BUG#37243264 Negative BSON values cause util.importJson() to fail

When importing JSON with `convertBsonTypes` option set to true, negative
$numberInt/$numberLong values (or positive value prefixed with the `+`
character) caused the import to fail.

The parser did not skip the `-` and `+` characters when validating the
integer values.

Change-Id: I902774d8781e805db6e6b7c236503a5ff278d67d

Author: Paweł Andruszkiewicz

mysqlshdk/libs/utils/document_parser.cc

@@ -606,7 +606,9 @@ void Json_document_parser::get_bson_data(const std::vector<Bson_token> &tokens,
       // Integers must have pure decimal digits
       if (token.type == 'I' || token.type == 'i') {
         size_t digit_index = 0;
-        if ((*target)[0] == '+' || (*target)[0] == '-') digit_index++;
+        if ((*target)[value_start] == '+' || (*target)[value_start] == '-') {
+          digit_index++;
+        }
 
         for (size_t index = digit_index; index < value_size; index++) {
           if (!isdigit((*target)[value_start + index]))
@@ -717,7 +719,14 @@ void Json_document_parser::parse_bson_integer(Bson_type type) {
 
   get_bson_data({{':'}, {'I', "", &value, nullptr}, {'}'}}, context);
 
-  std::string number = value.substr(1, value.size() - 2);
+  // handle a signed integer starting with a plus, trim the plus character
+  std::size_t start = 1;
+
+  if ('+' == value[start]) {
+    ++start;
+  }
+
+  std::string number = value.substr(start, value.size() - 1 - start);
 
   m_document->append(number);
 }

unittest/scripts/auto/js_shell/scripts/json_import_bson_norecord.js

@@ -223,6 +223,10 @@ EXPECT_STDOUT_CONTAINS("ERROR: Unexpected data, expected to find '}' processing
 import_doc({_id:{$oid:"5bfe3d5ff6d2f36d067c6fea"},int:{$numberInt:""}});
 EXPECT_STDOUT_CONTAINS("ERROR: Unexpected data, expected to find an integer string processing extended JSON for $numberInt at offset 64");
 
+//@<> BUG#37243264 $numberInt with just +
+import_doc({_id:{$oid:"5bfe3d5ff6d2f36d067c6fea"},int:{$numberInt:"+"}});
+EXPECT_STDOUT_CONTAINS("ERROR: Unexpected data, expected to find an integer string processing extended JSON for $numberInt at offset 64");
+
 
 //@<> $numberDecimal with non string value
 import_doc({_id:{$oid:"5bfe3d5ff6d2f36d067c6fea"},decimal:{$numberDecimal:15.4}});
@@ -311,3 +315,15 @@ import_doc(document, ["--convertBsonTypes", "--convertBsonOid=false"])
 print_doc();
 delete_doc();
 EXPECT_STDOUT_CONTAINS('{"_id": "01234567890123456789", "objectId": {"$oid": "5c014aa8087579bdb2e6afef"}, "negativeInteger": -450}');
+
+//@<> BUG#37243264 $numberInt with negative integer
+import_doc({_id:{$oid:"5bfe3d5ff6d2f36d067c6fea"},int:{$numberInt:"-1234"}});
+print_doc();
+delete_doc();
+EXPECT_STDOUT_CONTAINS('{"_id": "5bfe3d5ff6d2f36d067c6fea", "int": -1234}');
+
+//@<> BUG#37243264 $numberInt with positive integer
+import_doc({_id:{$oid:"5bfe3d5ff6d2f36d067c6fea"},int:{$numberInt:"+1234"}});
+print_doc();
+delete_doc();
+EXPECT_STDOUT_CONTAINS('{"_id": "5bfe3d5ff6d2f36d067c6fea", "int": 1234}');