Is there any way to hide script fields outside of prefab that uses it?

Questions & Answers
1

Script fields (marked with [SerializeField] attribute) is popular way to setup script dependecies. Other alternative - using FindComponents or FindObject - look less controlable.
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Main drawbacks of [SerializeField] setup is flooding script GUI inspector with internal prefab dependices.
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For example, I have Car prefab with CarControlComponent script, that needs referencies to four car wheels. This script may contain some fields that are usable for prefab setup (like Max/Min speed, Rotation speed, et.c.) and that fields should be accassable by prefab user - but wheel references are constructed for in-prefab needs only and should be “incapsulated”.
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So, the question: is there any way to hide script inspector fields outside of prefab if script is used in prefab object?

2

If I understand you correctly, you want to show some serialized fields only if you are in prefab mode (>= Unity 2018.3)?

If so, you can achieve this using an attribute and a property drawer:

// PrefabModeOnlyAttribute.cs, located in your script files
public class PrefabModeOnlyAttribute : UnityEngine.PropertyAttribute { }

//PrefabModeOnlyDrawer.cs, located in an Editor folder

using UnityEngine;
using UnityEditor;
using UnityEditor.Experimental.SceneManagement;

[CustomPropertyDrawer( typeof( PrefabModeOnly ) )]
public class PrefabModeOnlyDrawer : PropertyDrawer
{
    public override float GetPropertyHeight( SerializedProperty property, GUIContent label )
    {
        return ( PrefabStageUtility.GetCurrentPrefabStage() == null ) ? 0 : EditorGUI.GetPropertyHeight( property, label );
    }
    public override void OnGUI( Rect position, SerializedProperty property, GUIContent label )
    {
        if ( PrefabStageUtility.GetCurrentPrefabStage() == null ) return;
        EditorGUI.PropertyField( position, property, label );
    }
}

Then, in your CarControlComponent script:

[SerializeField, PrefabModeOnly]
private GameObject[] wheels;
3

@Hellium A good start, however this makes the fields visible in other Prefabs as well.
Also there is no support for hiding fields that only make sense outside of the Prefab. (Like: a specific Sprite, Manager, Handler, System, Position, Unique name…)

My solution would be:

PrefabOnlyAttribute.cs:

public class PrefabOnlyAttribute : PropertyAttribute { }
public class InstanceOnlyAttribute : PropertyAttribute { }

Editor/PrefabOnlyDrawer.cs:

[CustomPropertyDrawer(typeof(PrefabOnlyAttribute))]
public class PrefabOnlyDrawer : PropertyDrawer
{
	public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
	{
		return property.isInstantiatedPrefab ? 0 : EditorGUI.GetPropertyHeight(property, label);
	}
	public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
	{
		if (property.isInstantiatedPrefab) return;
		EditorGUI.PropertyField(position, property, label);
	}
}

[CustomPropertyDrawer(typeof(InstanceOnlyAttribute))]
public class InstanceOnlyDrawer : PropertyDrawer
{
	public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
	{
		return !property.isInstantiatedPrefab ? 0 : EditorGUI.GetPropertyHeight(property, label);
	}
	public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
	{
		if (!property.isInstantiatedPrefab) return;
		EditorGUI.PropertyField(position, property, label);
	}
}

MyCode.cs:

  // Only needed when editing THIS prefab.
  [SerializeField, PrefabOnly] private GameObject[] wheels;

  // Always overwritten, never needed when editing THIS prefab.
  [SerializeField, InstanceOnly] private string driverName;

Again, thanks to @Hellium for setting me on the right path!