Allow configuration aliases

jsonargparse/actions.py

@@ -39,6 +39,19 @@
 class Action(LoggerProperty, ArgparseAction):
     """Base for jsonargparse Action classes."""
 
+    @property
+    def aliases(self):
+        return _action_aliases(self)
+
+
+def _action_aliases(self):
+    if not hasattr(self, '_aliases'):
+        options = {optstr.lstrip('-').replace('-', '_')
+                   for optstr in self.option_strings}
+        options = {opt for opt in options if len(opt) > 1}
+        self._aliases =  {self.dest} | options
+    return self._aliases
+
 
 def _is_branch_key(parser, key: str) -> bool:
     root_key = split_key_root(key)[0]
@@ -69,8 +82,11 @@ def _find_action_and_subcommand(
     if exclude is not None:
         actions = [a for a in actions if not isinstance(a, exclude)]
     fallback_action = None
+
     for action in actions:
-        if action.dest == dest:
+        # _StoreAction seems to break the property
+        # if dest in action.aliases:
+        if dest in _action_aliases(action):
             if isinstance(action, _ActionConfigLoad):
                 fallback_action = action
             else:

jsonargparse/core.py

@@ -1254,7 +1254,22 @@ def _apply_actions(
                 continue
 
             action_dest = action.dest if subcommand is None else subcommand+'.'+action.dest
-            value = cfg[action_dest]
+            try:
+                value = cfg[action_dest]
+            except KeyError:
+                from jsonargparse.actions import _action_aliases
+
+                # If the main key isn't in the config, check if it exists
+                # under an alias.
+                found = None
+                # for alias in get_alias_dest(action):
+                for alias in _action_aliases(action):
+                    if alias in cfg:
+                        value = cfg[alias]
+                        found = True
+                        break
+                if not found:
+                    raise
             if skip_fn and skip_fn(value):
                 continue
             with parser_context(parent_parser=self, lenient_check=True):

jsonargparse_tests/test_core.py

@@ -1223,5 +1223,26 @@ def test_add_multiple_config_arguments_error(self):
             parser.add_argument('--cfg2', action=ActionConfigFile)
 
 
+    def test_parser_alias(self):
+        # TODO:
+        # Successful parsing of a value in an alias saved as the dest key and the alias not appearing in the namespace.
+        # Failure to parse alias because the value does not agree with the argument type.
+        # Alias in a nested namespace.
+        # Alias with name that includes dashes -.
+
+        # Create a parser where --bar is an alias for --foo
+        parser = ArgumentParser()
+        parser.add_argument('--foo', '--bar')
+
+        parsed = parser.parse_string('foo: "aaa"')
+        assert parsed.foo == 'aaa'
+
+        parsed = parser.parse_string('bar: "bbb"')
+        assert parsed.foo == 'bbb'
+
+        parsed = parser.parse_args(['--bar', 'ccc'])
+        assert parsed.foo == 'ccc'
+
+
 if __name__ == '__main__':
     unittest.main(verbosity=2)