Update attribute font locking

Previously, attributes like `[<EntryPoint>]` would lock just fine, while
attributes like `[<Options("arg")>]` would fail to lock at all. This was because
the regex couldn't handle the parens and inner string, so would skip the whole
match.

This commit fixes that, making sure the parens lock in the same face as the rest
of the attribute, while any provided inner properties lock as a string.

Author: rectangular-zone

fsharp-mode-font.el

@@ -153,9 +153,8 @@ with initial value INITVALUE and optional DOCSTRING."
           "\\([A-Za-z_][A-Za-z0-9_']*\\)\\s-*:\\s-*\\([A-Za-z_][A-Za-z0-9_'<> \t]*\\)"))
 
 (def-fsharp-compiled-var fsharp-attributes-regexp
-  "\\[<[A-Za-z0-9_]+>\\]"
-  "Match attributes like [<EntryPoint>]")
-
+  "\\(\\[<[A-Za-z0-9_]+(?\\)\\(\".*\"\\)?\\()?>\\]\\)"
+  "Match attributes like [<EntryPoint>]; separately groups contained strings in attributes like [<Attribute(\"property\")>]")
 
 ;; F# makes extensive use of operators, many of which have some kind of
 ;; structural significance.
@@ -286,7 +285,10 @@ with initial value INITVALUE and optional DOCSTRING."
        (1 font-lock-comment-face)
        (2 font-lock-keyword-face))
       ;; attributes
-      (,fsharp-attributes-regexp . font-lock-preprocessor-face)
+      (,fsharp-attributes-regexp
+       (1 font-lock-preprocessor-face)
+       (2 font-lock-string-face)
+       (3 font-lock-preprocessor-face))
       ;; ;; type defines
       (,fsharp-type-def-regexp 1 font-lock-type-face)
       (,fsharp-function-def-regexp 1 font-lock-function-name-face)