Remove the optimization and detect if mightChangeDocument is miscon…

…figured

src/history/historyTracker.ts

@@ -425,12 +425,14 @@ export class HistoryTracker {
    *
    * Determines what changed by diffing the document against what it
    * used to look like.
+   *
+   * @returns true if a change was added
    */
-  public addChange(cursorPosition = [new Position(0, 0)]): void {
+  public addChange(cursorPosition = [new Position(0, 0)]): boolean {
     const newText = this._getDocumentText();
 
     if (newText === this.oldText) {
-      return;
+      return false;
     }
 
     // Determine if we should add a new Step.
@@ -495,6 +497,8 @@ export class HistoryTracker {
 
     // A change has been made, reset the changelist navigation index to the end
     this.changelistIndex = this.historySteps.length - 1;
+
+    return true;
   }
 
   /**

src/mode/modeHandler.ts

@@ -602,8 +602,25 @@ export class ModeHandler implements vscode.Disposable {
       if (this.vimState.alteredHistory) {
         this.vimState.alteredHistory = false;
         vimState.historyTracker.ignoreChange();
-      } else if (action.mightChangeDocument) {
-        vimState.historyTracker.addChange(this.vimState.cursorsInitialState.map(c => c.stop));
+      } else {
+        const addedChange = vimState.historyTracker.addChange(
+          this.vimState.cursorsInitialState.map(c => c.stop)
+        );
+        if (addedChange && !action.mightChangeDocument) {
+          const errorMsg = `Action '${action.toString()}' changed the document unexpectedly`;
+          const choice = await vscode.window.showErrorMessage(
+            `${errorMsg}! This is a bug - please report it.`,
+            'Report bug'
+          );
+          if (choice === 'Report bug') {
+            vscode.commands.executeCommand(
+              'vscode.open',
+              vscode.Uri.parse(
+                `https://github.com/VSCodeVim/Vim/issues/new?title=${errorMsg}&labels=bug`
+              )
+            );
+          }
+        }
       }
     }