Added Kotlin lexer

[citizenmatt]

Based on Pygments parser, and version converted by @hastebrot.
Fixes #295

[hastebrot]

Any idea how I get the function generics highlighted as Punctuation, Name, Punctuation?

fun foo(arg: String) {
    println(arg)
}

fun <T> bar(arg: List<T>) {
    println(arg)
}

fun <S, T> baz(arg: Pair<S, T>) {
    println(arg)
}

[hastebrot]

Here is a lazy incomplete solution for a function state/rule:

rule %r'(fun)(\s+)' do
  groups Keyword, Text
  push :function
end

# ...

state :function do
  rule %r'(<)(.+)(>)(\s+)' do
    groups Operator, Name, Operator, Text
  end
  rule /#{id}/, Name::Function, :pop!
end

This needs to be improved in order to correctly highlight fun<S, T>foo(), fun <S, T> foo() and fun <S,\nT> foo().

[hastebrot]

Changes:

state :root do
  rule %r'(fun)' do token Keyword; push :function end
  # ...
end

state :function do
  rule /</, Punctuation, :function_type_params
  rule /\s+/, Text
  rule /#{id}(\.)/ do groups Name::Class, Operator end
  rule /#{id}/, Name::Function, :pop!
end

state :function_type_params do
  rule />/, Punctuation, :pop!
  mixin :root
end

Samples:

val foo: String = "foo"
val bar: List<String> = listOf("bar")
val baz: Pair<Int, String> = 42 to "baz"

fun foo(arg: String) {}
fun <T> bar(arg: List<T>) {}
fun <S, T> baz(arg: Pair<S, T>) {}

fun<T>Quux.foo() {}
fun <T : Any> Quux.bar() {}
inline fun <reified T : Any> Quux.baz() {}

[hastebrot]

"Kotlin" not "Java".

[dimsuz]

Hello! What needs to be done for this to be merged?
Kotlin is gaining popularity and it would be really nice to have syntax highlighting support for it.

[ElMassimo]

Yep, specially since Pygments has supported Kotlin for a while, and Rouge aims to be a drop-in replacement with Pygments.

Having language parity with Pygments is even more important since GitHub pages will only support Rouge starting May 1st.

[davidschreiber]

👍 Pushing for this PR as well. Would love too see Kotlin support in Rouge.

[hastebrot]

Here is list of remaining issues (tested with http://try.kotlinlang.org/#/Examples/Longer%20examples/Life/Life.kt):

• identifiers for class, interface, object, package, import, val, var, fun use the rule for Java identifiers.
• multi-line strings are not supported.
• 2..3 matches 2. as Number (CSS class m).
• matches non-keyword data as keyword.
• function generics are not supported (fun <T> foo() {}).

Update: This was also mentioned in the related issue: #295

[jneen]

Hi! As I'm sure you know, writing lexers takes a lot of time and work, and having language parity with Pygments is currently a rather unrealistic goal. But I do hope to merge the Kotlin lexer soon!

Since #476 includes this work, I'm closing this PR in favor of that one.