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

script/build_alias_registry.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+"""Generate esphome/component_aliases.py from component ALIASES declarations.
+
+Run without arguments to regenerate the registry; ``--check`` (run in CI)
+verifies it is up to date.
+"""
+
+import argparse
+from pathlib import Path
+import sys
+
+# The root directory of the repo
+root = Path(__file__).parent.parent
+# Make the repo's esphome package win over any installed copy
+sys.path.insert(0, str(root))
+
+from esphome.helpers import write_file_if_changed  # noqa: E402
+from esphome.loader import _build_alias_map  # noqa: E402
+
+parser = argparse.ArgumentParser()
+parser.add_argument(
+    "--check",
+    help="Check if the alias registry is up to date.",
+    action="store_true",
+)
+args = parser.parse_args()
+
+registry_file = root / "esphome" / "component_aliases.py"
+
+HEADER = '''"""Component alias registry.
+
+Generated by script/build_alias_registry.py - do not edit manually.
+See the component-alias section of esphome/loader.py.
+"""
+
+# alias -> (canonical component, removal version or None)
+COMPONENT_ALIASES: dict[str, tuple[str, str | None]] = {
+'''
+
+# _build_alias_map scans the real component tree and already rejects
+# duplicate and shadowing aliases with an EsphomeError.
+_, alias_meta = _build_alias_map()
+
+lines = [HEADER]
+for alias, meta in sorted(alias_meta.items()):
+    removal = f'"{meta.removal_version}"' if meta.removal_version else "None"
+    lines.append(f'    "{alias}": ("{meta.canonical}", {removal}),\n')
+lines.append("}\n")
+content = "".join(lines)
+
+if args.check:
+    if registry_file.read_text(encoding="utf-8") != content:
+        print("Component alias registry is not up to date.")
+        print("Please run `script/build_alias_registry.py`")
+        sys.exit(1)
+    print("Component alias registry is up to date")
+else:
+    write_file_if_changed(registry_file, content)
+    print(f"Wrote {registry_file}")