STAT-273: Fix json parsing issues

(cherry picked from commit 9aa838e9)

libraries/fc/src/io/json.cpp

@@ -96,9 +96,8 @@ namespace fc
                                             "Expected '\"' but read '${char}'",
                                             ("char", string(&c, (&c) + 1) ) );
          in.get();
-         while( true )
+         while( !in.eof() )
          {
-
             switch( c = in.peek() )
             {
                case '\\':
@@ -128,7 +127,7 @@ namespace fc
       {
          char c = in.peek();
 
-         while( true )
+         while( !in.eof() )
          {
             switch( c = in.peek() )
             {

tests/tests/misc_tests.cpp

@@ -22,6 +22,26 @@ using namespace std;
 
 BOOST_AUTO_TEST_SUITE(misc_tests)
 
+/// Test processing of unbalanced strings
+BOOST_AUTO_TEST_CASE(json_from_string_test)
+{
+  bool exc_found = false;
+  try {
+    auto val = fc::json::from_string("{\"}");
+  } catch(...) {
+    exc_found = true;
+  }
+  BOOST_CHECK_EQUAL(exc_found, true);
+
+  exc_found = false;
+  try {
+    auto val = fc::json::from_string("{\"block_num_or_id\":5");
+  } catch(...) {
+    exc_found = true;
+  }
+  BOOST_CHECK_EQUAL(exc_found, true);
+}
+
 /// Test calculation of median values of blockchain operation properties
 BOOST_AUTO_TEST_CASE(median_properties_test)
 { try {