Completer after another completer.

Hi, I wanted to use two completers one after another, but I'm not able to do that. FilesCompleter is my custom completer. After supplying the the file I want to trigger another completer BlockCompleter, but I don't know how to achieve that.

I tried following:

completer = NestedCompleter.from_nested_dict({
    'show': {
        'file': {
            FilesCompleter(): BlockCompleter()
        }
    },
})

But it gives me an error:

Exception 'FilesCompleter' object has no attribute 'lower'

Also another problem that I face is that for BlockCompleter to work I need result of FilesCompleter, but any of document methods or fields does not contain anything before the cursor position - eg. document.text is empty until i start typing.

What is the best way to achieve what I need?

Start with NestedCompleter.from_nested_dict and the Completer/document APIs mentioned in the report. Reproduce the sequence using FilesCompleter followed by BlockCompleter, then determine whether the supported result should be an implementation change or documented composition pattern; done means the first completer's result is available to the second.