Enable noImplicitThis setting of TypeScript

[ravicious]

https://www.typescriptlang.org/tsconfig#noImplicitThis

I feel we should enable this setting because writing code with implicit this makes it impossible for the TypeScript language server to find references for code which uses implicit this. See the example with this.clear() below.

With this setting enabled, I'm getting the following number of errors on master (cfc3480):

Errors  Files
    27  web/packages/shared/utils/highbar.ts:111
     2  web/packages/teleport/src/services/websession/websession.ts:156

Implicit this of an object

teleport/web/packages/teleport/src/services/websession/websession.ts

Lines 35 to 48 in cfc3480

	const session = {
	logout(rememberLocation = false) {
	api.delete(cfg.api.webSessionPath).finally(() => {
	history.goToLogin(rememberLocation);
	});
	this.clear();
	},
	clear() {
	this._stopTokenChecker();
	localStorage.unsubscribe(receiveMessage);
	localStorage.clear();
	},

On the line with this.clear(), this is of type any. As such, if you want to find references to the clear function, this callsite won't be listed there. The solution to this is to replace this with session. In Connect, we did so for a long time since routing in uri.ts uses a similar pattern:

teleport/web/packages/teleterm/src/ui/uri.ts

Lines 95 to 100 in cfc3480

	export const routing = {
	parseClusterUri(uri: string) {
	const leafMatch = routing.parseUri(uri, paths.leafCluster);
	const rootMatch = routing.parseUri(uri, paths.rootCluster);
	return leafMatch || rootMatch;
	},

Implicit this inside a function

This happens mostly in highbar.ts and it's exactly what the docs of noImplicitThis describe. It can be solved by using an arrow function.

diff --git a/web/packages/shared/utils/highbar.ts b/web/packages/shared/utils/highbar.ts
index fda5f461a9..63bd24a5b6 100644
--- a/web/packages/shared/utils/highbar.ts
+++ b/web/packages/shared/utils/highbar.ts
@@ -103,19 +103,19 @@ export function isObject(checkVal: unknown): boolean {
  * Based on Underscore.js 1.8.3 <http://underscorejs.org/LICENSE>
  * Copyright Jeremy Ashkenas, DocumentCloud and Investigative Reporters & Editors
  */
-export function runOnce<T extends (...args) => any>(func: T) {
+export const runOnce = <T extends (...args) => any>(func: T) => {
   let n = 2;
   let result;
-  return function () {
+  return (...args) => {
     if (--n > 0) {
-      result = func.apply(this, arguments);
+      result = func.apply(this, ...args);
     }
     if (n <= 1) {
       func = undefined;
     }
     return result;
   };
-}
+};
 
 interface ThrottleSettings {
   leading?: boolean | undefined;