Ensure keyboard aliases do not point to themselves (#25500)

lib/python/qmk/cli/ci/validate_aliases.py

@@ -25,6 +25,21 @@ def _target_keyboard_exists(target):
     return True
 
 
+def _alias_not_self(alias):
+    """Check if alias points to itself, either directly or within a circular reference
+    """
+    aliases = keyboard_alias_definitions()
+
+    found = set()
+    while alias in aliases:
+        found.add(alias)
+        alias = aliases[alias].get('target', alias)
+        if alias in found:
+            return False
+
+    return True
+
+
 @cli.subcommand('Validates the list of keyboard aliases.', hidden=True)
 def ci_validate_aliases(cli):
     aliases = keyboard_alias_definitions()
@@ -32,7 +47,11 @@ def ci_validate_aliases(cli):
     success = True
     for alias in aliases.keys():
         target = aliases[alias].get('target', None)
-        if not _target_keyboard_exists(target):
+        if not _alias_not_self(alias):
+            cli.log.error(f'Keyboard alias {alias} should not point to itself')
+            success = False
+
+        elif not _target_keyboard_exists(target):
             cli.log.error(f'Keyboard alias {alias} has a target that doesn\'t exist: {target}')
             success = False