[ShaderGraph] Allow nested keyword definitions to generate properly in final shader

Author: Esmeralda Salamone

Packages/com.unity.shadergraph/Editor/Data/Graphs/GraphData.cs

@@ -1371,12 +1371,33 @@ public void CollectShaderProperties(PropertyCollector collector, GenerationMode
             }
         }
 
+        private static void CollectSubgraphKeywordsR(KeywordCollector collector, SubGraphAsset asset)
+        {
+            if (asset is null || !asset.isValid || asset.isNull)
+                return;
+
+            foreach(var keyword in asset.keywords)
+            {
+                collector.AddShaderKeyword(keyword);
+            }
+            foreach(var guid in asset.children)
+            {
+                var path = AssetDatabase.GUIDToAssetPath(guid);
+                var child = AssetDatabase.LoadAssetAtPath<SubGraphAsset>(path);
+                CollectSubgraphKeywordsR(collector, child);
+            }
+        }
+
         public void CollectShaderKeywords(KeywordCollector collector, GenerationMode generationMode)
         {
             foreach (var keyword in keywords)
             {
                 collector.AddShaderKeyword(keyword);
             }
+            foreach(var node in GetNodes<SubGraphNode>())
+            {
+                CollectSubgraphKeywordsR(collector, node.asset);
+            }
 
             // Alwways calculate permutations when collecting
             collector.CalculateKeywordPermutations();

Packages/com.unity.shadergraph/Editor/Data/SubGraph/SubGraphAsset.cs

@@ -83,6 +83,8 @@ class SubGraphAsset : ScriptableObject, ISerializationCallbackReceiver
 
         public string assetGuid;
 
+        public bool isNull => m_SubGraphData == null;
+
         public ShaderGraphRequirements requirements;
 
         public string path;