Fix linting issues (#22062)

Summary:
Fixes lots of ESLint warnings. Many of them where in PR #20877 by janicduplessis which requested to split the linting fixes from configuration and package changes.

I solved only the issues that I was most certain about but I would love to get hands on all of them with a little bit of input.
Pull Request resolved: facebook/react-native#22062

Differential Revision: D12889447

Pulled By: TheSavior

fbshipit-source-id: 35f7a08104a5b859c860afdde4af2b32c0685c50

generator/promptSync.js

@@ -19,11 +19,7 @@ function create() {
   return prompt;
 
   function prompt(ask, value, opts) {
-    var insert = 0,
-      savedinsert = 0,
-      res,
-      i,
-      savedstr;
+    var insert = 0;
     opts = opts || {};
 
     if (Object(ask) === ask) {
@@ -52,15 +48,10 @@ function create() {
       character,
       read;
 
-    savedstr = '';
-
     if (ask) {
       process.stdout.write(ask);
     }
 
-    var cycle = 0;
-    var prevComplete;
-
     while (true) {
       read = fs.readSync(fd, buf, 0, 3);
       if (read > 1) {
@@ -80,7 +71,7 @@ function create() {
       character = buf[read - 1];
 
       // catch a ^C and return null
-      if (character == 3) {
+      if (character === 3) {
         process.stdout.write('^C\n');
         fs.closeSync(fd);
         process.exit(130);
@@ -89,12 +80,15 @@ function create() {
       }
 
       // catch the terminating character
-      if (character == term) {
+      if (character === term) {
         fs.closeSync(fd);
         break;
       }
 
-      if (character == 127 || (process.platform == 'win32' && character == 8)) {
+      if (
+        character === 127 ||
+        (process.platform === 'win32' && character === 8)
+      ) {
         //backspace
         if (!insert) {
           continue;
@@ -119,7 +113,7 @@ function create() {
         );
       } else {
         process.stdout.write('\u001b[s');
-        if (insert == str.length) {
+        if (insert === str.length) {
           process.stdout.write('\u001b[2K\u001b[0G' + ask + str);
         } else {
           if (ask) {

link/__tests__/ios/writePlist.spec.js

@@ -49,7 +49,7 @@ describe('ios::writePlist', () => {
 
   it('should write a `.plist` file', () => {
     plistPath = '/Basic/Info.plist';
-    const result = writePlist(project, '/', plist);
+    writePlist(project, '/', plist);
     const infoPlist = readFileSync(infoPlistPath).toString();
     expect(fs.writeFileSync).toHaveBeenCalledWith(plistPath, infoPlist);
   });

link/ios/copyAssets.js

@@ -10,7 +10,6 @@
 const fs = require('fs-extra');
 const path = require('path');
 const xcode = require('xcode');
-const log = require('npmlog');
 const groupFilesByType = require('../groupFilesByType');
 const createGroupWithMessage = require('./createGroupWithMessage');
 const getPlist = require('./getPlist');

link/ios/unregisterNativeModule.js

@@ -14,7 +14,6 @@ const difference = require('lodash').difference;
 const isEmpty = require('lodash').isEmpty;
 
 const getGroup = require('./getGroup');
-const getProducts = require('./getProducts');
 const getTargets = require('./getTargets');
 const getHeadersInFolder = require('./getHeadersInFolder');
 const getHeaderSearchPath = require('./getHeaderSearchPath');

templates/HelloWorld/__tests__/App.js

@@ -8,5 +8,5 @@ import App from '../App';
 import renderer from 'react-test-renderer';
 
 it('renders correctly', () => {
-  const tree = renderer.create(<App />);
+  renderer.create(<App />);
 });

upgrade/upgrade.js

@@ -13,9 +13,7 @@ const chalk = require('chalk');
 const copyProjectTemplateAndReplace = require('../generator/copyProjectTemplateAndReplace');
 const fs = require('fs');
 const path = require('path');
-const printRunInstructions = require('../generator/printRunInstructions');
 const semver = require('semver');
-const yarn = require('../util/yarn');
 
 /**
  * Migrate application to a new version of React Native.