parent and dirrename should return In MonadThrow m

[harendra-kumar]

Should this be fixed?

>> isParentOf $(mkAbsDir "/") $(mkAbsDir "/")
False
>> parent $(mkAbsDir "/")
"/"
>> 

[chrisdone]

It's definitely an inconsistency.

[harendra-kumar]

There are two ways to fix that. Let parent throw an exception on / or let isParentOf return true in case of /. Unix traditionally allows cd .. when you are in root dir so the latter might be in line with that.

[chrisdone]

Indeed, the magicness of the root directory seems to give us no option but to pick something not great. isParentOf returning true for the same two arguments seems to mess with people's intuition of hierarchy.

Putting parent in MonadThrow m is inconvenient, but it is more correct. Perhaps we can plan a migration path.

[harendra-kumar]

The two options wrt root dir sound like this:

1. Sorry, its a dead end you can't go beyond this
2. You try to go up, you succeed and you find yourself in the same place

The first one is a more explicit and intuitive handling than the latter. Looks like a better option to me as well though a bit more inconvenient compared to the other one.

[chrisdone]

Indeed. I think (1) is explicit and the kind of thing this library is about.

[harendra-kumar]

Throw an exception or return a Maybe?

[mrkkrp]

I think it should throw just like all the other functions. It's more flexible and you can always get a Maybe value from MonadThrow m => ... m a.

[mrkkrp]

Should this be considered a duplicate of #18? Can we close it in favor of that issue?

[mrkkrp]

Closing in favor of #18. Should be resolved in version 0.6.0