ScriptableRenderPipeline/com.unity.shadergraph/Editor/Importers/ShaderGraphImporter.cs

using UnityEditor.ShaderGraph;
using UnityEngine;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using UnityEditor;
using UnityEditor.Experimental.AssetImporters;
using UnityEditor.ShaderGraph.Drawing;

[ScriptedImporter(13, ShaderGraphImporter.ShaderGraphExtension)]
public class ShaderGraphImporter : ScriptedImporter
{
    public const string ShaderGraphExtension = "shadergraph";

    const string k_ErrorShader = @"
Shader ""Hidden/GraphErrorShader2""
{
    SubShader
    {
        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma target 2.0
            #pragma multi_compile _ UNITY_SINGLE_PASS_STEREO STEREO_INSTANCING_ON STEREO_MULTIVIEW_ON
            #include ""UnityCG.cginc""

            struct appdata_t {
                float4 vertex : POSITION;
                UNITY_VERTEX_INPUT_INSTANCE_ID
            };

            struct v2f {
                float4 vertex : SV_POSITION;
                UNITY_VERTEX_OUTPUT_STEREO
            };

            v2f vert (appdata_t v)
            {
                v2f o;
                UNITY_SETUP_INSTANCE_ID(v);
                UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(o);
                o.vertex = UnityObjectToClipPos(v.vertex);
                return o;
            }
            fixed4 frag (v2f i) : SV_Target
            {
                return fixed4(1,0,1,1);
            }
            ENDCG
        }
    }
    Fallback Off
}";


    public override void OnImportAsset(AssetImportContext ctx)
    {
        var oldShader = AssetDatabase.LoadAssetAtPath<Shader>(ctx.assetPath);
        if (oldShader != null)
            ShaderUtil.ClearShaderErrors(oldShader);

        List<PropertyCollector.TextureInfo> configuredTextures;
        var text = GetShaderText(ctx.assetPath, out configuredTextures);
        var shader = ShaderUtil.CreateShaderAsset(text);

        EditorMaterialUtility.SetShaderDefaults(
            shader,
            configuredTextures.Where(x => x.modifiable).Select(x => x.name).ToArray(),
            configuredTextures.Where(x => x.modifiable).Select(x => EditorUtility.InstanceIDToObject(x.textureId) as Texture).ToArray());
        EditorMaterialUtility.SetShaderNonModifiableDefaults(
            shader,
            configuredTextures.Where(x => !x.modifiable).Select(x => x.name).ToArray(),
            configuredTextures.Where(x => !x.modifiable).Select(x => EditorUtility.InstanceIDToObject(x.textureId) as Texture).ToArray());

        ctx.AddObjectToAsset("MainAsset", shader);
        ctx.SetMainObject(shader);
    }

    internal static string GetShaderText(string path, out List<PropertyCollector.TextureInfo> configuredTextures)
    {
        string shaderString = null;
        var shaderName = Path.GetFileNameWithoutExtension(path);
        try
        {
            var textGraph = File.ReadAllText(path, Encoding.UTF8);
            var graph = JsonUtility.FromJson<MaterialGraph>(textGraph);
            graph.LoadedFromDisk();

            if (!string.IsNullOrEmpty(graph.path))
                shaderName = graph.path + "/" + shaderName;
            shaderString = graph.GetShader(shaderName, GenerationMode.ForReals, out configuredTextures);
        }
        catch (Exception)
        {
            // ignored
        }
        configuredTextures = new List<PropertyCollector.TextureInfo>();
        return shaderString ?? k_ErrorShader.Replace("Hidden/GraphErrorShader2", shaderName);
    }
}

class ShaderGraphAssetPostProcessor : AssetPostprocessor
{
    static void RegisterShaders(string[] paths)
    {
        foreach (var path in paths)
        {
            if (!path.EndsWith(ShaderGraphImporter.ShaderGraphExtension, StringComparison.InvariantCultureIgnoreCase))
                continue;

            var mainObj = AssetDatabase.LoadMainAssetAtPath(path);
            if (mainObj is Shader)
                ShaderUtil.RegisterShader((Shader)mainObj);

            var objs = AssetDatabase.LoadAllAssetRepresentationsAtPath(path);
            foreach (var obj in objs)
            {
                if (obj is Shader)
                    ShaderUtil.RegisterShader((Shader)obj);
            }
        }
    }

    static void OnPostprocessAllAssets(string[] importedAssets, string[] deletedAssets, string[] movedAssets, string[] movedFromAssetPaths)
    {
        MaterialGraphEditWindow[] windows = Resources.FindObjectsOfTypeAll<MaterialGraphEditWindow>();
        foreach (var matGraphEditWindow in windows)
        {
            matGraphEditWindow.forceRedrawPreviews = true;
        }
        RegisterShaders(importedAssets);
    }
}