VIM-4084 Ensure insert mode respects file's writable state

src/main/java/com/maddyhome/idea/vim/newapi/IjVimEditor.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2003-2023 The IdeaVim authors
+ * Copyright 2003-2026 The IdeaVim authors
  *
  * Use of this source code is governed by an MIT-style
  * license that can be found in the LICENSE.txt file or at
@@ -77,7 +77,6 @@ internal class IjVimEditor(editor: Editor) : MutableLinearEditor, VimEditorBase(
   // Be careful: all the EditorActionHandler implementation should correctly process InjectedEditors
   // TBH, I don't like the names. Need to think a bit more about this
   val editor = editor.getTopLevelEditor()
-  val originalEditor = editor
   override var replaceMask: VimEditorReplaceMask?
     get() = editor.replaceMask
     set(value) {
@@ -150,6 +149,7 @@ internal class IjVimEditor(editor: Editor) : MutableLinearEditor, VimEditorBase(
         }
       }
     }
+    if (!isWritable()) return
     editor.document.insertString(atPosition, text)
   }
 

src/test/java/org/jetbrains/plugins/ideavim/action/change/insert/InsertExitModeActionTest.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2003-2023 The IdeaVim authors
+ * Copyright 2003-2026 The IdeaVim authors
  *
  * Use of this source code is governed by an MIT-style
  * license that can be found in the LICENSE.txt file or at
@@ -38,6 +38,20 @@ class InsertExitModeActionTest : VimTestCase() {
     assertState("12${c}3")
   }
 
+  @Test
+  fun `esc with insert should check if file is writable`() {
+    configureByText("12${c}3")
+    typeText("10i1")
+    fixture.editor.document.setReadOnly(true)
+
+    // escape trigger write 1 10 times
+    typeText("<Esc>")
+
+    // Should remain in normal mode
+    assertMode(Mode.NORMAL())
+    assertState("121${c}3")
+  }
+
   @Test
   fun `test cannot change text in read-only file with c motion`() {
     configureByText("12${c}3")