Click option completion callback doesn't have access to context.params for parsed values of already typed arguments.

Click option completion callback doesn't have access to context.params for parsed values of already typed arguments during shell completion:

import click

def test_completer(ctx, param, incomplete):
    import sys
    print(f"1: {param= }", file=sys.stderr)
    print(f"2: {incomplete= }", file=sys.stderr)
    print(f"3: {ctx.params = }", file=sys.stderr)
    return []

@click.command()
@click.argument('type', shell_complete=test_completer)
@click.option('--test', shell_complete=test_completer)
def app(type, count):
    pass

Output:

app foo --test [TAB] [TAB]
1: param= <Option test>
2: incomplete= ''
3: ctx.params = {'type': None, 'test': None}

Thus the context inside option callback does not have access to already typed argument.

But vice versa works:

app --test bar [TAB] [TAB] 
1: param= <Argument type>
2: incomplete= ''
3: ctx.params = {'test': 'bar', 'type': None}

The context inside argument callback have access to already typed option.

I think it should be the same in both cases.

Environment:

• Python version: 3.8
• Click version: 8.0.3

Start by running the reproduction in the issue with Click's shell completion callbacks and compare the context passed to the option and argument completers. Done means an option completer can access already typed argument values just as the argument completer accesses typed option values, with a regression test covering both orders.