Added pre and post compiler callbacks for compiling UdonSharpProgramAsset

This pull request adds support for beforeProgramAssetCompile and afterProgramAssetCompile callbacks to UdonSharpCompiler which allows for additional pre/post pipelining steps such as method stub generation, source file overrides, cache updates, etc when an UdonSharpProgramAsset is to be compiled by UdonSharp.

An example use case:

using System;
using UdonSharp;
using UnityEngine;
using VRC.SDKBase;
using VRC.Udon;

public class MyUdonSharpBehaviour : UdonSharpBehaviour {
    public void OnCustomEvent(string eventName) {
        Debug.Log(eventName);
    }

    // Custom event stubs in this section are automatically generated before compile time and will be overwritten.
    /*<#UDONSHARP_CUSTOMEVENTS#>*/
    // These methods would be listed in the source file after compilation has completed.  Alternative implementations could temporarily override the original source file during compilation.
    /*public void MyFirstCustomEvent() {
        OnCustomEvent("MyFirstCustomEvent");
    }
    public void MySecondCustomEvent() {
        OnCustomEvent("MySecondCustomEvent");
    }
    public void MyThirdCustomEvent() {
        OnCustomEvent("MyThirdCustomEvent");
    }*/
    /*<#!UDONSHARP_CUSTOMEVENTS!#>*/
}

#if !COMPILER_UDONSHARP && UNITY_EDITOR
using UdonSharpEditor;
using UnityEditor;
using System.IO;
using System.Collections;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using System.Linq;

[CustomEditor(typeof(MyUdonSharpBehaviour))]
public class MyUdonSharpBehaviourInspectorEditor : Editor {
    public override void OnInspectorGUI() {
        UdonSharpCustomEventUtil.CustomEventNames.Add("MyFirstCustomEvent");
        UdonSharpCustomEventUtil.CustomEventNames.Add("MySecondCustomEvent");
        UdonSharpCustomEventUtil.CustomEventNames.Add("MyThirdCustomEvent");
    }
}

[InitializeOnLoad]
public static class UdonSharpCustomEventUtil {
    public static readonly string CustomEventStubMarker = "/*<#UDONSHARP_CUSTOMEVENTS#>*/";
    public static readonly string CustomEventStubMarkerEnd = "/*<#!UDONSHARP_CUSTOMEVENTS!#>*/";
    public static readonly string CustomEventStubMethodName = "OnCustomEvent";

    private static HashSet<string> CustomEventNames = new HashSet<string>();

    static UdonSharpCustomEventUtil() {
        UdonSharpCompiler.beforeProgramAssetCompile += OnUdonSharpCompile;
    }

    private static void OnUdonSharpCompile(UdonSharpProgramAsset programAsset) {
        var program = UdonSharpEditorUtility.GetUdonSharpProgramAsset(typeof(MyUdonSharpBehaviour));
        if(programAsset != null && programAsset.sourceCsScript != null && programAsset == program) BuildCustomEvents();
    }

    private static void BuildCustomEvents() {
        var orderedEventNames = CustomEventNames.OrderBy(x => x).ToList();

        // Generate stub code
        var customEventStubs = CustomEventStubMarker;
        foreach(var eventName in orderedEventNames) customEventStubs += BuildCustomEventMethodStub(eventName, CustomEventStubMethodName);
        customEventStubs += "\n\t" + CustomEventStubMarkerEnd;

        var program = UdonSharpEditorUtility.GetUdonSharpProgramAsset(typeof(MyUdonSharpBehaviour));
        var sourceFileName = AssetDatabase.GetAssetPath(program.sourceCsScript);
        var sourceCode = File.ReadAllText(sourceFileName);

        var expression = String.Format("{0}(.*){1}", Regex.Escape(CustomEventStubMarker), Regex.Escape(CustomEventStubMarkerEnd));
        var newSourceCode = Regex.Replace(sourceCode, expression, customEventStubs, RegexOptions.Singleline);
        if(newSourceCode != sourceCode) File.WriteAllText(sourceFileName, newSourceCode);
    }

    private static string BuildCustomEventMethodStub(string eventName, string methodName) {
        return "\n\tpublic void " + eventName + "() {\n\t\t" + methodName + "(\"" + eventName + "\");\n\t}";
    }
}
#endif

MerlinVR / UdonSharp

Added pre and post compiler callbacks for compiling UdonSharpProgramAsset #64