return resolved name, not original name

CHANGES.rst

@@ -20,6 +20,11 @@ Unreleased
     regular options do from ``default``. :issue:`1886`
 -   Added documentation that custom parameter types may be passed
     already valid values in addition to strings. :issue:`1898`
+-   Resolving commands returns the name that was given, not
+    ``command.name``, fixing an unintended change to help text and
+    ``default_map`` lookups. When using patterns like ``AliasedGroup``,
+    override ``resolve_command`` to change the name that is returned if
+    needed. :issue:`1895`
 
 
 Version 8.0.0

docs/advanced.rst

@@ -35,7 +35,6 @@ it would accept ``pus`` as an alias (so long as it was unique):
 .. click:example::
 
     class AliasedGroup(click.Group):
-
         def get_command(self, ctx, cmd_name):
             rv = click.Group.get_command(self, ctx, cmd_name)
             if rv is not None:
@@ -48,6 +47,11 @@ it would accept ``pus`` as an alias (so long as it was unique):
                 return click.Group.get_command(self, ctx, matches[0])
             ctx.fail(f"Too many matches: {', '.join(sorted(matches))}")
 
+        def resolve_command(self, ctx, args):
+            # always return the full command name
+            _, cmd, args = super().resolve_command(ctx, args)
+            return cmd.name, cmd, args
+
 And it can then be used like this:
 
 .. click:example::

examples/aliases/aliases.py

@@ -67,6 +67,11 @@ def get_command(self, ctx, cmd_name):
             return click.Group.get_command(self, ctx, matches[0])
         ctx.fail(f"Too many matches: {', '.join(sorted(matches))}")
 
+    def resolve_command(self, ctx, args):
+        # always return the command's name, not the alias
+        _, cmd, args = super().resolve_command(ctx, args)
+        return cmd.name, cmd, args
+
 
 def read_config(ctx, param, value):
     """Callback that is used whenever --config is passed.  We use this to

src/click/core.py

@@ -1717,7 +1717,7 @@ def resolve_command(
             if split_opt(cmd_name)[0]:
                 self.parse_args(ctx, ctx.args)
             ctx.fail(_("No such command {name!r}.").format(name=original_cmd_name))
-        return cmd.name if cmd else None, cmd, args[1:]
+        return cmd_name if cmd else None, cmd, args[1:]
 
     def get_command(self, ctx: Context, cmd_name: str) -> t.Optional[Command]:
         """Given a context and a command name, this returns a

tests/test_commands.py

@@ -285,6 +285,10 @@ class AliasedGroup(click.Group):
         def get_command(self, ctx, cmd_name):
             return push
 
+        def resolve_command(self, ctx, args):
+            _, command, args = super().resolve_command(ctx, args)
+            return command.name, command, args
+
     cli = AliasedGroup()
 
     @cli.command()
@@ -296,6 +300,16 @@ def push():
     assert result.output.startswith("Usage: root push [OPTIONS]")
 
 
+def test_group_add_command_name(runner):
+    cli = click.Group("cli")
+    cmd = click.Command("a", params=[click.Option(["-x"], required=True)])
+    cli.add_command(cmd, "b")
+    # Check that the command is accessed through the registered name,
+    # not the original name.
+    result = runner.invoke(cli, ["b"], default_map={"b": {"x": 3}})
+    assert result.exit_code == 0
+
+
 def test_unprocessed_options(runner):
     @click.command(context_settings=dict(ignore_unknown_options=True))
     @click.argument("args", nargs=-1, type=click.UNPROCESSED)