From 115ad9a41ce22811d0ed99c5fbca0e963fef634c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?D=C3=A1niel=20B=C3=A1tyai?= <dbatyai@inf.u-szeged.hu>
Date: Sun, 8 Sep 2019 23:49:27 +0200
Subject: [PATCH] Fix JSON.stringify for non-serializable properties (#3083)
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Fixes #3082.

JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai dbatyai@inf.u-szeged.hu
---
 .../ecma/builtin-objects/ecma-builtin-json.c  | 21 +++++----
 tests/jerry/regression-test-issue-3082.js     | 45 +++++++++++++++++++
 2 files changed, 57 insertions(+), 9 deletions(-)
 create mode 100644 tests/jerry/regression-test-issue-3082.js

diff --git a/jerry-core/ecma/builtin-objects/ecma-builtin-json.c b/jerry-core/ecma/builtin-objects/ecma-builtin-json.c
index b5e47b3d9..d84d68593 100644
--- a/jerry-core/ecma/builtin-objects/ecma-builtin-json.c
+++ b/jerry-core/ecma/builtin-objects/ecma-builtin-json.c
@@ -950,8 +950,8 @@ ecma_builtin_json_serialize_object (ecma_json_stringify_context_t *context_p, /*
       /* ecma_builtin_json_serialize_property already appended the result. */
       JERRY_ASSERT (ecma_is_value_empty (result));
 
-      last_prop = ecma_stringbuilder_get_size (&context_p->result_builder);
       ecma_stringbuilder_append_byte (&context_p->result_builder, LIT_CHAR_COMMA);
+      last_prop = ecma_stringbuilder_get_size (&context_p->result_builder);
     }
     else
     {
@@ -962,15 +962,18 @@ ecma_builtin_json_serialize_object (ecma_json_stringify_context_t *context_p, /*
     ecma_value_p = ecma_collection_iterator_next (ecma_value_p);
   }
 
-  /* Remove the last comma. */
-  ecma_stringbuilder_revert (&context_p->result_builder, last_prop);
-
-  if (last_prop != left_brace && has_gap)
+  if (last_prop != left_brace)
   {
-    /* We appended at least one element, and have a separator, so must append the stepback. */
-    ecma_stringbuilder_append_raw (&context_p->result_builder,
-                                   ecma_stringbuilder_get_data (&context_p->indent_builder),
-                                   stepback_size);
+    /* Remove the last comma. */
+    ecma_stringbuilder_revert (&context_p->result_builder, last_prop - 1);
+
+    if (has_gap)
+    {
+      /* We appended at least one element, and have a separator, so must append the stepback. */
+      ecma_stringbuilder_append_raw (&context_p->result_builder,
+                                     ecma_stringbuilder_get_data (&context_p->indent_builder),
+                                     stepback_size);
+    }
   }
 
   ecma_stringbuilder_append_byte (&context_p->result_builder, LIT_CHAR_RIGHT_BRACE);
diff --git a/tests/jerry/regression-test-issue-3082.js b/tests/jerry/regression-test-issue-3082.js
new file mode 100644
index 000000000..a339a0ae1
--- /dev/null
+++ b/tests/jerry/regression-test-issue-3082.js
@@ -0,0 +1,45 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+var obj = {
+  a: "str",
+  b: function() {},
+  c: true
+}
+
+assert (JSON.stringify (obj) === "{\"a\":\"str\",\"c\":true}");
+assert (JSON.stringify (obj, null, 2) === "{\n  \"a\": \"str\",\n  \"c\": true\n}");
+
+var obj = {
+  f: function() {}
+}
+
+assert (JSON.stringify (obj) === "{}");
+assert (JSON.stringify (obj, null, 2) === "{}");
+
+var obj = {
+  f: function() {},
+  a: null
+}
+
+assert (JSON.stringify (obj) === "{\"a\":null}");
+assert (JSON.stringify (obj, null, 2) === "{\n  \"a\": null\n}");
+
+var obj = {
+  a: false,
+  f: function() {}
+}
+
+assert (JSON.stringify (obj) === "{\"a\":false}");
+assert (JSON.stringify (obj, null, 2) === "{\n  \"a\": false\n}");