Allow XML for empty feeds (fixes #9)

Author: otherjoel

splitflap-lib/private/feed.rkt

@@ -141,7 +141,7 @@
        (raise-argument-error 'express-xml "valid URL (required for #<feed>)" feed-url))
      (match-define (feed feed-id site-url feed-name entries) f)
      (define entries-sorted (sort entries entry-newer?))
-     (define last-updated (feed-item-updated (car entries-sorted)))
+     (define last-updated (if (pair? entries-sorted) (feed-item-updated (car entries-sorted)) (infer-moment)))
      (define to-xml? (memq result-type '(xml xml-string)))
 
      (define feed-xpr
@@ -255,7 +255,7 @@
           `(itunes:category [[text ,cat1]]
                             (itunes:category [[text ,cat2]]))]
          [(? string? c) `(itunes:category [[text ,c]])]))
-     (define last-updated (episode-updated (car episodes-sorted)))
+     (define last-updated (if (pair? episodes-sorted) (episode-updated (car episodes-sorted)) (infer-moment)))
      (define to-xml? (memq result-type '(xml xml-string)))
 
      (define feed-xpr

splitflap-lib/tests.rkt

@@ -170,6 +170,10 @@ END
          "Kate Poster Posts"
          (list entry1 entry2 entry3-conflict))))
 
+;; Empty feeds should be allowed
+(check-not-exn (lambda () (express-xml (feed site-id "https://example.com" "Posts" '()) 'atom "https://example.com")))
+(check-not-exn (lambda () (express-xml (feed site-id "https://example.com" "Posts" '()) 'rss "https://example.com")))
+
 ;; Check podcast episode output
 (define test-ep1
   (parameterize ([current-timezone 0])
@@ -341,4 +345,18 @@ END
            (list "Leisure" "Animation & Manga")
            "https://example.com/cover-art.jpg"
            (person "Kate Poster" "kate@example.com")
-           #:explicit? #t)))
+           #:explicit? #t)))
+
+;; Empty podcast feeds should be allowed
+(check-not-exn
+ (lambda ()
+   (express-xml (podcast site-id
+                         "https://example.com"
+                         "Podcast"
+                         '()
+                         (list "Sports" "Swimming")
+                         "https://example.com/cover-art.jpg"
+                         (person "Kate Poster" "kate@example.com")
+                         #:explicit? #f)
+                'rss
+                "https://example.com")))