[Fix #671] Font-lock properly multi-digit lambda args (#672)

Author: daveliepmann

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### Bugs fixed
+
+* [#671](https://github.com/clojure-emacs/clojure-mode/issues/671): Syntax highlighting for digits after the first in % args
+
 ## 5.18.1 (2023-11-24)
 
 ### Bugs fixed

clojure-mode.el

@@ -1058,7 +1058,7 @@ any number of matches of `clojure--sym-forbidden-rest-chars'."))
        1 'clojure-character-face)
       ;; lambda arguments - %, %&, %1, %2, etc
       ;; must come after character literals for \% to be handled properly
-      ("\\<%[&1-9]?" (0 font-lock-variable-name-face))
+      ("\\<%[&1-9]*" (0 font-lock-variable-name-face))
       ;; namespace definitions: (ns foo.bar)
       (,(concat "(\\<ns\\>[ \r\n\t]*"
                 ;; Possibly metadata, shorthand and/or longhand

test/clojure-mode-font-lock-test.el

@@ -901,13 +901,24 @@ DESCRIPTION is the description of the spec."
      (2 3 font-lock-keyword-face)
      ( 5 7 font-lock-function-name-face)))
 
-  (when-fontifying-it "should handle lambda-params"
+  (when-fontifying-it "should handle lambda-params %, %1, %n..."
     ("#(+ % %2 %3 %&)"
      (5 5 font-lock-variable-name-face)
      (7 8 font-lock-variable-name-face)
      (10 11 font-lock-variable-name-face)
      (13 14 font-lock-variable-name-face)))
 
+  (when-fontifying-it "should handle multi-digit lambda-params"
+    ;; % args with >1 digit are rare and unidiomatic but legal up to
+    ;; `MAX_POSITIONAL_ARITY` in Clojure's compiler, which as of today is 20
+    ("#(* %10 %15 %19 %20)"
+     ;; it would be better if this were just `font-lock-variable-name-face` but
+     ;; it seems to work as-is
+     (5 7   various-faces)
+     (9 11  font-lock-variable-name-face)
+     (13 15 font-lock-variable-name-face)
+     (17 19 various-faces)))
+
   (when-fontifying-it "should handle nils"
     ("(= nil x)"
      (4 6 font-lock-constant-face))