resolve_command fails if cmd is None

On the documentation, an example is given for how to implement AliasedGroups

We have a command, which is intended to be run like this

axii workspace add

tab completion should then suggest the package names, which works. However, if there is a typo in the command, the command errors out with an ugly stack-trace if implemented according to the documentation.

axii workspaceTYPO add

~/git/axii$ axii workspaceTYPO add Traceback (most recent call last):
  File "/home/tobiasjacob/git/axii/axii", line 7, in <module>
    entry_point()
  File "/home/tobiasjacob/git/axii/.venv/lib/python3.10/site-packages/click/core.py", line 1134, in __call__
    return self.main(*args, **kwargs)
  File "/home/tobiasjacob/git/axii/.venv/lib/python3.10/site-packages/click/core.py", line 1054, in main
    self._main_shell_completion(extra, prog_name, complete_var)
  File "/home/tobiasjacob/git/axii/.venv/lib/python3.10/site-packages/click/core.py", line 1129, in _main_shell_completion
    rv = shell_complete(self, ctx_args, prog_name, complete_var, instruction)
  File "/home/tobiasjacob/git/axii/.venv/lib/python3.10/site-packages/click/shell_completion.py", line 49, in shell_complete
    echo(comp.complete())
  File "/home/tobiasjacob/git/axii/.venv/lib/python3.10/site-packages/click/shell_completion.py", line 291, in complete
    completions = self.get_completions(args, incomplete)
  File "/home/tobiasjacob/git/axii/.venv/lib/python3.10/site-packages/click/shell_completion.py", line 271, in get_completions
    ctx = _resolve_context(self.cli, self.ctx_args, self.prog_name, args)
  File "/home/tobiasjacob/git/axii/.venv/lib/python3.10/site-packages/click/shell_completion.py", line 498, in _resolve_context
    name, cmd, args = command.resolve_command(ctx, args)
  File "/home/tobiasjacob/git/axii/armarx_setup/cli/common.py", line 127, in resolve_command
    return cmd.name # if cmd else None, cmd, args
AttributeError: 'NoneType' object has no attribute 'name'

I suggest one of to changes:

• Simply removing the resolve_command function solves the issue. This is porably nicer, since the resolve_command function is nowhere else documented.

      def resolve_command(self, ctx, args):
          # always return the full command name
          _, cmd, args = super().resolve_command(ctx, args)
          return cmd.name, cmd, args
  

• Or changing the example to

      def resolve_command(self, ctx, args):
          # always return the full command name
          _, cmd, args = super().resolve_command(ctx, args)
          return cmd.name if cmd else None, cmd, args
  

solves the issue. Please not, that cmd.name if cmd else None is also implemented in src/click/core.py:1716

Start with the advanced command aliases example in the documentation and compare it with src/click/core.py:1716. Reproduce shell completion using an invalid command such as workspaceTYPO, then trace resolve_command in the reported example. Done means the typo no longer produces an AttributeError traceback, with the relevant documentation or behavior covered appropriately.