JSON.parse errors made user-friendly

Part of the improve error messages initiative.

Based on a resource of JSON.parse() errors found at
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/JSON_bad_parse

Previously JSON.parse(NaN) would output:
SyntaxError: Unexpected token N in JSON at position 0
Now the output is:
SyntaxError: "NaN" is not valid JSON

Previously JSON.parse("{a:1}") would output:
SyntaxError: Unexpected token a in JSON at position 1
Now the output is:
SyntaxError: Expected property name or '}' in JSON at position 1

Bug: v8:6551
Change-Id: Ic9fad1fdbd295e1302805b81e6603fc526121960
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3513684Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Issack John <issackjohn@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#80567}

src/common/message-template.h

@@ -481,9 +481,40 @@ namespace internal {
   T(InvalidUnusedPrivateStaticMethodAccessedByDebugger,                        \
     "Unused static private method '%' cannot be accessed at debug time")       \
   T(JsonParseUnexpectedEOS, "Unexpected end of JSON input")                    \
-  T(JsonParseUnexpectedToken, "Unexpected token % in JSON at position %")      \
   T(JsonParseUnexpectedTokenNumber, "Unexpected number in JSON at position %") \
   T(JsonParseUnexpectedTokenString, "Unexpected string in JSON at position %") \
+  T(JsonParseUnterminatedString, "Unterminated string in JSON at position %")  \
+  T(JsonParseExpectedPropNameOrRBrace,                                         \
+    "Expected property name or '}' in JSON at position %")                     \
+  T(JsonParseExpectedCommaOrRBrack,                                            \
+    "Expected ',' or ']' after array element in JSON at position %")           \
+  T(JsonParseExpectedCommaOrRBrace,                                            \
+    "Expected ',' or '}' after property value in JSON at position "            \
+    "%")                                                                       \
+  T(JsonParseExpectedDoubleQuotedPropertyName,                                 \
+    "Expected double-quoted property name in JSON at position %")              \
+  T(JsonParseExponentPartMissingNumber,                                        \
+    "Exponent part is missing a number in JSON at position %")                 \
+  T(JsonParseExpectedColonAfterPropertyName,                                   \
+    "Expected ':' after property name in JSON at position %")                  \
+  T(JsonParseUnterminatedFractionalNumber,                                     \
+    "Unterminated fractional number in JSON at position %")                    \
+  T(JsonParseUnexpectedNonWhiteSpaceCharacter,                                 \
+    "Unexpected non-whitespace character after JSON at position "              \
+    "%")                                                                       \
+  T(JsonParseBadEscapedCharacter,                                              \
+    "Bad escaped character in JSON at position %")                             \
+  T(JsonParseNoNumberAfterMinusSign,                                           \
+    "No number after minus sign in JSON at position %")                        \
+  T(JsonParseShortString, "\"%\" is not valid JSON")                           \
+  T(JsonParseUnexpectedTokenShortString,                                       \
+    "Unexpected token '%', \"%\" is not valid JSON")                           \
+  T(JsonParseUnexpectedTokenSurroundStringWithContext,                         \
+    "Unexpected token '%', ...\"%\"... is not valid JSON")                     \
+  T(JsonParseUnexpectedTokenEndStringWithContext,                              \
+    "Unexpected token '%', ...\"%\" is not valid JSON")                        \
+  T(JsonParseUnexpectedTokenStartStringWithContext,                            \
+    "Unexpected token '%', \"%\"... is not valid JSON")                        \
   T(LabelRedeclaration, "Label '%' has already been declared")                 \
   T(LabelledFunctionDeclaration,                                               \
     "Labelled function declaration not allowed as the body of a control flow " \

src/json/json-parser.cc

@@ -240,20 +240,75 @@ JsonParser<Char>::JsonParser(Isolate* isolate, Handle<String> source)
 }
 
 template <typename Char>
-void JsonParser<Char>::ReportUnexpectedToken(JsonToken token) {
-  // Some exception (for example stack overflow) is already pending.
-  if (isolate_->has_pending_exception()) return;
-
-  // Parse failed. Current character is the unexpected token.
-  Factory* factory = this->factory();
-  MessageTemplate message;
+bool JsonParser<Char>::IsSpecialString() {
+  // The special cases are undefined, NaN, Infinity, and {} being passed to the
+  // parse method
   int offset = original_source_->IsSlicedString()
                    ? SlicedString::cast(*original_source_).offset()
                    : 0;
-  int pos = position() - offset;
-  Handle<Object> arg1 = Handle<Smi>(Smi::FromInt(pos), isolate());
-  Handle<Object> arg2;
+  size_t length = original_source_->length();
+#define CASES(V)       \
+  V("[object Object]") \
+  V("undefined")       \
+  V("Infinity")        \
+  V("NaN")
+  switch (length) {
+#define CASE(n)          \
+  case arraysize(n) - 1: \
+    return CompareCharsEqual(chars_ + offset, n, arraysize(n) - 1);
+    CASES(CASE)
+    default:
+      return false;
+  }
+#undef CASE
+#undef CASES
+}
+
+template <typename Char>
+MessageTemplate JsonParser<Char>::GetErrorMessageWithEllipses(
+    Handle<Object>& arg, Handle<Object>& arg2, int pos) {
+  MessageTemplate message;
+  Factory* factory = this->factory();
+  arg = factory->LookupSingleCharacterStringFromCode(*cursor_);
+  int origin_source_length = original_source_->length();
+  // only provide context for strings with at least
+  // kMinOriginalSourceLengthForContext charcacters in length
+  if (origin_source_length >= kMinOriginalSourceLengthForContext) {
+    int substring_start = 0;
+    int substring_end = origin_source_length;
+    if (pos < kMaxContextCharacters) {
+      message =
+          MessageTemplate::kJsonParseUnexpectedTokenStartStringWithContext;
+      // Output the string followed by elipses
+      substring_end = pos + kMaxContextCharacters;
+    } else if (pos >= kMaxContextCharacters &&
+               pos < origin_source_length - kMaxContextCharacters) {
+      message =
+          MessageTemplate::kJsonParseUnexpectedTokenSurroundStringWithContext;
+      // Add context before and after position of bad token surrounded by
+      // elipses
+      substring_start = pos - kMaxContextCharacters;
+      substring_end = pos + kMaxContextCharacters;
+    } else {
+      message = MessageTemplate::kJsonParseUnexpectedTokenEndStringWithContext;
+      // Add ellipses followed by some context before bad token
+      substring_start = pos - kMaxContextCharacters;
+    }
+    arg2 =
+        factory->NewSubString(original_source_, substring_start, substring_end);
+  } else {
+    arg2 = original_source_;
+    // Output the entire string without ellipses but provide the token which
+    // was unexpected
+    message = MessageTemplate::kJsonParseUnexpectedTokenShortString;
+  }
+  return message;
+}
 
+template <typename Char>
+MessageTemplate JsonParser<Char>::LookUpErrorMessageForJsonToken(
+    JsonToken token, Handle<Object>& arg, Handle<Object>& arg2, int pos) {
+  MessageTemplate message;
   switch (token) {
     case JsonToken::EOS:
       message = MessageTemplate::kJsonParseUnexpectedEOS;
@@ -265,11 +320,36 @@ void JsonParser<Char>::ReportUnexpectedToken(JsonToken token) {
       message = MessageTemplate::kJsonParseUnexpectedTokenString;
       break;
     default:
-      message = MessageTemplate::kJsonParseUnexpectedToken;
-      arg2 = arg1;
-      arg1 = factory->LookupSingleCharacterStringFromCode(*cursor_);
-      break;
+      // Output entire string without ellipses and don't provide the token
+      // that was unexpected because it makes the error messages more confusing
+      if (IsSpecialString()) {
+        arg = original_source_;
+        message = MessageTemplate::kJsonParseShortString;
+      } else {
+        message = GetErrorMessageWithEllipses(arg, arg2, pos);
+      }
   }
+  return message;
+}
+
+template <typename Char>
+void JsonParser<Char>::ReportUnexpectedToken(
+    JsonToken token, base::Optional<MessageTemplate> errorMessage) {
+  // Some exception (for example stack overflow) is already pending.
+  if (isolate_->has_pending_exception()) return;
+
+  // Parse failed. Current character is the unexpected token.
+  Factory* factory = this->factory();
+  int offset = original_source_->IsSlicedString()
+                   ? SlicedString::cast(*original_source_).offset()
+                   : 0;
+  int pos = position() - offset;
+  Handle<Object> arg(Smi::FromInt(pos), isolate());
+  Handle<Object> arg2;
+
+  MessageTemplate message =
+      errorMessage ? errorMessage.value()
+                   : LookUpErrorMessageForJsonToken(token, arg, arg2, pos);
 
   Handle<Script> script(factory->NewScript(original_source_));
   if (isolate()->NeedsSourcePositionsForProfiling()) {
@@ -290,7 +370,7 @@ void JsonParser<Char>::ReportUnexpectedToken(JsonToken token) {
   // separated source file.
   isolate()->debug()->OnCompileError(script);
   MessageLocation location(script, pos, pos + 1);
-  isolate()->ThrowAt(factory->NewSyntaxError(message, arg1, arg2), &location);
+  isolate()->ThrowAt(factory->NewSyntaxError(message, arg, arg2), &location);
 
   // Move the cursor to the end so we won't be able to proceed parsing.
   cursor_ = end_;
@@ -325,7 +405,9 @@ JsonParser<Char>::~JsonParser() {
 template <typename Char>
 MaybeHandle<Object> JsonParser<Char>::ParseJson() {
   MaybeHandle<Object> result = ParseJsonValue();
-  if (!Check(JsonToken::EOS)) ReportUnexpectedToken(peek());
+  if (!Check(JsonToken::EOS))
+    ReportUnexpectedToken(
+        peek(), MessageTemplate::kJsonParseUnexpectedNonWhiteSpaceCharacter);
   if (isolate_->has_pending_exception()) return MaybeHandle<Object>();
   return result;
 }
@@ -751,10 +833,12 @@ MaybeHandle<Object> JsonParser<Char>::ParseJsonValue() {
                                   property_stack.size());
 
           // Parse the property key.
-          ExpectNext(JsonToken::STRING);
+          ExpectNext(JsonToken::STRING,
+                     MessageTemplate::kJsonParseExpectedPropNameOrRBrace);
           property_stack.emplace_back(ScanJsonPropertyKey(&cont));
 
-          ExpectNext(JsonToken::COLON);
+          ExpectNext(JsonToken::COLON,
+                     MessageTemplate::kJsonParseExpectedColonAfterPropertyName);
 
           // Continue to start producing the first property value.
           continue;
@@ -829,7 +913,9 @@ MaybeHandle<Object> JsonParser<Char>::ParseJsonValue() {
 
           if (V8_LIKELY(Check(JsonToken::COMMA))) {
             // Parse the property key.
-            ExpectNext(JsonToken::STRING);
+            ExpectNext(
+                JsonToken::STRING,
+                MessageTemplate::kJsonParseExpectedDoubleQuotedPropertyName);
 
             property_stack.emplace_back(ScanJsonPropertyKey(&cont));
             ExpectNext(JsonToken::COLON);
@@ -855,7 +941,8 @@ MaybeHandle<Object> JsonParser<Char>::ParseJsonValue() {
           }
           value = BuildJsonObject(cont, property_stack, feedback);
           property_stack.resize_no_init(cont.index);
-          Expect(JsonToken::RBRACE);
+          Expect(JsonToken::RBRACE,
+                 MessageTemplate::kJsonParseExpectedCommaOrRBrace);
 
           // Return the object.
           value = cont.scope.CloseAndEscape(value);
@@ -874,7 +961,8 @@ MaybeHandle<Object> JsonParser<Char>::ParseJsonValue() {
 
           value = BuildJsonArray(cont, element_stack);
           element_stack.resize_no_init(cont.index);
-          Expect(JsonToken::RBRACK);
+          Expect(JsonToken::RBRACK,
+                 MessageTemplate::kJsonParseExpectedCommaOrRBrack);
 
           // Return the array.
           value = cont.scope.CloseAndEscape(value);
@@ -933,7 +1021,9 @@ Handle<Object> JsonParser<Char>::ParseJsonNumber() {
       AdvanceToNonDecimal();
       if (V8_UNLIKELY(smi_start == cursor_)) {
         AllowGarbageCollection allow_before_exception;
-        ReportUnexpectedCharacter(CurrentCharacter());
+        ReportUnexpectedToken(
+            JsonToken::ILLEGAL,
+            MessageTemplate::kJsonParseNoNumberAfterMinusSign);
         return handle(Smi::FromInt(0), isolate_);
       }
       c = CurrentCharacter();
@@ -959,7 +1049,9 @@ Handle<Object> JsonParser<Char>::ParseJsonNumber() {
       c = NextCharacter();
       if (!IsDecimalDigit(c)) {
         AllowGarbageCollection allow_before_exception;
-        ReportUnexpectedCharacter(c);
+        ReportUnexpectedToken(
+            JsonToken::ILLEGAL,
+            MessageTemplate::kJsonParseUnterminatedFractionalNumber);
         return handle(Smi::FromInt(0), isolate_);
       }
       AdvanceToNonDecimal();
@@ -970,7 +1062,9 @@ Handle<Object> JsonParser<Char>::ParseJsonNumber() {
       if (c == '-' || c == '+') c = NextCharacter();
       if (!IsDecimalDigit(c)) {
         AllowGarbageCollection allow_before_exception;
-        ReportUnexpectedCharacter(c);
+        ReportUnexpectedToken(
+            JsonToken::ILLEGAL,
+            MessageTemplate::kJsonParseExponentPartMissingNumber);
         return handle(Smi::FromInt(0), isolate_);
       }
       AdvanceToNonDecimal();
@@ -1137,7 +1231,8 @@ JsonString JsonParser<Char>::ScanJsonString(bool needs_internalization) {
 
     if (V8_UNLIKELY(is_at_end())) {
       AllowGarbageCollection allow_before_exception;
-      ReportUnexpectedCharacter(kEndOfString);
+      ReportUnexpectedToken(JsonToken::ILLEGAL,
+                            MessageTemplate::kJsonParseUnterminatedString);
       break;
     }
 
@@ -1188,7 +1283,8 @@ JsonString JsonParser<Char>::ScanJsonString(bool needs_internalization) {
 
         case EscapeKind::kIllegal:
           AllowGarbageCollection allow_before_exception;
-          ReportUnexpectedCharacter(c);
+          ReportUnexpectedToken(JsonToken::ILLEGAL,
+                                MessageTemplate::kJsonParseBadEscapedCharacter);
           return JsonString();
       }
 

src/json/json-parser.h

@@ -211,17 +211,21 @@ class JsonParser final {
     advance();
   }
 
-  void Expect(JsonToken token) {
+  void Expect(JsonToken token,
+              base::Optional<MessageTemplate> errorMessage = base::nullopt) {
     if (V8_LIKELY(peek() == token)) {
       advance();
     } else {
-      ReportUnexpectedToken(peek());
+      errorMessage ? ReportUnexpectedToken(peek(), errorMessage.value())
+                   : ReportUnexpectedToken(peek());
     }
   }
 
-  void ExpectNext(JsonToken token) {
+  void ExpectNext(
+      JsonToken token,
+      base::Optional<MessageTemplate> errorMessage = base::nullopt) {
     SkipWhitespace();
-    Expect(token);
+    errorMessage ? Expect(token, errorMessage.value()) : Expect(token);
   }
 
   bool Check(JsonToken token) {
@@ -301,10 +305,22 @@ class JsonParser final {
       const JsonContinuation& cont,
       const SmallVector<Handle<Object>>& element_stack);
 
+  static const int kMaxContextCharacters = 10;
+  static const int kMinOriginalSourceLengthForContext =
+      (kMaxContextCharacters * 2) + 1;
+
   // Mark that a parsing error has happened at the current character.
   void ReportUnexpectedCharacter(base::uc32 c);
+  bool IsSpecialString();
+  MessageTemplate GetErrorMessageWithEllipses(Handle<Object>& arg,
+                                              Handle<Object>& arg2, int pos);
+  MessageTemplate LookUpErrorMessageForJsonToken(JsonToken token,
+                                                 Handle<Object>& arg,
+                                                 Handle<Object>& arg2, int pos);
   // Mark that a parsing error has happened at the current token.
-  void ReportUnexpectedToken(JsonToken token);
+  void ReportUnexpectedToken(
+      JsonToken token,
+      base::Optional<MessageTemplate> errorMessage = base::nullopt);
 
   inline Isolate* isolate() { return isolate_; }
   inline Factory* factory() { return isolate_->factory(); }

test/inspector/runtime/regress-1078205-expected.txt

@@ -6,7 +6,7 @@ Test malformed sourceURL magic comment.
             columnNumber : 0
             exception : {
                 className : SyntaxError
-                description : SyntaxError: Unexpected token / in JSON at position 0     at JSON.parse (<anonymous>)     at <anonymous>:1:6
+                description : SyntaxError: Unexpected token '/', "//" is not valid JSON     at JSON.parse (<anonymous>)     at <anonymous>:1:6
                 objectId : <objectId>
                 subtype : error
                 type : object
@@ -18,7 +18,7 @@ Test malformed sourceURL magic comment.
         }
         result : {
             className : SyntaxError
-            description : SyntaxError: Unexpected token / in JSON at position 0     at JSON.parse (<anonymous>)     at <anonymous>:1:6
+            description : SyntaxError: Unexpected token '/', "//" is not valid JSON     at JSON.parse (<anonymous>)     at <anonymous>:1:6
             objectId : <objectId>
             subtype : error
             type : object
@@ -32,7 +32,7 @@ Test malformed sourceURL magic comment.
             columnNumber : 0
             exception : {
                 className : SyntaxError
-                description : SyntaxError: Unexpected token / in JSON at position 0     at JSON.parse (<anonymous>)     at <anonymous>:1:6
+                description : SyntaxError: Unexpected token '/', "//#" is not valid JSON     at JSON.parse (<anonymous>)     at <anonymous>:1:6
                 objectId : <objectId>
                 subtype : error
                 type : object
@@ -44,7 +44,7 @@ Test malformed sourceURL magic comment.
         }
         result : {
             className : SyntaxError
-            description : SyntaxError: Unexpected token / in JSON at position 0     at JSON.parse (<anonymous>)     at <anonymous>:1:6
+            description : SyntaxError: Unexpected token '/', "//#" is not valid JSON     at JSON.parse (<anonymous>)     at <anonymous>:1:6
             objectId : <objectId>
             subtype : error
             type : object
@@ -58,7 +58,7 @@ Test malformed sourceURL magic comment.
             columnNumber : 0
             exception : {
                 className : SyntaxError
-                description : SyntaxError: Unexpected token / in JSON at position 0     at JSON.parse (<anonymous>)     at <anonymous>:1:6
+                description : SyntaxError: Unexpected token '/', "//# " is not valid JSON     at JSON.parse (<anonymous>)     at <anonymous>:1:6
                 objectId : <objectId>
                 subtype : error
                 type : object
@@ -70,7 +70,7 @@ Test malformed sourceURL magic comment.
         }
         result : {
             className : SyntaxError
-            description : SyntaxError: Unexpected token / in JSON at position 0     at JSON.parse (<anonymous>)     at <anonymous>:1:6
+            description : SyntaxError: Unexpected token '/', "//# " is not valid JSON     at JSON.parse (<anonymous>)     at <anonymous>:1:6
             objectId : <objectId>
             subtype : error
             type : object
@@ -84,7 +84,7 @@ Test malformed sourceURL magic comment.
             columnNumber : 0
             exception : {
                 className : SyntaxError
-                description : SyntaxError: Unexpected token / in JSON at position 0     at JSON.parse (<anonymous>)     at <anonymous>:1:6
+                description : SyntaxError: Unexpected token '/', "//# sourceURL" is not valid JSON     at JSON.parse (<anonymous>)     at <anonymous>:1:6
                 objectId : <objectId>
                 subtype : error
                 type : object
@@ -96,7 +96,7 @@ Test malformed sourceURL magic comment.
         }
         result : {
             className : SyntaxError
-            description : SyntaxError: Unexpected token / in JSON at position 0     at JSON.parse (<anonymous>)     at <anonymous>:1:6
+            description : SyntaxError: Unexpected token '/', "//# sourceURL" is not valid JSON     at JSON.parse (<anonymous>)     at <anonymous>:1:6
             objectId : <objectId>
             subtype : error
             type : object
@@ -110,7 +110,7 @@ Test malformed sourceURL magic comment.
             columnNumber : 0
             exception : {
                 className : SyntaxError
-                description : SyntaxError: Unexpected token / in JSON at position 0     at JSON.parse (<anonymous>)     at <anonymous>:1:6
+                description : SyntaxError: Unexpected token '/', "//# sourceURL=" is not valid JSON     at JSON.parse (<anonymous>)     at <anonymous>:1:6
                 objectId : <objectId>
                 subtype : error
                 type : object
@@ -122,7 +122,7 @@ Test malformed sourceURL magic comment.
         }
         result : {
             className : SyntaxError
-            description : SyntaxError: Unexpected token / in JSON at position 0     at JSON.parse (<anonymous>)     at <anonymous>:1:6
+            description : SyntaxError: Unexpected token '/', "//# sourceURL=" is not valid JSON     at JSON.parse (<anonymous>)     at <anonymous>:1:6
             objectId : <objectId>
             subtype : error
             type : object
@@ -136,7 +136,7 @@ Test malformed sourceURL magic comment.
             columnNumber : 0
             exception : {
                 className : SyntaxError
-                description : SyntaxError: Unexpected token / in JSON at position 0     at JSON.parse (<anonymous>)     at <anonymous>:1:6
+                description : SyntaxError: Unexpected token '/', "//# sourceURL="" is not valid JSON     at JSON.parse (<anonymous>)     at <anonymous>:1:6
                 objectId : <objectId>
                 subtype : error
                 type : object
@@ -148,10 +148,10 @@ Test malformed sourceURL magic comment.
         }
         result : {
             className : SyntaxError
-            description : SyntaxError: Unexpected token / in JSON at position 0     at JSON.parse (<anonymous>)     at <anonymous>:1:6
+            description : SyntaxError: Unexpected token '/', "//# sourceURL="" is not valid JSON     at JSON.parse (<anonymous>)     at <anonymous>:1:6
             objectId : <objectId>
             subtype : error
             type : object
         }
     }
-}
+}
\ No newline at end of file

test/message/fail/modules-import-assertions-fail-2.out

-undefined:1: SyntaxError: Unexpected token / in JSON at position 0
+undefined:1: SyntaxError: Unexpected token '/', "// Copyrig"... is not valid JSON
 // Copyright 2021 the V8 project authors. All rights reserved.
 ^
-SyntaxError: Unexpected token / in JSON at position 0
\ No newline at end of file
+SyntaxError: Unexpected token '/', "// Copyrig"... is not valid JSON
\ No newline at end of file

test/mjsunit/json-errors.js

@@ -12,19 +12,19 @@ function TryParse(s, message) {
 }
 
 var s = `{"a\\\\b `;
-TryParse(s, "Unexpected end of JSON input");
+TryParse(s, "Unterminated string in JSON at position 7");
 
 var s = `{"a\\\\\u03A9 `;
-TryParse(s, "Unexpected end of JSON input");
+TryParse(s, "Unterminated string in JSON at position 7");
 
 var s = `{"ab `;
-TryParse(s, "Unexpected end of JSON input");
+TryParse(s, "Unterminated string in JSON at position 5");
 
 var s = `{"a\u03A9 `;
-TryParse(s, "Unexpected end of JSON input");
+TryParse(s, "Unterminated string in JSON at position 5");
 
 var s = `{"a\nb":"b"}`;
-TryParse(s, "Unexpected token \n in JSON at position 3");
+TryParse(s, "Unexpected token '\n', \"{\"a\nb\":\"b\"}\" is not valid JSON");
 
 var s = `{"a\nb":"b\u03A9"}`;
-TryParse(s, "Unexpected token \n in JSON at position 3");
+TryParse(s, "Unexpected token '\n', \"{\"a\nb\":\"b\u03A9\"}\" is not valid JSON");

test/mjsunit/messages.js

@@ -474,25 +474,129 @@ test(function() {
   eval("'\n'");
 }, "Invalid or unexpected token", SyntaxError);
 
-//kJsonParseUnexpectedEOS
+// kJsonParseUnterminatedString
+test(function() {
+  JSON.parse('{"a" : "}')
+}, "Unterminated string in JSON at position 9", SyntaxError);
+
+// kJsonParseExpectedPropNameOrRBrace
 test(function() {
   JSON.parse("{")
-}, "Unexpected end of JSON input", SyntaxError);
+}, "Expected property name or '}' in JSON at position 1", SyntaxError);
+
+// kJsonParseExpectedDoubleQuotedPropertyName
+test(function() {
+  JSON.parse('{"foo" : 1, }');
+}, "Expected double-quoted property name in JSON at position 12", SyntaxError);
+
+// kJsonParseExpectedCommaNameOrRBrack
+test(function() {
+  JSON.parse("{'foo': 1}");
+}, "Expected property name or '}' in JSON at position 1", SyntaxError);
+
+// kJsonParseExpectedCommaNameOrRBrace
+test(function() {
+  JSON.parse('[1, 2, 3, 4');
+}, "Expected ',' or ']' after array element in JSON at position 11", SyntaxError);
+
+test(function() {
+  JSON.parse('[1, 2, 3, 4g');
+}, "Expected ',' or ']' after array element in JSON at position 11", SyntaxError);
 
-// kJsonParseUnexpectedTokenAt
+// kJsonParseExponentPartMissingNumber
+test(function() {
+  JSON.parse('[1e]');
+}, "Exponent part is missing a number in JSON at position 3", SyntaxError);
+
+// kJsonParseExpectedColonAfterPropertyName
+test(function() {
+  JSON.parse('{"a"}');
+}, "Expected ':' after property name in JSON at position 4", SyntaxError);
+
+// kJsonParseUnterminatedFractionNumber
+test(function() {
+  JSON.parse('{"a": 0.bs}');
+}, "Unterminated fractional number in JSON at position 8", SyntaxError);
+
+// kJsonParseUnexpectedNonWhiteSpaceCharacter
+test(function() {
+  JSON.parse('{"a": 3}a');
+}, "Unexpected non-whitespace character after JSON at position 8", SyntaxError);
+
+// kJsonParseBadEscapedCharacter
+test(function() {
+  JSON.parse('{"b" : "\\a"}');
+}, "Bad escaped character in JSON at position 9", SyntaxError);
+
+// kJsonParseNoNumberAfterMinusSign
+test(function() {
+  JSON.parse('-');
+}, "No number after minus sign in JSON at position 1", SyntaxError);
+
+// kJsonParseUnexpectedTokenShortString
+test(function () {
+  JSON.parse(NaN)
+}, "\"NaN\" is not valid JSON", SyntaxError);
+
+// kJsonParseUnexpectedTokenShortString
 test(function() {
   JSON.parse("/")
-}, "Unexpected token / in JSON at position 0", SyntaxError);
+}, "Unexpected token '/', \"/\" is not valid JSON", SyntaxError);
+
+// kJsonParseUnexpectedTokenShortString
+test(function () {
+  JSON.parse(undefined)
+}, "\"undefined\" is not valid JSON", SyntaxError);
 
-// kJsonParseUnexpectedTokenNumberAt
+// kJsonParseUnexpectedTokenShortString
+test(function () {
+  JSON.parse(Infinity)
+}, "\"Infinity\" is not valid JSON", SyntaxError);
+
+// kJsonParseUnexpectedTokenShortString
+test(function () {
+  JSON.parse('Bad string')
+}, "Unexpected token 'B', \"Bad string\" is not valid JSON", SyntaxError);
+
+// kJsonParseUnexpectedTokenShortString
+test(function () {
+  JSON.parse({})
+}, "\"[object Object]\" is not valid JSON", SyntaxError);
+
+// kJsonParseExpectedPropNameOrRBrace
 test(function() {
   JSON.parse("{ 1")
-}, "Unexpected number in JSON at position 2", SyntaxError);
+}, "Expected property name or '}' in JSON at position 2", SyntaxError);
 
-// kJsonParseUnexpectedTokenStringAt
+// kJsonParseUnexpectedNonWhiteSpaceCharacter
 test(function() {
   JSON.parse('"""')
-}, "Unexpected string in JSON at position 2", SyntaxError);
+}, "Unexpected non-whitespace character after JSON at position 2", SyntaxError);
+
+// kJsonParseUnexpectedTokenStringShortString
+test(function() {
+  JSON.parse('[1, 2,]');
+}, "Unexpected token ']', \"[1, 2,]\" is not valid JSON", SyntaxError);
+
+// kJsonParseUnexpectedTokenStringShortString
+test(function() {
+  JSON.parse('[1, 2, 3, 4, ]');
+}, "Unexpected token ']', \"[1, 2, 3, 4, ]\" is not valid JSON", SyntaxError);
+
+// kJsonParseUnexpectedTokenStringSurroundWithContext
+test(function() {
+  JSON.parse('[1, 2, 3, 4, 5, , 7, 8, 9, 10]');
+}, "Unexpected token ',', ...\" 3, 4, 5, , 7, 8, 9,\"... is not valid JSON", SyntaxError);
+
+// kJsonParseUnexpectedTokenStringStartWithContext
+test(function() {
+  JSON.parse('[, 2, 3, 4, 5, 6, 7, 8, 9, 10]');
+}, "Unexpected token ',', \"[, 2, 3, 4,\"... is not valid JSON", SyntaxError);
+
+// kJsonParseUnexpectedTokenStringEndWithContext
+test(function() {
+  JSON.parse('[1, 2, 3, 4, 5, 6, 7, ]');
+}, "Unexpected token ']', ...\" 5, 6, 7, ]\" is not valid JSON", SyntaxError);
 
 // kMalformedRegExp
 test(function() {