Extend type_name() to invalid type (#4786)

* ✅ add regression test

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 💚 fix build

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* 📝 add comment

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

include/nlohmann/json.hpp

@@ -4206,8 +4206,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             case value_t::number_integer:
             case value_t::number_unsigned:
             case value_t::number_float:
-            default:
                 return "number";
+            default:
+                return "invalid";
         }
     }
 

single_include/nlohmann/json.hpp

@@ -24291,8 +24291,9 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
             case value_t::number_integer:
             case value_t::number_unsigned:
             case value_t::number_float:
-            default:
                 return "number";
+            default:
+                return "invalid";
         }
     }
 

tests/src/unit-regression2.cpp

@@ -1080,6 +1080,20 @@ TEST_CASE("regression tests 2")
         CHECK(t4.port.has_value());
     }
 #endif
+
+#if !defined(_MSVC_LANG)
+    // MSVC returns garbage on invalid enum values, so this test is excluded
+    // there.
+    SECTION("issue #4762 - json exception 302 with unhelpful explanation : type must be number, but is number")
+    {
+        // In #4762, the main issue was that a json object with an invalid type
+        // returned "number" as type_name(), because this was the default case.
+        // This test makes sure we now return "invalid" instead.
+        json j;
+        j.m_data.m_type = static_cast<json::value_t>(100); // NOLINT(clang-analyzer-optin.core.EnumCastOutOfRange)
+        CHECK(j.type_name() == "invalid");
+    }
+#endif
 }
 
 DOCTEST_CLANG_SUPPRESS_WARNING_POP