From 0c2ada98ff7a6f73bb763c418d4919d473814bea Mon Sep 17 00:00:00 2001
From: Ben Greenman <benjaminlgreenman@gmail.com>
Date: Sat, 8 Dec 2018 16:31:58 -0500
Subject: [PATCH] json: improve 'bad input' error message (#2420)

When 'read-json' finds "bad input", print the input to try to show what
went wrong.
---
 racket/collects/json/main.rkt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/racket/collects/json/main.rkt b/racket/collects/json/main.rkt
index 24db155812..82cf23cdd6 100644
--- a/racket/collects/json/main.rkt
+++ b/racket/collects/json/main.rkt
@@ -248,7 +248,7 @@
               (cond [(equal? m #"\"") (read-string)]
                     [(equal? m #"[")  (read-list 'array #rx#"^\\]" read-json)]
                     [(equal? m #"{")  (read-hash)])))]
-      [else (err "bad input")]))
+      [else (err (format "bad input~n ~e" (peek-bytes (sub1 (error-print-width)) 0 i)))]))
   ;;
   (read-json #t))