Basically, I'm trying to syntax highlight the following piece of coffeescript code the way I want it. Explanation of the syntax of coffeescript functions can be found here.
nameHere = (tstamp, moo, boo) ->
...
The names tstamp, moo and boo should be colored pink (and nothing else, not the commas and not the brackets) because they are parameters to a lambda function.
highOrderFun ((x) -> x * x) someList
Here it is the first x that is the parameter. Parameters can have default arguments:
class Foo
meth: (msg = "Hello", bar = "foo") ->
....
Default arguments can be variables themselves:
defColor = "red"
print = (msg, color = defColor) ->
...
So msg
and color
above should be highlighted, but not defColor
. An even trickier case is functions with default arguments that themselves are functions. I think that is to hard for emacs' font-lock to highlight correctly, but I'm including it anyway:
funTakingFuns = (f1 = ((a, b) -> a*b), f2 = ((c, d) -> c/d)) ->
...
This appears to be pretty complicated to achieve in emacs because you want the highlighting to be context sensitive. I've read up on the documentation on font-lock but haven't been able to figure it out.
I'd be grateful if someone could show me what to set font-lock-defaults
to make it syntax highlight the way I want it.
Update Showing more coffeescript syntax examples.
font-lock-keywords
allows function values in the MATCHER
field:
where
MATCHER
can be either the regexp to search for, or the function name to call to make the search (called with one argument, the limit of the search; it should return non-nil
, move point, and setmatch-data
appropriately if it succeeds; likere-search-forward
would).
So we need to write a function that would search for the next function argument in the buffer.
Something like this:
(defun coffee-match-next-argument (limit)
(let ((start (point)))
;; Look for the arrow.
(when (re-search-forward ") *->" limit t)
;; Save the position of the closing paren.
(let ((stop (point)))
(goto-char (match-beginning 0))
;; Go to the opening paren.
(goto-char (nth 1 (syntax-ppss)))
;; If we're before our initial position, go forward.
;; We don't want to find the same symbols again.
(when (> start (point))
(goto-char start))
;; Look for the next symbol until the arrow.
(or (re-search-forward "\\((\\|,\\) *\\(\\(\\sw\\|_\\)+\\)" stop 'mv)
(coffee-match-next-argument limit))))))
And the setup, to use with existing coffee-mode
:
(font-lock-add-keywords
'coffee-mode
'((coffee-match-next-argument 2 font-lock-variable-name-face)))
You can also use this in font-lock-defaults
, of course.
This will likely use some other color than pink, but that's easy to change.