[image] Restructure into a platform component (#17416)

tests/unit_tests/test_config_normalization.py

@@ -1,6 +1,6 @@
 """Unit tests for esphome.config module."""
 
-from collections.abc import Generator
+from collections.abc import Callable, Generator
 import logging
 from pathlib import Path
 from unittest.mock import MagicMock, Mock, patch
@@ -8,7 +8,8 @@ from unittest.mock import MagicMock, Mock, patch
 import pytest
 
 from esphome import config, yaml_util
-from esphome.core import CORE
+from esphome.core import CORE, AutoLoad
+from esphome.types import ConfigType
 
 
 @pytest.fixture
@@ -116,6 +117,86 @@ def test_ota_with_platform_list_and_captive_portal(fixtures_dir: Path) -> None:
     assert "web_server" in platforms, f"Expected web_server platform in {platforms}"
 
 
+# ---------------------------------------------------------------------------
+# LEGACY_CONFIG_MIGRATE hook on LoadValidationStep -- the removable shim that
+# lets a platform component rewrite a pre-platform top-level config.
+# ---------------------------------------------------------------------------
+
+
+def _run_load_step(
+    domain: str,
+    conf: object,
+    migrate: Callable[[ConfigType], list | None] | None,
+) -> config.Config:
+    """Run a LoadValidationStep for a platform component with a given migrate hook."""
+    component = Mock()
+    component.is_platform_component = True
+    component.multi_conf_no_default = False
+    component.legacy_config_migrate = migrate
+
+    result = config.Config()
+    with (
+        patch("esphome.config.get_component", return_value=component),
+        patch("esphome.config._process_auto_load"),
+        patch("esphome.config._process_platform_config"),
+    ):
+        config.LoadValidationStep(domain, conf).run(result)
+    return result
+
+
+def test_legacy_migrate_rewrites_conf() -> None:
+    """A legacy config that the hook migrates is replaced with the new list."""
+    migrated = [{"platform": "file", "id": "a"}]
+    migrate = Mock(return_value=migrated)
+
+    result = _run_load_step("image", [{"id": "a", "file": "x.png"}], migrate)
+
+    migrate.assert_called_once_with([{"id": "a", "file": "x.png"}])
+    assert result["image"] == migrated
+
+
+def test_legacy_migrate_none_keeps_new_format() -> None:
+    """When the hook returns None the already-new config is left untouched."""
+    new_format = [{"platform": "file", "id": "a"}]
+    migrate = Mock(return_value=None)
+
+    result = _run_load_step("image", new_format, migrate)
+
+    migrate.assert_called_once_with(new_format)
+    assert result["image"] == new_format
+
+
+def test_legacy_migrate_absent_hook_is_noop() -> None:
+    """A platform component without the hook normalizes without migration."""
+    result = _run_load_step("image", {"id": "a"}, None)
+
+    # Bare dict still gets wrapped into a list by the normal normalization path.
+    assert result["image"] == [{"id": "a"}]
+
+
+def test_legacy_migrate_skipped_for_empty_conf() -> None:
+    """An empty config short-circuits before the hook is consulted."""
+    migrate = Mock(return_value=[{"platform": "file"}])
+
+    result = _run_load_step("image", [], migrate)
+
+    migrate.assert_not_called()
+    assert result["image"] == []
+
+
+def test_legacy_migrate_skipped_for_autoload() -> None:
+    """An auto-loaded (AutoLoad) config is never migrated."""
+    migrate = Mock(return_value=[{"platform": "file"}])
+    auto = AutoLoad()
+    auto["id"] = "a"
+
+    result = _run_load_step("image", auto, migrate)
+
+    migrate.assert_not_called()
+    # AutoLoad is dict-like, so normalization wraps it into a single-entry list.
+    assert result["image"] == [auto]
+
+
 def _write_merge_conflict_config(tmp_path: Path, *, suppress: bool) -> Path:
     """Create a config where two `<<` includes both define `logger:`.