[mono] new Sdk that selects mono runtime components

src/tasks/JsonToItemsTaskFactory/JsonToItemsTaskFactory.cs

@@ -7,6 +7,7 @@
 using System.IO;
 using System.Text.Json;
 using System.Text.Json.Serialization;
+using System.Threading.Tasks;
 
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
@@ -198,10 +199,11 @@ public bool TryGetJson(string jsonFilePath, [NotNullWhen(true)] out JsonModelRoo
                         json = null;
                         return false;
                     }
-                    json = JsonSerializer.DeserializeAsync<JsonModelRoot>(file, JsonOptions).AsTask().Result;
+                    json = GetJsonAsync(jsonFilePath, file).Result;
                     if (json == null)
                     {
-                        Log.LogError($"Failed to deserialize json from file {jsonFilePath}");
+                        // the async task may have already caught an exception and logged it.
+                        if (!Log.HasLoggedErrors) Log.LogError($"Failed to deserialize json from file {jsonFilePath}");
                         return false;
                     }
                     return true;
@@ -213,6 +215,21 @@ public bool TryGetJson(string jsonFilePath, [NotNullWhen(true)] out JsonModelRoo
                 }
             }
 
+            public async Task<JsonModelRoot?> GetJsonAsync(string jsonFilePath, FileStream file)
+            {
+                JsonModelRoot? json = null;
+                try
+                {
+                    json = await JsonSerializer.DeserializeAsync<JsonModelRoot>(file, JsonOptions).ConfigureAwait(false);
+                }
+                catch (JsonException e)
+                {
+                    Log.LogError($"Failed to deserialize json from file '{jsonFilePath}', JSON Path: {e.Path}, Line: {e.LineNumber}, Position: {e.BytePositionInLine}");
+                    Log.LogErrorFromException(e, showStackTrace: false, showDetail: true, file: null);
+                }
+                return json;
+            }
+
             internal void LogParsedJson (JsonModelRoot json)
             {
                 if (json.Properties != null)
@@ -353,20 +370,20 @@ public override JsonModelItem Read(ref Utf8JsonReader reader, Type typeToConvert
                     case JsonTokenType.String:
                         var stringItem = reader.GetString();
                         if (string.IsNullOrEmpty(stringItem))
-                            throw new Exception ("deserialized json string item was null or the empty string");
+                            throw new JsonException ("deserialized json string item was null or the empty string");
                         return new JsonModelItem(stringItem!, metadata: null);
                     case JsonTokenType.StartObject:
                         var dict = JsonSerializer.Deserialize<Dictionary<string, string>>(ref reader, options);
                         if (dict == null)
                             return null!;
                         var idict = new Dictionary<string, string> (dict, StringComparer.OrdinalIgnoreCase);
                         if  (!idict.TryGetValue("Identity", out var identity) || string.IsNullOrEmpty(identity))
-                            throw new Exception ("deserialized json dictionary item did not have a non-empty Identity metadata");
+                            throw new JsonException ("deserialized json dictionary item did not have a non-empty Identity metadata");
                         else
                             idict.Remove("Identity");
                         return new JsonModelItem(identity, metadata: idict);
                     default:
-                        throw new Exception();
+                        throw new NotSupportedException();
                 }
             }
             public override void Write(Utf8JsonWriter writer, JsonModelItem value, JsonSerializerOptions options)