update exceptions.hpp to use the diagnostic positions

Signed-off-by: Harinath Nampally <harinath922@gmail.com>

docs/examples/diagnostic_positions.cpp

@@ -5,6 +5,30 @@
 
 using json = nlohmann::json;
 
+/* Demonstration of type error exception with diagnostic postions support enabled */
+void type_error_exception()
+{
+    //Invalid json string - housenumber type must be int instead of string
+    std::string json_invalid_string = R"(
+    {
+        "address": {
+            "street": "Fake Street",
+            "housenumber": "1"
+        }
+    }
+    )";
+    json j = json::parse(json_invalid_string);
+    try
+    {
+        int housenumber = j["address"]["housenumber"];
+    }
+    catch (const json::exception& e)
+    {
+        std::cout << e.what() << '\n';
+    }
+
+}
+
 int main()
 {
     std::string json_string = R"(
@@ -48,4 +72,7 @@ int main()
     std::cout << "1" << "\n";
     std::cout << "Parsed string: \n";
     std::cout << json_string.substr(j["address"]["housenumber"].start_pos(), j["address"]["housenumber"].end_pos() - j["address"]["housenumber"].start_pos()) << "\n\n";
+
+    type_error_exception();
+
 }

docs/examples/diagnostic_positions.output

@@ -48,3 +48,4 @@ Original string:
 Parsed string: 
 1
 
+[json.exception.type_error.302] (byte 92-95) type must be number, but is string

docs/examples/diagnostics_extended.cpp

@@ -1,15 +1,22 @@
 #include <iostream>
 
 # define JSON_DIAGNOSTICS 1
+# define JSON_DIAGNOSTIC_POSITIONS 1
 #include <nlohmann/json.hpp>
 
 using json = nlohmann::json;
 
 int main()
 {
-    json j;
-    j["address"]["street"] = "Fake Street";
-    j["address"]["housenumber"] = "12";
+    std::string json_string = R"(
+    {
+        "address": {
+            "street": "Fake Street",
+            "housenumber": "12"
+        }
+    }
+    )";
+    json j = json::parse(json_string);
 
     try
     {

docs/examples/diagnostics_extended.output

@@ -1 +1 @@
-[json.exception.type_error.302] (/address/housenumber) type must be number, but is string
+[json.exception.type_error.302] (/address/housenumber, byte 92-96) type must be number, but is string

include/nlohmann/detail/exceptions.hpp

@@ -107,7 +107,6 @@ class exception : public std::exception
                     }
                     break;
                 }
-
                 case value_t::null: // LCOV_EXCL_LINE
                 case value_t::string: // LCOV_EXCL_LINE
                 case value_t::boolean: // LCOV_EXCL_LINE
@@ -131,6 +130,12 @@ class exception : public std::exception
         {
             return concat(a, '/', detail::escape(b));
         });
+#if JSON_DIAGNOSTIC_POSITIONS
+        str += ", byte " + std::to_string(leaf_element->start_pos()) + "-" + std::to_string(leaf_element->end_pos());
+#endif
+        return concat('(', str, ") ");
+#elif JSON_DIAGNOSTIC_POSITIONS
+        auto str = "byte " + std::to_string(leaf_element->start_pos()) + "-" + std::to_string(leaf_element->end_pos());
         return concat('(', str, ") ");
 #else
         static_cast<void>(leaf_element);

single_include/nlohmann/json.hpp

@@ -4510,7 +4510,6 @@ class exception : public std::exception
                     }
                     break;
                 }
-
                 case value_t::null: // LCOV_EXCL_LINE
                 case value_t::string: // LCOV_EXCL_LINE
                 case value_t::boolean: // LCOV_EXCL_LINE
@@ -4534,6 +4533,12 @@ class exception : public std::exception
         {
             return concat(a, '/', detail::escape(b));
         });
+#if JSON_DIAGNOSTIC_POSITIONS
+        str += ", byte " + std::to_string(leaf_element->start_pos()) + "-" + std::to_string(leaf_element->end_pos());
+#endif
+        return concat('(', str, ") ");
+#elif JSON_DIAGNOSTIC_POSITIONS
+        auto str = "byte " + std::to_string(leaf_element->start_pos()) + "-" + std::to_string(leaf_element->end_pos());
         return concat('(', str, ") ");
 #else
         static_cast<void>(leaf_element);