Remove voids from pollen/markup

Makes it consistent with the behavior of pollen/pre and pollen/markdown

pollen/private/main-base.rkt

@@ -9,7 +9,7 @@
 (define (make-parse-proc parser-mode root-proc)
   (cond
     [(eq? parser-mode default-mode-pagetree) decode-pagetree]
-    [(eq? parser-mode default-mode-markup) (λ (xs) (apply root-proc xs))] 
+    [(eq? parser-mode default-mode-markup) (λ (xs) (apply root-proc (remove-voids xs)))] 
     [(eq? parser-mode default-mode-markdown)
      (λ (xs) (let* ([xs (stringify xs)]
                     [xs ((dynamic-require 'markdown 'parse-markdown) xs)]

pollen/private/splice.rkt

@@ -53,3 +53,19 @@
   (check-equal? (strip-empty-attrs '(p ())) '(p))
   (check-equal? (strip-empty-attrs '(p () "foo")) '(p "foo"))
   (check-equal? (strip-empty-attrs '(p () (em () "foo") "bar")) '(p (em "foo") "bar")))
+
+
+;; used with pollen/markup to suppress void arguments,
+;; consistent with how pollen/pre and pollen/markdown handle them
+(define (remove-voids x)
+  (let loop ([x x])
+    (if (pair? x)
+        (for/list ([xi (in-list x)]
+                   #:unless (void? xi))
+                  (loop xi))
+        x)))
+
+(module+ test
+  (check-equal? (remove-voids (list 1 2 3 (void))) '(1 2 3))
+  (check-equal? (remove-voids (list 1 (void) 2 3 (list 4 5 6 (void)))) '(1 2 3 (4 5 6)))
+  (check-equal? (remove-voids (void)) (void)))

pollen/private/ts.rktd

@@ -1 +1 @@
-1511248782
+1511711794

pollen/test/test-langs.rkt

@@ -15,19 +15,22 @@
 
 
 (module test-pre pollen/pre
-  "hello world")
+  "hello world"
+  (void))
 (require (prefix-in pre: 'test-pre))
 (check-equal? pre:doc "hello world")
 
 
 (module test-markup pollen/markup
-  "hello world")
+  "hello world"
+  (void))
 (require (prefix-in markup: 'test-markup))
 (check-equal? markup:doc '(root "hello world"))
 
 
 (module test-markdown pollen/markdown
-  "hello world")
+  "hello world"
+  (void))
 (require (prefix-in markdown: 'test-markdown))
 (check-equal? markdown:doc '(root (p "hello world")))