DJSON-57 Throw better exception on EOF in object or array reading

Author: puredanger

README.md

@@ -153,6 +153,7 @@ Change Log
 * Next
   * Fix [DJSON-50]: `read` can take a PushbackReader for repeated read use case
   * Fix `write` docstring to add `:indent` option added in [DJSON-18]
+  * Fix [DJSON-57]: Throw better exception when EOF encountered while reading array or object
   * Add [DJSON-46]: In `read`, add `:extra-data-fn` that can be provided to cause an eof check after value is read
   * Add [DJSON-54]: In `write`, add custom fallback fn for writing unknown types
   * Perf [DJSON-61]: Faster string writing when string is "simple"
@@ -246,6 +247,7 @@ Change Log
   * Source-compatible with clojure.contrib.json, except for the name change.
 
 [DJSON-61]: https://clojure.atlassian.net/browse/DJSON-61
+[DJSON-57]: https://clojure.atlassian.net/browse/DJSON-57
 [DJSON-54]: https://clojure.atlassian.net/browse/DJSON-54
 [DJSON-53]: https://clojure.atlassian.net/browse/DJSON-53
 [DJSON-52]: https://clojure.atlassian.net/browse/DJSON-52

src/main/clojure/clojure/data/json.clj

@@ -325,13 +325,17 @@
 (defn invalid-array-exception []
   (Exception. "JSON error (invalid array)"))
 
+(defn- eof-array-exception []
+  (EOFException. "JSON error (EOF in array)"))
+
 (defn- read-array* [^InternalPBR stream options]
   ;; Handles all array values after the first.
   (loop [result (transient [])]
     (let [r (conj! result (-read stream true nil options))]
       (codepoint-case (int (next-token stream))
         \] (persistent! r)
         \, (recur r)
+        -1 (throw (eof-array-exception))
         (throw (invalid-array-exception))))))
 
 (defn- read-array [^InternalPBR stream options]
@@ -342,19 +346,35 @@
     (codepoint-case c
       \] []
       \, (throw (invalid-array-exception))
+      -1 (throw (eof-array-exception))
       (do (.unreadChar stream c)
           (read-array* stream options)))))
 
+(defn- object-colon-exception []
+  (Exception. "JSON error (missing `:` in object)"))
+
+(defn- eof-object-exception []
+  (EOFException. "JSON error (EOF in object)"))
+
+(defn- invalid-key-exception [c]
+  (if (= c -1)
+    (throw (eof-object-exception))
+    (throw (Exception. (str "JSON error (non-string key in object), found `" (char c) "`, expected `\"`")))))
+
+(comment
+  (compile 'clojure.data.json)
+  )
+
 (defn- read-key [^InternalPBR stream]
   (let [c (int (next-token stream))]
     (if (= c (codepoint \"))
       (let [key (read-quoted-string stream)]
         (if (= (codepoint \:) (int (next-token stream)))
           key
-          (throw (Exception. "JSON error (missing `:` in object)"))))
+          (throw (object-colon-exception))))
       (if (= c (codepoint \}))
         nil
-        (throw (Exception. (str "JSON error (non-string key in object), found `" (char c) "`, expected `\"`")))))))
+        (invalid-key-exception c)))))
 
 (defn- read-object [^InternalPBR stream options]
   ;; Expects to be called with the head of the stream AFTER the
@@ -374,6 +394,7 @@
           (codepoint-case (int (next-token stream))
             \, (recur r)
             \} (persistent! r)
+            -1 (throw (eof-object-exception))
             (throw (Exception. "JSON error (missing entry in object)"))))
         (let [r (persistent! result)]
           (if (empty? r)

src/test/clojure/clojure/data/json_test.clj

@@ -407,6 +407,18 @@
   (is (thrown? java.io.EOFException
         (json/read-str "\"\\"))))
 
+(deftest throws-eof-in-arrays
+  (is (thrown? java.io.EOFException
+        (json/read-str "[1,")))
+  (is (thrown? java.io.EOFException
+        (json/read-str "[1,2,"))))
+
+(deftest throws-eof-in-objects
+  (is (thrown? java.io.EOFException
+        (json/read-str "{")))
+  (is (thrown? java.io.EOFException
+        (json/read-str "{\"\":1,"))))
+
 (deftest accept-eof
   (is (= ::eof (json/read-str "" :eof-error? false :eof-value ::eof))))