feat: Style.Transform for altering strings at render time

[meowgorithm]

So with this you can basically:

s := NewStyle().Transform(strings.ToUpper)
fmt.Println(s.Render("raow!") // "RAOW!"

Some things to consider:

• Should it accept multiple functions?
• Is Transform the best name for this?
• Should it ignore ANSI sequences?

Closes #229.

[maaslalani]

Looks great to me, this will make things much more flexible!

[maaslalani]

1. I personally like the Transform naming.
2. I think we don't have to take multiple transform functions since they are stackable i.e.:

s := NewStyle().Transform(func(s string) string {
  return strings.ToUpper(removeUnderline(prefix(strings.TrimSpace(s))))
})

but it could be nicer to have the following API:

s := NewStyle().Transform(strings.TrimSpace, prefix, removeUnderline, strings.ToUpper)

We can always merge this in to get and then do the multiple function later as that would not be / cause a breaking change to the API.

[maaslalani]

Should we have an UnsetTransform for consistency?

[meowgorithm]

100% — thanks for catching this!

[maaslalani]

Added 9d6896c

[meowgorithm]

I think we don't have to take multiple transform functions since they are stackable i.e.:

s := NewStyle().Transform(func(s string) string {
  return strings.ToUpper(removeUnderline(prefix(strings.TrimSpace(s))))
})

but it could be nicer to have the following API:

s := NewStyle().Transform(strings.TrimSpace, prefix, removeUnderline, strings.ToUpper)

We can always merge this in to get and then do the multiple function later as that would not be / cause a breaking change to the API.

Agreed; we can feel it out and add it if we feel we need it. Thanks, @maaslalani.

[bashbunni]

Happy to play around with this before merging to provide some feedback in how it feels to work with in Glamour. Funny, Muesli and I were just talking about these features being missing from Lip Gloss for Glamour. I'm not quite there yet, so if you're in a rush to merge, then I can provide feedback at a later time. Otherwise happy to try it out over the next few weeks using this branch.

[meowgorithm]

That would be awesome, Bash. No hurry to merge over here. This actually came out of some discussions with Muesli during table development so it totally makes sense that this plays into new Glamour (should we call it Glamour Total Makeover or something?).

[bashbunni]

✨ Glossy Glamour ✨
ok perfect, will do

[maaslalani]

Should we merge this? It will be quite useful for list enumerations where we pass an enumerator (i.e IV) and pass a EnumeratorStyle (NewStyle().Transform(func(s string) string { return "(" + s ")" }) to allow many different configurations for the styling of the enumerator:

For example:

IV
IV.
(II)
iv
iv.
(iv)

A
A.
(A)
a
a.
(a)

[meowgorithm]

Just a note here for posterity's sake: this was merged so it can be used in the forthcoming list sub-package.