[Python] Make option depend on previous option

Is there an idiomatic way, using the Python Click library, to create a command where one option depends on a value set by a previous option?

A concrete example (my use case) would be that a command takes an option of type click.File as input, but also an encoding option which specifies the encoding of the input stream:

import click

@click.command()
@click.option("--encoding", type=str, default="utf-8")
@click.option("--input",
type=click.File("r", encoding="CAN I SET THIS DYNAMICALLY BASED ON --encoding?"))
def cli(encoding, input):
pass


I guess it would have to involve some kind of deferred evaluation using a callable, but I'm not sure if it's even possible given the current Click API.

I've figured out I can do something along the following lines:

import click

@click.command()
@click.pass_context
@click.option("--encoding", type=str, default="utf-8")
@click.option("--input", type=str, default="-")
def cli(ctx, encoding, input):
input = click.File("r", encoding=encoding)(input, ctx=ctx)


But it somehow feels less readable / maintainable to decouple the option decorator from the semantically correct type constraint that applies to it, and put str in there instead as a dummy. So if there's a way to keep these two together, please enlighten me.

A proposed workaround:

I guess I could use the click.File type twice, making it lazy in the decorator so that the file isn't actually left opened, the first time around:

@click.option("--input", type=click.File("r", lazy=True), default="-")


This feels semantically more satisfying, but also redundant.

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