Ditch dash.el

[Malabarba]

In Emacs 25.1, seq.el will be built-in (it's also a smaller package). So it would be nice to replace the dash dependency with seq.

There are currently 102 usages of dash functions that I could find by grepping for [(']-[-a-z]. About half of them -when-lets and -if-lets. The other half are functions provided by seq. The only exception I found was -map-indexed.

One way to replace the -when/if-lets is to drop 24.3 support and use when/if-let. Another is to copy the definition of when/if-let from subr-x.el. What do we think?

[bbatsov]

👍 Let's inline when-let and if-let and go forward with this.

I could try to help with this task. 

[bbatsov]

You're welcome to do so. :-)

[Malabarba]

👏👏👏👏🎉🎊🎆

:-)

I had a first look at the source. There seems to be a subx-r version that contains if-let, when-let. The subx-r version my Emacs 24.5 uses, does not. So inlining means copy them over ?

[bbatsov]

Yep.

Should I copy them to cider-common.el ?

[bbatsov]

No, copy them to cider-util.el.. You'll see we have other backported stuff there.

I think prefixing them with cider, like the other function in util, would be not a very good idea ?

[bbatsov]

Take this approach instead https://github.com/bbatsov/projectile/blob/master/projectile.el#L56

I don't want us to prefix them.

What about the other stuff from dash like -> ?

[bbatsov]

subr-x has thread-first and thread-last - you can copy and alias them (or use them with their Elisp names, it's all the same to me).