Added new ToDictionaryWithConflictLog to help diagnose ToDictionary bombs.

OpenRA.FileFormats/Exts.cs

@@ -184,6 +184,58 @@ namespace OpenRA
 			return ts.Concat(moreTs);
 		}
 
+		public static Dictionary<TKey, TSource> ToDictionaryWithConflictLog<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, string debugName, Func<TKey, string> logKey, Func<TSource, string> logValue)
+		{
+			return ToDictionaryWithConflictLog(source, keySelector, x => x, debugName, logKey, logValue);
+		}
+
+		public static Dictionary<TKey, TElement> ToDictionaryWithConflictLog<TSource, TKey, TElement>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, string debugName, Func<TKey, string> logKey, Func<TElement, string> logValue)
+		{
+			// Fall back on ToString() if null functions are provided:
+			logKey = logKey ?? (s => s.ToString());
+			logValue = logValue ?? (s => s.ToString());
+
+			// Try to build a dictionary and log all duplicates found (if any):
+			var dupKeys = new Dictionary<TKey, List<string>>();
+			var d = new Dictionary<TKey, TElement>();
+			foreach (var item in source)
+			{
+				TKey key = keySelector(item);
+				TElement element = elementSelector(item);
+
+				// Check for a key conflict:
+				if (d.ContainsKey(key))
+				{
+					List<string> dupKeyMessages;
+					if (!dupKeys.TryGetValue(key, out dupKeyMessages))
+					{
+						// Log the initial conflicting value already inserted:
+						dupKeyMessages = new List<string>();
+						dupKeyMessages.Add(logValue(d[key]));
+						dupKeys.Add(key, dupKeyMessages);
+					}
+
+					// Log this conflicting value:
+					dupKeyMessages.Add(logValue(element));
+					continue;
+				}
+
+				d.Add(key, element);
+			}
+
+			// If any duplicates were found, log it and throw a descriptive error
+			if (dupKeys.Count > 0)
+			{
+				string badKeysFormatted = String.Join(", ", dupKeys.Select(p => "{0}: [{1}]".F(logKey(p.Key), String.Join(",", p.Value.ToArray()))).ToArray());
+				string msg = "{0}, duplicate values found for the following keys: {1}".F(debugName, badKeysFormatted);
+				Log.Write("debug", msg);
+				throw new ArgumentException(msg);
+			}
+
+			// Return the dictionary we built:
+			return d;
+		}
+
 		public static Color ColorLerp(float t, Color c1, Color c2)
 		{
 			return Color.FromArgb(