Re: Should mode commands be idempotent?

[Clément Pit-Claudel]

On 2017-09-20 00:29, Stefan Monnier wrote:
>> Is there a way inside of a minor mode to check if it was already
>> enabled before the current call, short of having a second variable
>> for that?
>
> It shouldn't be needed: the idempotence should emerge naturally from the
> way the code is written, rather than being the result of special tests
> to detect that particular situation.

I'm not too sure: take the example of visual-line-mode: how do you make that 
idempotent without explicitly checking whether the mode has already been 
activated?