Domain Reload View

The Domain Reload View displays the results of a Roslyn analyzer that detects code issues that would result in surprising or non-deterministic behavior if domain reload is disabled in your project. Since domain reloading can impact project iteration times (in particular, the time it takes to enter and exit Play Mode), it's usually a very good idea to fix all of the issues shown in this View and then to disable domain reload.

In order for the Domain Reload View to show data, you need to allow Project Auditor to run Roslyn analyzers when analyzing your project's code. The use of Roslyn analyzers can cause Project Auditor's analysis to take longer, so it is disabled by default. To allow Project Auditor to use Roslyn analyzers, make sure the corresponding option is enabled in Preferences > Analysis > Project Auditor > Use Roslyn Analyzers. To open the Preferences window, go to Edit > Preferences (macOS: Unity > Settings) in the main menu.

To disable Domain Reloading:

1. Go to Edit > Project Settings > Editor
2. Make sure Enter Play Mode Options is enabled.
3. Disable Reload Domain

What is Domain Reload?

Domain Reloading resets the scripting state of the engine, resetting any static variables or events. By default, this is automatically triggered when entering Play Mode, ensuring that the project will be in a completely fresh state, as it would be when initially launched in a build. However, this comes with some performance impact, which is amplified by a project's complexity, and also any additional behaviour that is hooked on to the Domain Reload (e.g. the contents of functions with the InitializeOnLoad attribute in ScriptableObjects). The cumulative effect of this can cause a significant increase in Editor iteration time, and by extension have an impact on your team's productivity.

To get around this, the Unity Editor provides the option to disable Domain Reloading. This will ensure that entering Play Mode will always be quick. However, if not correctly reinitialised, static variables and events will retain their values, potentially causing undesirable behaviour. This can be addressed by the addition of an initialisation function with the RuntimeInitialiseOnLoadMethod attribute. Methods with this attribute will be called when Play Mode is entered even if Domain Reloading is disabled, allowing you to ensure that static variables or events are initialised correctly.

For information on why you may wish to disable Domain Reloading, and what needs to be done to do so safely, see the relevant documentation here: https://docs.unity3d.com/Manual/DomainReloading.html

What does the Domain Reload Analyzer do?

This analyzer searches for the declaration of any static variables or events in a project. If they are found, it then checks for the presence of a method with the RuntimeInitializeOnLoadMethod attribute. If such a method exists, its contents are analyzed to determine if the static variable or event is assigned to within its scope.

Warning diagnostics are raised by the analyzer if:

• No method with the RuntimeInitializeOnLoadMethod attribute exists
• A variable being analyzed is not explicitly assigned within the initialize method
• An event being analyzed is not explicitly unsubscribed from within the initialize method

How do I resolve these Issues?

To resolve the Issues reported in a C# script, you must do the following:

• Create an initialization function with the RuntimeInitializeOnLoadMethod attribute
• For every static variable in the script, ensure that it is assigned a value within the scope of the initialization function
• For every static event in the script, ensure that any functions that subscribe to the event are unsubscribed

The View table

The table columns are as follows:

Column Name	Column Description
Code	The error/warning code reported by the compiler.
Issue	The error/warning message string reported by the compiler. Click on an Issue to see more details in the panel on the right.
Filename	The file name and line number that generated the message. Double-click on any report item to automatically open the file in your IDE and jump to the correct line.
Assembly	The assembly which contains the file that generated the message. The default assembly for user code in a Unity project is called Assembly-CSharp.