fix more lint

Author: Feiyang1

config/.eslintrc.js

@@ -146,7 +146,9 @@ module.exports = {
           'String': "Use 'string' instead.",
           'Number': "Use 'number' instead.",
           'Boolean': "Use 'boolean' instead.",
-          'Function': 'Avoid the Function type, as it provides little safety'
+          'Function': `Avoid the Function type, as it provides little safety for the following reasons:
+                       It provides no type safety when calling the value, which means it's easy to provide the wrong arguments.
+                       It accepts class declarations, which will fail when called, as they are called without the new keyword.`
         },
         'extendDefaults': false
       }

packages/database/src/core/util/util.ts

@@ -428,7 +428,7 @@ export function each(obj: object, fn: (k: string, v: unknown) => void) {
 export const bindCallback = function (
   callback: (a: unknown) => void,
   context?: object | null
-): Function {
+): (a: unknown) => void {
   return context ? callback.bind(context) : callback;
 };
 
@@ -609,6 +609,7 @@ export const exceptionGuard = function (fn: () => void) {
  * @param {...*} varArgs Arbitrary args to be passed to opt_onComplete
  */
 export const callUserCallback = function (
+  // eslint-disable-next-line @typescript-eslint/ban-types
   callback?: Function | null,
   ...varArgs: unknown[]
 ) {
@@ -665,7 +666,7 @@ export const exportPropGetter = function (
  * @return {number|Object} The setTimeout() return value.
  */
 export const setTimeoutNonBlocking = function (
-  fn: Function,
+  fn: () => void,
   time: number
 ): number | object {
   const timeout: number | object = setTimeout(fn, time);

packages/database/test/helpers/EventAccumulator.ts

@@ -37,6 +37,7 @@ export class EventAccumulator {
   reject;
   private onResetFxn;
   private onEventFxn;
+  // eslint-disable-next-line @typescript-eslint/ban-types
   constructor(public condition: Function) {
     this.promise = new Promise((resolve, reject) => {
       this.resolve = resolve;
@@ -52,6 +53,7 @@ export class EventAccumulator {
       this.resolve(this.eventData);
     }
   }
+  // eslint-disable-next-line @typescript-eslint/ban-types
   reset(condition?: Function) {
     this.eventData = [];
     this.promise = new Promise((resolve, reject) => {
@@ -65,9 +67,11 @@ export class EventAccumulator {
       this.condition = condition;
     }
   }
+  // eslint-disable-next-line @typescript-eslint/ban-types
   onEvent(cb: Function) {
     this.onEventFxn = cb;
   }
+  // eslint-disable-next-line @typescript-eslint/ban-types
   onReset(cb: Function) {
     this.onResetFxn = cb;
   }

packages/firestore/test/util/equality_matcher.ts

@@ -32,6 +32,7 @@ export interface Equatable<T> {
  */
 export interface CustomMatcher<T> {
   equalsFn: (left: T, right: T) => boolean;
+  // eslint-disable-next-line @typescript-eslint/ban-types
   forType: Function;
 }