[core] Load component aliases from a generated registry (#18335)

esphome/loader.py

@@ -269,10 +269,9 @@ def _lookup_module(domain: str, exception: bool) -> ComponentManifest | None:
     # If `domain` is the legacy name of a renamed component, redirect to the
     # canonical module so the rest of the loader (and every caller of
     # `get_component(legacy)`) transparently sees the new component.
-    alias_map = _get_alias_map()
-    if domain in alias_map:
-        canonical = alias_map[domain]
-        manif = _lookup_module(canonical, exception)
+    alias_meta = get_alias_metadata().get(domain)
+    if alias_meta is not None:
+        manif = _lookup_module(alias_meta.canonical, exception)
         if manif is not None:
             _COMPONENT_CACHE[domain] = manif
         return manif
@@ -329,8 +328,10 @@ def _replace_component_manifest(domain: str, manifest: ComponentManifest) -> Non
 # ---------------------------------------------------------------------------
 #
 # A component can declare ``ALIASES = ["legacy_name"]`` (and optionally
-# ``ALIAS_REMOVAL_VERSION = "YYYY.M.0"``) in its ``__init__.py``. Two
-# integrations are then wired up automatically:
+# ``ALIAS_REMOVAL_VERSION = "YYYY.M.0"``) in its ``__init__.py``, then run
+# ``script/build_alias_registry.py`` to regenerate
+# ``esphome/component_aliases.py`` (CI and a unit test fail if the registry
+# is stale). Two integrations are then wired up automatically:
 #
 #   1. **Python imports** — a ``sys.meta_path`` finder (``_AliasFinder``)
 #      intercepts ``esphome.components.<legacy>``/``...<legacy>.<sub>``
@@ -344,13 +345,13 @@ def _replace_component_manifest(domain: str, manifest: ComponentManifest) -> Non
 #      dependency checks, schema validation and codegen all see only the
 #      canonical name.
 #
-# Both lookups are populated by ``_build_alias_map``, which **AST-parses**
-# every component's ``__init__.py`` rather than importing it. That keeps the
-# cost low: scanning ~400 components on disk takes ~5 ms instead of the
-# multi-second cost of executing every component's import side-effects.
+# Both lookups read the checked-in registry in ``esphome.component_aliases``
+# (generated by ``script/build_alias_registry.py``, verified in CI), so no
+# component-directory scan happens at runtime. ``_build_alias_map`` below is
+# the generator's scan implementation; it **AST-parses** each component's
+# ``__init__.py`` rather than importing it.
 
 
-_ALIAS_MAP_CACHE: dict[str, str] | None = None
 _ALIAS_META_CACHE: dict[str, "AliasMeta"] | None = None
 
 
@@ -367,31 +368,17 @@ class AliasMeta:
     removal_version: str | None
 
 
-def _ensure_alias_caches() -> None:
-    """Populate both alias caches from a single directory scan.
-
-    ``_build_alias_map`` returns both maps together, so building them in one
-    shot avoids scanning every component's ``__init__.py`` twice when a run
-    needs both the canonical map (loader) and the metadata map (config
-    pre-pass).
-    """
-    global _ALIAS_MAP_CACHE, _ALIAS_META_CACHE
-    if _ALIAS_MAP_CACHE is None or _ALIAS_META_CACHE is None:
-        _ALIAS_MAP_CACHE, _ALIAS_META_CACHE = _build_alias_map()
-
-
-def _get_alias_map() -> dict[str, str]:
-    """Return the legacy-name → canonical-name map, building it lazily."""
-    _ensure_alias_caches()
-    return _ALIAS_MAP_CACHE
-
-
 def get_alias_metadata() -> dict[str, AliasMeta]:
-    """Return the legacy-name → :class:`AliasMeta` map (cached).
+    """Return the legacy-name → :class:`AliasMeta` map, built lazily from
+    the generated registry."""
+    global _ALIAS_META_CACHE  # noqa: PLW0603
+    if _ALIAS_META_CACHE is None:
+        from esphome.component_aliases import COMPONENT_ALIASES
 
-    Used by the YAML pre-pass to format a per-alias deprecation warning.
-    """
-    _ensure_alias_caches()
+        _ALIAS_META_CACHE = {
+            alias: AliasMeta(canonical=canonical, removal_version=removal_version)
+            for alias, (canonical, removal_version) in COMPONENT_ALIASES.items()
+        }
     return _ALIAS_META_CACHE
 
 
@@ -537,11 +524,11 @@ class _AliasFinder(importlib.abc.MetaPathFinder):
         # least three parts, so ``parts[2]`` (the domain) always exists.
         parts = fullname.split(".")
         domain = parts[2]
-        alias_map = _get_alias_map()
-        if domain not in alias_map:
+        alias_meta = get_alias_metadata().get(domain)
+        if alias_meta is None:
             return None
 
-        parts[2] = alias_map[domain]
+        parts[2] = alias_meta.canonical
         canonical_fullname = ".".join(parts)
         try:
             canonical_module = importlib.import_module(canonical_fullname)