Workaround for EDT error message when reopening a project (#1424)

CHANGELOG.adoc

@@ -11,6 +11,7 @@ This document provides a high-level view of the changes introduced by release.
 
 - Fix class cast exception when parsing Antora information (#1422)
 - Fix regex problem when `idseparator` contains regex special characters (#1423)
+- Workaround for EDT error message when reopening a project (#1424)
 
 === 0.39.3
 

src/main/java/org/asciidoc/intellij/ui/SplitTextEditorProvider.java

@@ -1,5 +1,6 @@
 package org.asciidoc.intellij.ui;
 
+import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.openapi.fileEditor.AsyncFileEditorProvider;
 import com.intellij.openapi.fileEditor.FileEditor;
 import com.intellij.openapi.fileEditor.FileEditorPolicy;
@@ -12,6 +13,8 @@
 import org.jdom.Element;
 import org.jetbrains.annotations.NotNull;
 
+import java.util.concurrent.atomic.AtomicReference;
+
 public abstract class SplitTextEditorProvider implements AsyncFileEditorProvider, DumbAware {
 
   private static final String FIRST_EDITOR = "first_editor";
@@ -58,8 +61,19 @@ public Builder createEditorAsync(@NotNull final Project project, @NotNull final
 
     return new Builder() {
       @Override
-      public FileEditor build() {
-        return createSplitEditor(firstBuilder.build(), secondBuilder.build());
+      public @NotNull FileEditor build() {
+        if (!ApplicationManager.getApplication().isDispatchThread()) {
+          // FileEditorManagerImpl$dumbModeFinished$fileToNewProviders will call this in a background thread
+          // EditorImpl wants to be called from EDT only, let's switch to EDT for this.
+          // This is a known problem: https://youtrack.jetbrains.com/issue/IDEA-318259 in 2023.2 and will be fixed in 2023.3
+          AtomicReference<FileEditor> editor = new AtomicReference<>();
+          ApplicationManager.getApplication().invokeAndWait(() -> {
+            editor.set(createSplitEditor(firstBuilder.build(), secondBuilder.build()));
+          });
+          return editor.get();
+        } else {
+          return createSplitEditor(firstBuilder.build(), secondBuilder.build());
+        }
       }
     };
   }