ShaderBuildProcessor.cs

using System.Collections.Generic;
using UnityEditor;
using UnityEditor.Build;
using UnityEditor.Rendering;
using UnityEngine;
using UnityEngine.Rendering;

class ShaderBuildProcessor : IPreprocessShaders
{
    ShaderVariantCollection whitelist;

    public ShaderBuildProcessor()
    {
        var whitelistAsset = AssetDatabase.LoadAssetAtPath<ShaderVariantCollection>("Assets/Editor/ShaderBuilding/ShaderWhitelist.shadervariants");
        if (whitelistAsset == null)
        {
        	Debug.LogError("Can't find shader whitelist");
        	return;
        }
        whitelist = whitelistAsset as ShaderVariantCollection;
        if (whitelist == null)
        {
        	Debug.LogError("Can't cast shader whitelist");
        	return;
        }
    }

    public int callbackOrder { get { return 0; } }

    public void OnProcessShader(Shader shader, ShaderSnippetData snippet, IList<ShaderCompilerData> data)
    {
    	if (whitelist == null) return;
    	var shaderVar = new ShaderVariantCollection.ShaderVariant();
    	shaderVar.shader = shader;
    	shaderVar.passType = snippet.passType;
    	int skipped = 0;
        for (int i = data.Count - 1; i >= 0; --i)
        {
        	var keywordSet = data[i].shaderKeywordSet.GetShaderKeywords();
        	var keywords = new List<string>();
        	for(int j=0; j<keywordSet.Length; j++)
        	{
        		var keywordName = ShaderKeyword.GetKeywordName(shader, keywordSet[j]);
        		keywords.Add(keywordName);
        	}
        	shaderVar.keywords = keywords.ToArray();

        	if (!whitelist.Contains(shaderVar))
        	{
        		skipped++;
            	data.RemoveAt(i);
            }
        }
        Debug.Log("Skipped " + skipped + " variants of " + shader.name + " (" + snippet.passType + ")");
    }
}