Merge pull request #1252 from Unity-Technologies/lw/shader-keywords-stripping-v2

Stripped invalid variants.

ScriptableRenderPipeline/LightweightPipeline/LWRP/Editor/ShaderPreprocessor.cs

             return false;
         }
 
+        bool StripInvalidVariants(ShaderCompilerData compilerData)
+        {
+            bool isShadowVariant = compilerData.shaderKeywordSet.IsEnabled(LightweightKeywords.DirectionalShadows) ||
+                compilerData.shaderKeywordSet.IsEnabled(LightweightKeywords.LocalShadows);
+
+            if (compilerData.shaderKeywordSet.IsEnabled(LightweightKeywords.SoftShadows) && !isShadowVariant)
+                return true;
+
+            if (compilerData.shaderKeywordSet.IsEnabled(LightweightKeywords.VertexLights) &&
+                !compilerData.shaderKeywordSet.IsEnabled(LightweightKeywords.AdditionalLights))
+                return true;
+
+            // Note: LWRP doesn't support Dynamic Lightmap.
+            if (compilerData.shaderKeywordSet.IsEnabled(LightweightKeywords.DirectionalLightmap) &&
+                !compilerData.shaderKeywordSet.IsEnabled(LightweightKeywords.Lightmap))
+                return true;
+
+            return false;
+        }
+
         bool StripUnused(PipelineCapabilities capabilities, Shader shader, ShaderSnippetData snippetData, ShaderCompilerData compilerData)
         {
             if (StripUnusedShader(capabilities, shader))
                 return true;
 
             if (StripUnusedVariant(capabilities, compilerData))
+                return true;
+
+            if (StripInvalidVariants(compilerData))
                 return true;
 
             return false;

ScriptableRenderPipeline/LightweightPipeline/LWRP/LightweightPipelineCore.cs

         public static readonly ShaderKeyword DirectionalShadows = new ShaderKeyword(DirectionalShadowsText);
         public static readonly ShaderKeyword LocalShadows = new ShaderKeyword(LocalShadowsText);
         public static readonly ShaderKeyword SoftShadows = new ShaderKeyword(SoftShadowsText);
+
+        public static readonly ShaderKeyword Lightmap = new ShaderKeyword("LIGHTMAP_ON");
+        public static readonly ShaderKeyword DirectionalLightmap = new ShaderKeyword("DIRLIGHTMAP_COMBINED");
     }
 
     public partial class LightweightPipeline