Add more diagnostics to intermittently failing assert (#68414)

Author: krwq

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/JsonPropertyInfo.cs

@@ -338,6 +338,25 @@ private bool NumberHandingIsApplicable()
 
         internal abstract object? GetValueAsObject(object obj);
 
+#if DEBUG
+        internal string GetDebugInfo(int indent = 0)
+        {
+            string ind = new string(' ', indent);
+            StringBuilder sb = new();
+
+            sb.AppendLine($"{ind}{{");
+            sb.AppendLine($"{ind}  Name: {Name},");
+            sb.AppendLine($"{ind}  NameAsUtf8.Length: {(NameAsUtf8Bytes?.Length ?? -1)},");
+            sb.AppendLine($"{ind}  IsConfigured: {_isConfigured},");
+            sb.AppendLine($"{ind}  IsIgnored: {IsIgnored},");
+            sb.AppendLine($"{ind}  ShouldSerialize: {ShouldSerialize},");
+            sb.AppendLine($"{ind}  ShouldDeserialize: {ShouldDeserialize},");
+            sb.AppendLine($"{ind}}}");
+
+            return sb.ToString();
+        }
+#endif
+
         internal bool HasGetter { get; set; }
         internal bool HasSetter { get; set; }
 

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/JsonTypeInfo.Cache.cs

@@ -187,7 +187,14 @@ internal JsonPropertyInfo GetProperty(
                 {
                     if (propertyName.SequenceEqual(info.NameAsUtf8Bytes))
                     {
-                        Debug.Assert(key == GetKey(info.NameAsUtf8Bytes.AsSpan()), "key does not match re-computed value for the same sequence (case-insensitive)");
+#if DEBUG
+                        ulong recomputedKey = GetKey(info.NameAsUtf8Bytes.AsSpan());
+                        if (key != recomputedKey)
+                        {
+                            string propertyNameStr = JsonHelpers.Utf8GetString(propertyName);
+                            Debug.Fail($"key {key} [propertyName={propertyNameStr}] does not match re-computed value {recomputedKey} for the same sequence (case-insensitive). {info.GetDebugInfo()}");
+                        }
+#endif
 
                         // Use the existing byte[] reference instead of creating another one.
                         utf8PropertyName = info.NameAsUtf8Bytes!;
@@ -200,7 +207,14 @@ internal JsonPropertyInfo GetProperty(
                 }
                 else
                 {
-                    Debug.Assert(key == GetKey(info.NameAsUtf8Bytes.AsSpan()), "key does not match re-computed value for the same sequence (case-sensitive)");
+#if DEBUG
+                    ulong recomputedKey = GetKey(info.NameAsUtf8Bytes.AsSpan());
+                    if (key != recomputedKey)
+                    {
+                        string propertyNameStr = JsonHelpers.Utf8GetString(propertyName);
+                        Debug.Fail($"key {key} [propertyName={propertyNameStr}] does not match re-computed value {recomputedKey} for the same sequence (case-sensitive). {info.GetDebugInfo()}");
+                    }
+#endif
                     utf8PropertyName = info.NameAsUtf8Bytes;
                 }
             }

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/JsonTypeInfo.cs

@@ -255,7 +255,7 @@ internal string GetDebugInfo()
             bool propCacheInitialized = PropertyCache != null;
 
             StringBuilder sb = new();
-            sb.AppendLine($"{jtiTypeName} {{");
+            sb.AppendLine("{");
             sb.AppendLine($"  GetType: {jtiTypeName},");
             sb.AppendLine($"  Type: {typeName},");
             sb.AppendLine($"  ConverterStrategy: {strat},");
@@ -268,11 +268,8 @@ internal string GetDebugInfo()
                 foreach (var property in PropertyCache!.List)
                 {
                     JsonPropertyInfo pi = property.Value!;
-                    sb.AppendLine($"    {property.Key}: {{");
-                    sb.AppendLine($"      Ignored: {pi.IsIgnored},");
-                    sb.AppendLine($"      ShouldSerialize: {pi.ShouldSerialize},");
-                    sb.AppendLine($"      ShouldDeserialize: {pi.ShouldDeserialize},");
-                    sb.AppendLine("    },");
+                    sb.AppendLine($"    {property.Key}:");
+                    sb.AppendLine($"{pi.GetDebugInfo(indent: 6)},");
                 }
 
                 sb.AppendLine("  },");