@meeseeksdev tag tab-completion

I have a use case where I would love to be able to do this - a tree-like xarray data structure which can be indexed with file-like paths, e.g. 'path/to/node', or even 'path/to/../to/node'.

For path segments like . and .. to work I would need to be able to dynamically alter the list of possible path completions based on the partial path already typed out. So this suggestion

Something like: my_object['str <tab>
causes _ipython_key_completions_(prefix: str) to be triggered, where prefix == 'str'

would work for me.

Looking inside the ipython completer, it seems there is already a key_prefix that gets read from the prompt.

This is available internally before _get_keys(obj) is performed, which is where _ipython_key_completions_() is called.

Could we simply pass key_prefix as an optional argument down through _get_keys and into _ipython_key_completions_()? Then if the user's class gets a chance to say what the list of possible keys should be given the currently-typed-out prefix?