expand input contract for `->html`

scribblings/template.scrbl

@@ -15,12 +15,12 @@ This module also provides everything from @racketmodname[sugar/coerce].
 
 @defproc[
 (->html
-[xexpr xexpr?]
+[xexpr-or-xexprs (or/c xexpr? (listof xexpr?))]
 [#:tag html-tag (or/c #f txexpr-tag?) #f]
 [#:attrs html-attrs (or/c #f txexpr-attrs?) #f]
 [#:splice splice-html? boolean? #f])
 string?]
-Convert @racket[_xexpr] to an HTML string. Similar to @racket[xexpr->string], but consistent with the HTML spec, text that appears within @code{script} or @code{style} blocks will not be escaped.
+Convert @racket[_xexpr-or-xexprs] to an HTML string. Similar to @racket[xexpr->string], but consistent with the HTML spec, text that appears within @code{script} or @code{style} blocks will not be escaped.
 
 @examples[#:eval my-eval
 (define tx '(root (script "3 > 2") "Why is 3 > 2?"))
@@ -28,7 +28,7 @@ Convert @racket[_xexpr] to an HTML string. Similar to @racket[xexpr->string], bu
 (->html tx)
 ]
 
-The optional keyword arguments @racket[_html-tag] and @racket[_html-attrs] let you set the outer tag and attributes for the generated HTML. If @racket[_xexpr] already has an outer tag or attributes, they will be replaced.
+The optional keyword arguments @racket[_html-tag] and @racket[_html-attrs] let you set the outer tag and attributes for the generated HTML. If @racket[_xexpr-or-xexprs] already has an outer tag or attributes, they will be replaced.
 
 @examples[#:eval my-eval
 (define tx '(root ((id "huff")) "Bunk beds"))
@@ -38,7 +38,7 @@ The optional keyword arguments @racket[_html-tag] and @racket[_html-attrs] let y
 (->html tx #:tag 'div #:attrs '((id "doback")))
 ]
 
-Whereas if @racket[_xexpr] has no tag or attributes, they will be added. If you supply attributes without a tag, you'll get an error.
+Whereas if @racket[_xexpr-or-xexprs] has no tag or attributes, they will be added. If you supply attributes without a tag, you'll get an error.
 
 @examples[#:eval my-eval
 (define x "Drum kit")
@@ -68,11 +68,22 @@ If the generated HTML has an outer tag, the @racket[_splice-html?] option will s
 Be careful not to pass existing HTML strings into this function, because the angle brackets will be escaped. Fine if that's what you want, but you probably don't.
 
 @examples[#:eval my-eval
-(define tx '(p "You did" (em "what?")))
+(define tx '(p "You did " (em "what?")))
 (->html tx)
 (->html (->html tx))
 ]
 
+As the input contract suggests, this function can take either a single @racket[xexpr?] or a list of @racket[xexpr?], with the expected results.
+
+@examples[#:eval my-eval
+(define tx '(p "You did " (em "what?")))
+(->html tx)
+(define txs '("You " "did " (em "what?")))
+(->html txs)
+(->html #:tag 'p txs)
+]
+
+
 @deftogether[(
 
 @defproc[

template.rkt

@@ -105,11 +105,18 @@
   (define paren-match (cadr matches))
   paren-match)
 
-(define+provide/contract (->html x #:tag [tag #f] #:attrs [attrs #f] #:splice [splice? #f])
-  ((xexpr?) (#:tag (or/c #f txexpr-tag?) #:attrs (or/c #f txexpr-attrs?) #:splice boolean?) . ->* . string?)
+(define placeholder-tag (gensym))
+
+(define+provide/contract (->html x-in #:tag [tag #f] #:attrs [attrs #f] #:splice [splice? #f])
+  (((or/c xexpr? (listof xexpr?))) (#:tag (or/c #f txexpr-tag?) #:attrs (or/c #f txexpr-attrs?) #:splice boolean?) . ->* . string?)
+
+  (define x (cond
+              [(txexpr? x-in) x-in]
+              [(list? x-in) (cons 'html x-in)]
+              [else x-in]))
   
   (when (and (not (txexpr? x)) attrs (not tag))
-    (error '->html "can't use attribute list '~a without a #:tag argument" attrs))
+    (raise-argument-error '->html (format "can't use attribute list ~v without a #:tag argument" attrs)))
   
   (if (or tag (txexpr? x))
       (let ()
@@ -117,7 +124,7 @@
         (define html-attrs (or attrs (and (txexpr? x) (get-attrs x)) null))
         (define html-elements (or (and (txexpr? x) (get-elements x)) (list x)))
         (define html (xexpr->html (make-txexpr html-tag html-attrs html-elements)))
-        (if splice?
+        (if (or splice? (and (list? x-in) (not (txexpr? x-in)) (not tag)))
             (trim-outer-tag html)
             html))
       (xexpr->html x)))
@@ -136,7 +143,12 @@
  (check-exn exn:fail? (λ() (->html #:attrs '((id "dale")) x) "hello")) ;; won't work without tag
  (check-equal? (->html #:splice #t x) "hello")
  (check-equal? (->html #:tag 'brennan #:attrs '((id "dale")) x) "<brennan id=\"dale\">hello</brennan>")
- (check-equal? (->html #:tag 'brennan #:attrs '((id "dale")) #:splice #t x) "hello"))
+ (check-equal? (->html #:tag 'brennan #:attrs '((id "dale")) #:splice #t x) "hello")
+
+ (define xs '("hello " (em "you") " " 42))
+ (check-equal? (->html xs) "hello <em>you</em> &#42;")
+ (check-equal? (->html #:splice #t xs) "hello <em>you</em> &#42;")
+ (check-equal? (->html #:tag 'div xs) "<div>hello <em>you</em> &#42;</div>"))
 
 (provide when/block)
 (define-syntax (when/block stx)