[VIM-3541] Prevent entering insert mode in read-only files

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

@@ -11,6 +11,8 @@ package org.jetbrains.plugins.ideavim.action.change.insert
 import com.maddyhome.idea.vim.state.mode.Mode
 import org.jetbrains.plugins.ideavim.VimTestCase
 import org.junit.jupiter.api.Test
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.ValueSource
 
 class InsertExitModeActionTest : VimTestCase() {
   @Test
@@ -22,4 +24,73 @@ class InsertExitModeActionTest : VimTestCase() {
   fun `test exit visual mode on line start`() {
     doTest("i<Esc>", "${c}123", "${c}123", Mode.NORMAL())
   }
+
+  @ParameterizedTest
+  @ValueSource(strings = ["i", "a", "o", "O"])
+  fun `test read-only file allows insert entry but blocks changes`(insertCommand: String) {
+    configureByText("12${c}3")
+    fixture.editor.document.setReadOnly(true)
+
+    // Enter insert-like commands, then immediately escape; no text should change and ESC should work
+    typeText("$insertCommand<Esc>")
+
+    assertMode(Mode.NORMAL())
+    assertState("12${c}3")
+  }
+
+  @Test
+  fun `test cannot change text in read-only file with c motion`() {
+    configureByText("12${c}3")
+    fixture.editor.document.setReadOnly(true)
+
+    // Try to change with 'cw' - should prevent the change
+    typeText("cw")
+
+    // Should remain in normal mode
+    assertMode(Mode.NORMAL())
+    assertState("12${c}3")
+  }
+
+  @Test
+  fun `test cannot change text in read-only file with r motion`() {
+    configureByText("12${c}3")
+    fixture.editor.document.setReadOnly(true)
+
+    // Try to change with 'r' - should prevent the change
+    typeText("rX")
+
+    // Should remain in normal mode
+    assertMode(Mode.NORMAL())
+    assertState("12${c}3")
+
+  }
+
+  @Test
+  fun `test exit insert mode in read-only file`() {
+    // Test that ESC works in read-only files without hanging
+    configureByText("test ${c}content")
+    fixture.editor.document.setReadOnly(true)
+
+    // This should complete without hanging or errors
+    typeText("i<Esc>")
+
+    // Reset read-only status
+    fixture.editor.document.setReadOnly(false)
+  }
+
+  @Test
+  fun `test exit insert mode with repeat count in read-only file`() {
+    // Test that ESC works with repeat counts in read-only files
+    configureByText("${c}hello")
+    fixture.editor.document.setReadOnly(true)
+
+    // 3i should repeat the insert 3 times when ESC is pressed
+    // In read-only files, this should exit cleanly without hanging
+    typeText("3i<Esc>")
+    assertMode(Mode.NORMAL())
+    assertState("${c}hello")
+
+    // Reset read-only status
+    fixture.editor.document.setReadOnly(false)
+  }
 }

vim-engine/src/main/kotlin/com/maddyhome/idea/vim/action/change/insert/InsertExitModeAction.kt

@@ -11,16 +11,18 @@ import com.intellij.vim.annotations.CommandOrMotion
 import com.intellij.vim.annotations.Mode
 import com.maddyhome.idea.vim.api.ExecutionContext
 import com.maddyhome.idea.vim.api.VimEditor
+import com.maddyhome.idea.vim.api.injector
 import com.maddyhome.idea.vim.command.Command
 import com.maddyhome.idea.vim.command.OperatorArguments
 import com.maddyhome.idea.vim.handler.VimActionHandler
+import com.maddyhome.idea.vim.api.VimMarkService
+import com.maddyhome.idea.vim.mark.VimMarkConstants.MARK_CHANGE_END
+import com.maddyhome.idea.vim.state.mode.Mode as VimMode
 
 @CommandOrMotion(keys = ["<C-[>", "<C-C>", "<Esc>"], modes = [Mode.INSERT])
 class InsertExitModeAction : VimActionHandler.SingleExecution() {
-  // Note that hitting Escape can insert text when exiting insert mode after visual block mode.
-  // If the editor is read-only, we'll get a "This view is read-only" tooltip. However, we should only enter insert
-  // mode if both editor and document are writable.
-  override val type: Command.Type = Command.Type.INSERT
+  // Note: ESC should not require write access itself; any write is gated in processEscape.
+  override val type: Command.Type = Command.Type.OTHER_SELF_SYNCHRONIZED
 
   override fun execute(
     editor: VimEditor,

vim-engine/src/main/kotlin/com/maddyhome/idea/vim/action/change/insert/InsertNewLineBelowAction.kt

@@ -107,6 +107,7 @@ private fun insertNewLineAbove(editor: VimEditor, context: ExecutionContext) {
  */
 private fun insertNewLineBelow(editor: VimEditor, context: ExecutionContext) {
   if (editor.isOneLineMode()) return
+
   for (caret in editor.nativeCarets()) {
     caret.moveToOffset(injector.motion.moveCaretToCurrentLineEnd(editor, caret))
   }

vim-engine/src/main/kotlin/com/maddyhome/idea/vim/api/VimChangeGroupBase.kt

@@ -404,6 +404,13 @@ abstract class VimChangeGroupBase : VimChangeGroup {
    * @param context The data context
    */
   override fun insertAfterCaret(editor: VimEditor, context: ExecutionContext) {
+    // Prevent entering insert mode in read-only files before moving the caret
+    if (!editor.isWritable()) {
+      injector.messages.showStatusBarMessage(editor, "Cannot make changes, file is read-only")
+      injector.messages.indicateError()
+      return
+    }
+
     for (caret in editor.nativeCarets()) {
       caret.moveToMotion(injector.motion.getHorizontalMotion(editor, caret, 1, true))
     }
@@ -441,6 +448,13 @@ abstract class VimChangeGroupBase : VimChangeGroup {
    * @param mode    The mode - indicate insert or replace
    */
   override fun initInsert(editor: VimEditor, context: ExecutionContext, mode: Mode) {
+    // Prevent entering insert mode in read-only files
+    if (!editor.isWritable()) {
+      injector.messages.showStatusBarMessage(editor, "Cannot make changes, file is read-only")
+      injector.messages.indicateError()
+      return
+    }
+
     val state = injector.vimState
     injector.application.runReadAction {
       for (caret in editor.nativeCarets()) {