Updating read-json to produce eof when appropriate.

collects/json/json.scrbl

@@ -79,9 +79,10 @@ the @rfc for more information about JSON.
 
 @defproc[(read-json [in input-port? (current-input-port)]
                     [#:null jsnull any? (json-null)])
-         jsexpr?]{
+         (or/c jsexpr? eof-object?)]{
   Reads a @tech{jsexpr} from a JSON-encoded input port @racket[in] as a
-  Racket (immutable) value.}
+  Racket (immutable) value, or produces @racket[eof] if only whitespace
+  remains.}
 
 @defproc[(string->jsexpr [str string?] [#:null jsnull any? (json-null)])
          jsexpr?]{

collects/json/main.rkt

@@ -156,7 +156,7 @@
       (list (string->symbol k) (read-json)))
     (apply hasheq (apply append (read-list 'object #rx#"^}" read-pair))))
   ;;
-  (define (read-json)
+  (define (read-json #:eof-ok? [eof-ok? #false])
     (skip-whitespace)
     (cond
       [(regexp-try-match #px#"^true\\b"  i) #t]
@@ -171,9 +171,10 @@
               (cond [(equal? m #"\"") (read-string)]
                     [(equal? m #"[")  (read-list 'array #rx#"^\\]" read-json)]
                     [(equal? m #"{")  (read-hash)])))]
+      [(and eof-ok? (regexp-try-match #px#"$" i)) eof]
       [else (err "bad input")]))
   ;;
-  (read-json))
+  (read-json #:eof-ok? #true))
 
 ;; ----------------------------------------------------------------------------
 ;; Convenience functions

collects/json/tests/json.rkt

@@ -95,6 +95,13 @@
         (string->jsexpr @T{ " \b\n\r\f\t\\\"\/ " }) => " \b\n\r\f\t\\\"/ "
         (string->jsexpr @T{ "\uD834\uDD1E" }) => "\U1D11E"
         (string->jsexpr @T{ "\ud834\udd1e" }) => "\U1d11e"
+        ;; EOF detection
+        (for/list ([je (in-port read-json
+                                (open-input-string
+                                  @T{ 1 [2,3] "four" }))])
+          je)
+        =>
+        '(1 (2 3) "four")
         ))
 
 (test do (pred-tests)