[processor] improved error message for non-array EOF

processor.go

@@ -165,6 +165,9 @@ func (p processor) handleNonArray(j *json.JSON, clue byte) error {
 
 	n, err := j.WriteCurrentTo(out, true)
 	if err != nil {
+		if err == io.EOF {
+			return errNonArrayEOF(guessJSONType(clue))
+		}
 		return err
 	}
 	if n > 0 {
@@ -209,6 +212,13 @@ func errNotArrayWas(t string) error {
 	return fmt.Errorf("expected structure to be an array but found: %s", t)
 }
 
+func errNonArrayEOF(t string) error {
+	if t == "" {
+		return fmt.Errorf("JSON data ended prematurely")
+	}
+	return fmt.Errorf("file ended before the end of value (%s)", t)
+}
+
 func errBadPath(chunk string) error {
 	return fmt.Errorf("path node did not exist: %s", chunk)
 }

processor_test.go

@@ -255,6 +255,13 @@ func TestProcessor(t *testing.T) {
 			expErr: errArrayEOF(3),
 		},
 
+		{
+			name:   "array that doesn't end (trailing ws)",
+			in:     sreader("[1, 2, 3,  "),
+			exp:    "1\n2\n3\n",
+			expErr: errArrayEOF(3),
+		},
+
 		{
 			name:   "array that doesn't end - stutter comma",
 			in:     sreader("[1, 2, 3,,"),
@@ -295,7 +302,7 @@ func TestProcessor(t *testing.T) {
 			name:   "object that doesn't close",
 			in:     sreader(`{"x":`),
 			exp:    `{"x":`,
-			expErr: io.EOF,
+			expErr: errNonArrayEOF("object"),
 		},
 		// FUTURE: perhaps error
 		{