how to get a callback when build was canceled?

Questions & Answers
1

I am using unity 2019.2 with Android.
When the build succeeds, OnPostprocessBuild(BuildReport report) gets called, but not if it is canceled.
Is it supposed to? Are there other means?

public class PostProcessor : IPostprocessBuildWithReport
{
	public int callbackOrder => 0;
	
	public void OnPostprocessBuild(BuildReport report)
	{
		//do some stuff
    
		if (report.summary.result != BuildResult.Succeeded) { return; }

		#region Platform-specific configurations

		switch (report.summary.platform)
		{
				//do some stuff
		}
		#endregion
	}
}
2

Use this BuildHandler class:

using System;
using UnityEditor;
using UnityEngine;

/// <summary>
/// Handler for Builds.
/// <para>
/// Use <see cref="OnBuildStarted"/> and/or <see cref="OnBuildCleanup"/>
/// to execute code during the build process.
/// </para>
/// <para>Class created using https://stackoverflow.com/a/68650717</para>
/// </summary>
[InitializeOnLoad]
public class BuildHandler
{
    /// <summary>
    /// Action fired when the build process starts.
    /// </summary>
    public static event Action OnBuildStarted;

    /// <summary>
    /// Action fired when the build process ends, even though the build is canceled.
    /// </summary>
    public static event Action OnBuildCleanup;

    static BuildHandler () => BuildPlayerWindow.RegisterBuildPlayerHandler(HandleBuildPlayer);

    static void HandleBuildPlayer (BuildPlayerOptions buildOptions)
    {
        try
        {
            OnBuildStarted?.Invoke();
            // Start Unity's default building process.
            BuildPlayerWindow.DefaultBuildMethods.BuildPlayer(buildOptions);
        }
        catch (Exception ex)
        {
            Exception log = ex.InnerException ?? ex;
            Debug.LogException(log);
            Debug.LogErrorFormat("{0} in BuildHandler: '{1}'", log.GetType().Name, ex.Message);
        }
        finally
        {
            OnBuildCleanup?.Invoke();
        }
    }
}

Now you have to use the actions OnBuildStarted or OnBuildCleanup.

Here is an example:

using UnityEditor;
using UnityEngine;

[InitializeOnLoad]
public class SomeBuildProcess
{
    static SomeBuildProcess ()
    {
        BuildHandler.OnBuildStarted += HandleBuildStarted;
        BuildHandler.OnBuildCleanup += HandleBuildCleanup;
    }

    ~SomeBuildProcess ()
    {
        BuildHandler.OnBuildStarted -= HandleBuildStarted;
        BuildHandler.OnBuildCleanup -= HandleBuildStarted;
    }

    static void HandleBuildStarted ()
    {
        Debug.Log("HandleBuildStarted");
    }

    static void HandleBuildCleanup ()
    {
        Debug.Log("HandleBuildCleanup");
    }   
}

Credits for the BuildHandler class: Unity Editor detect when build fails - Stack Overflow