clear history when content from disk is changed

extension.ts

@@ -8,6 +8,7 @@
 
 import * as vscode from 'vscode';
 import * as util from './src/util';
+import * as _ from "lodash";
 import { showCmdLine } from './src/cmd_line/main';
 import { ModeHandler } from './src/mode/modeHandler';
 import { TaskQueue } from './src/taskQueue';
@@ -114,6 +115,15 @@ export async function activate(context: vscode.ExtensionContext) {
 
   vscode.window.onDidChangeActiveTextEditor(handleActiveEditorChange, this);
 
+  vscode.workspace.onDidChangeTextDocument((event) => {
+    /* TODO: Remove setTimeout (https://github.com/Microsoft/vscode/issues/11339) */
+    setTimeout(() => {
+      if (event.document.isDirty === false) {
+        handleContentChangedFromDisk(event.document);
+      }
+    }, 0);
+  });
+
   registerCommand(context, 'type', async (args) => {
     if (!vscode.window.activeTextEditor) {
       return;
@@ -217,6 +227,13 @@ async function handleKeyEvent(key: string): Promise<void> {
   });
 }
 
+function handleContentChangedFromDisk(document : vscode.TextDocument) : void {
+  _.filter(modeHandlerToEditorIdentity, { "fileName" : document.fileName})
+    .forEach((modeHandler) => {
+      modeHandler.vimState.historyTracker.clear();
+    });
+}
+
 async function handleActiveEditorChange(): Promise<void> {
 
   // Don't run this event handler during testing

src/history/historyTracker.ts

@@ -177,6 +177,16 @@ export class HistoryTracker {
   }
 
   constructor() {
+    this._initialize();
+  }
+
+  public clear() {
+    this.historySteps = [];
+    this.currentHistoryStepIndex = 0;
+    this._initialize();
+  }
+
+  private _initialize() {
     /**
      * We add an initial, unrevertable step, which inserts the entire document.
      */

src/mode/modeHandler.ts

@@ -458,7 +458,7 @@ export class ModeHandler implements vscode.Disposable {
   /**
    * Filename associated with this ModeHandler. Only used for debugging.
    */
-  public filename: string;
+  public fileName: string;
 
   private _caretDecoration = vscode.window.createTextEditorDecorationType(
   {
@@ -491,7 +491,7 @@ export class ModeHandler implements vscode.Disposable {
   constructor(filename = "") {
     ModeHandler.IsTesting = Globals.isTesting;
 
-    this.filename = filename;
+    this.fileName = filename;
 
     this._vimState = new VimState();
     this._insertModeRemapper = new InsertModeRemapper(true);
@@ -532,7 +532,7 @@ export class ModeHandler implements vscode.Disposable {
         return;
       }
 
-      if (e.textEditor.document.fileName !== this.filename) {
+      if (e.textEditor.document.fileName !== this.fileName) {
         return;
       }