EditorApplication.isCompiling  

static var isCompiling : boolean

Description

Is editor currently compiling scripts? (Read Only)

Editor Window that tells you if Unity is compiling scripts.

// Dont let the user enter in play mode if the editor is compiling the assemblies

class FinishCompiling extends EditorWindow {

    @MenuItem("Example/Dont Let Play until finish compiling")
    static function Init() {
        var window : FinishCompiling = 
            EditorWindow.GetWindowWithRect(FinishCompiling, Rect(0,0,165,40));
        window.Show();    
    }
    function OnGUI () {
        EditorGUILayout.LabelField("Compiling:", EditorApplication.isCompiling?"YES" : "No");
    }
    function Update() {
        if(EditorApplication.isCompiling) {
            EditorApplication.isPlaying = false;
        }
    }
}