlow:
+            VERSION = 1
+        """,
+            CONFIG_FLOW_MODULE,
+            id="no_connection_class",
+        ),
+        pytest.param(
+            """
+        class TestFlow:
+            CONNECTION_CLASS = "local_polling"
+        """,
+            "homeassistant.components.test.sensor",
+            id="other_module",
+        ),
+        pytest.param(
+            """
+        CONNECTION_CLASS = "local_polling"
+        """,
+            CONFIG_FLOW_MODULE,
+            id="module_level",
+        ),
+    ],
+)
+def test_no_connection_class(
+    linter: UnittestLinter,
+    enforce_config_flow_no_connection_class_checker: BaseChecker,
+    code: str,
+    module_name: str,
+) -> None:
+    """Good test cases."""
+    root_node = astroid.parse(code, module_name)
+
+    with assert_no_messages(linter):
+        walk_checker(linter, enforce_config_flow_no_connection_class_checker, root_node)
+
+
+@pytest.mark.parametrize(
+    "code",
+    [
+        pytest.param(
+            """
+        class TestFlow:
+            CONNECTION_CLASS = "local_polling"
+        """,
+            id="assign",
+        ),
+        pytest.param(
+            """
+        class TestFlow:
+            CONNECTION_CLASS: str = "local_polling"
+        """,
+            id="annotated_assign",
+        ),
+    ],
+)
+def test_no_connection_class_bad(
+    linter: UnittestLinter,
+    enforce_config_flow_no_connection_class_checker: BaseChecker,
+    code: str,
+) -> None:
+    """Bad test cases."""
+    root_node = astroid.parse(code, CONFIG_FLOW_MODULE)
+
+    walk_checker(linter, enforce_config_flow_no_connection_class_checker, root_node)
+    messages = linter.release_messages()
+    assert len(messages) == 1
+    assert messages[0].msg_id == "home-assistant-config-flow-connection-class"

tests/pylint/conftest.py

@@ -3,6 +3,9 @@
 from pylint.checkers import BaseChecker
 from pylint.testutils.unittest_linter import UnittestLinter
 from pylint_home_assistant.checkers.class_module import HassEnforceClassModule
+from pylint_home_assistant.checkers.config_flow.no_connection_class import (
+    HassEnforceConfigFlowNoConnectionClassChecker,
+)
 from pylint_home_assistant.checkers.config_flow.no_name import (
     HassEnforceConfigFlowNoNameChecker,
 )
@@ -109,6 +112,17 @@ def enforce_serial_port_selector_usb_checker_fixture(
     return checker
 
 
+@pytest.fixture(name="enforce_config_flow_no_connection_class_checker")
+def enforce_config_flow_no_connection_class_checker_fixture(
+    linter: UnittestLinter,
+) -> BaseChecker:
+    """Fixture to provide a config_flow_no_connection_class checker."""
+    clear_caches()
+    checker = HassEnforceConfigFlowNoConnectionClassChecker(linter)
+    checker.module = "homeassistant.components.pylint_test"
+    return checker
+
+
 @pytest.fixture(name="enforce_config_flow_no_name_checker")
 def enforce_config_flow_no_name_checker_fixture(
     linter: UnittestLinter,