mypy raises errors when using `click.prompt()` due to `type` argument having incompatible type

[andrewlangemann]

I have a project that uses the latest version of mypy (0.910) and click (8.0.1). I am attempting to use click.prompt() and pass in the type argument but this is always causing mypy (with default settings) to find errors.

Here is an example:

import click
name = click.prompt('What is your name?', type=str)
age = click.prompt('What is your age?', type=int)

When I run mypy against this file, I get two errors:

main.py:2: error: Argument "type" to "prompt" has incompatible type "Type[str]"; expected "Optional[ParamType]"
main.py:3: error: Argument "type" to "prompt" has incompatible type "Type[int]"; expected "Optional[ParamType]"

To address these, I tried passing in some different values for type but to no avail (same issues all happen for int as well):

name = click.prompt('What is your name?', type=Optional[str])
# Returns error: Argument "type" to "prompt" has incompatible type "object"; expected "Optional[ParamType]"

name = click.prompt('What is your name?', type=StringParamType)
# Returns error: Argument "type" to "prompt" has incompatible type "Type[StringParamType]"; expected "Optional[ParamType]"

name = click.prompt('What is your name?', type=Optional[StringParamType])
# Returns error: Argument "type" to "prompt" has incompatible type "object"; expected "Optional[ParamType]"

Is this a bug or should I be providing something different to type?

Environment:

• Python version: 3.7.10
• Click version: 8.0.1
• mypy version: 0.910

[davidism]

It's half a bug with typing, and half a bug with your attempted workarounds.

The type of type should be type: Optional[Union[ParamType, Any]]. Happy to review a PR that fixes this.

The reason StringParamType didn't work for you is that's a class, not an instance of it. The singleton instance of StringParamType that you should use is click.STRING. Additionally, passing typing things like Optional[StringParamType] doesn't make sense, that's a type annotation not a parameter value.

[andrewlangemann]

Thank you @davidism - by using click.STRING and click.INT I have now appeased mypy :)

import click
name = click.prompt('What is your name?', type=click.STRING)
age = click.prompt('What is your age?', type=click.INT)