Prefer const wherever possible

Summary:
Non-final identifiers make code harder to understand.
This is particularly true for JavaScript where even the *type*
can change as a value gets reassigned later.

This enforces to use `const` whereever possible, but doesn't
"outlaw" `let`. Mixed destructuring is also still allowed.

Used `eslint --fix` to change all existing cases.

Reviewed By: jknoxville

Differential Revision: D16131329

fbshipit-source-id: 2eceaca7c603b71b36e005be5d135e1849f2518d

.eslintrc.js

@@ -22,8 +22,9 @@ module.exports = {
     'no-bitwise': 0, // bitwise operations needed in some places
     'consistent-return': 0,
     'no-var': 2,
-    'max-len': 0, // let's take prettier take care of this
+    'prefer-const': [2, {destructuring: 'all'}],
-    indent: 0, // let's take prettier take care of this
+    'max-len': 0, // lets prettier take care of this
+    indent: 0, // lets prettier take care of this
     'no-console': 0, // we're setting window.console in App.js
     'prefer-promise-reject-errors': 1,
 

headless/index.js

@@ -146,7 +146,7 @@ async function exitActions(
   store: Store,
 ): Promise<void> {
   const {metrics, exit} = userArguments;
-  for (let exitAction of exitClosures) {
+  for (const exitAction of exitClosures) {
     try {
       const action = await exitAction(userArguments, store);
       if (action.exit) {

src/NotificationsHub.js

@@ -355,7 +355,7 @@ const shadow = (props, hover) => {
   if (props.inactive) {
     return `inset 0 0 0 1px ${colors.light10}`;
   }
-  let shadow = ['1px 1px 5px rgba(0,0,0,0.1)'];
+  const shadow = ['1px 1px 5px rgba(0,0,0,0.1)'];
   if (props.isSelected) {
     shadow.push(`inset 0 0 0 2px ${colors.macOSTitleBarIconSelected}`);
   }

src/chrome/LocationsButton.js

@@ -29,7 +29,7 @@ class LocationsButton extends Component<Props> {
   goToLocation = (location: string) => {
     const {selectedDevice} = this.props;
     if (selectedDevice instanceof AndroidDevice) {
-      let shellCommand = `am start ${location}`;
+      const shellCommand = `am start ${location}`;
       selectedDevice.adb.shell(selectedDevice.serial, shellCommand);
     }
   };

src/chrome/PluginDebugger.js

@@ -161,7 +161,7 @@ class PluginDebugger extends Component<Props> {
   }
 
   getRows(): Array<TableBodyRow> {
-    let rows: Array<TableBodyRow> = [];
+    const rows: Array<TableBodyRow> = [];
 
     // bundled plugins are loaded from the defaultPlugins directory within
     // Flipper's package.

src/dispatcher/__tests__/deeplinkURLParsing.node.js

@@ -9,24 +9,24 @@ import {uriComponents} from '../application.js';
 
 test('test parsing of deeplink URL', () => {
   const url = 'flipper://app/plugin/meta/data';
-  let components = uriComponents(url);
+  const components = uriComponents(url);
   expect(components).toEqual(['app', 'plugin', 'meta/data']);
 });
 
 test('test parsing of deeplink URL when arguments are less', () => {
   const url = 'flipper://app/';
-  let components = uriComponents(url);
+  const components = uriComponents(url);
   expect(components).toEqual(['app']);
 });
 
 test('test parsing of deeplink URL when url is null', () => {
   // $FlowFixMe
-  let components = uriComponents(null);
+  const components = uriComponents(null);
   expect(components).toEqual([]);
 });
 
 test('test parsing of deeplink URL when pattern does not match', () => {
   const url = 'Some random string';
-  let components = uriComponents(url);
+  const components = uriComponents(url);
   expect(components).toEqual([]);
 });

src/dispatcher/iOSDevice.js

@@ -160,7 +160,7 @@ async function checkXcodeVersionMismatch() {
     let {stdout: xcodeCLIVersion} = await exec('xcode-select -p');
     xcodeCLIVersion = xcodeCLIVersion.trim();
     const {stdout} = await exec('ps aux | grep CoreSimulator');
-    for (let line of stdout.split('\n')) {
+    for (const line of stdout.split('\n')) {
       const match = line.match(
         /\/Applications\/Xcode[^/]*\.app\/Contents\/Developer/,
       );

src/plugins/cpu/TemperatureTable.js

@@ -49,7 +49,7 @@ export default class TemperatureTable extends Component<TemperatureTableProps> {
   };
 
   buildRows = () => {
-    let rows = [];
+    const rows = [];
     for (const tz of Object.keys(this.props.temperatureMap).sort()) {
       rows.push(this.buildRow(tz, this.props.temperatureMap[tz]));
     }

src/plugins/cpu/index.js

@@ -6,7 +6,7 @@
  */
 
 import {FlipperDevicePlugin, Device} from 'flipper';
-let adb = require('adbkit-fb');
+const adb = require('adbkit-fb');
 import TemperatureTable from './TemperatureTable.js';
 
 import {
@@ -107,7 +107,7 @@ const Heading = styled('div')({
 
 // check if str is a number
 function isNormalInteger(str) {
-  let n = Math.floor(Number(str));
+  const n = Math.floor(Number(str));
   return String(n) === str && n >= 0;
 }
 
@@ -145,7 +145,7 @@ export default class CPUFrequencyTable extends FlipperDevicePlugin<CPUState> {
   }
 
   init() {
-    let device = ((this.device: any): AndroidDevice);
+    const device = ((this.device: any): AndroidDevice);
     this.adbClient = device.adb;
 
     this.updateHardwareInfo();
@@ -153,9 +153,9 @@ export default class CPUFrequencyTable extends FlipperDevicePlugin<CPUState> {
 
     // check how many cores we have on this device
     this.executeShell((output: string) => {
-      let idx = output.indexOf('-');
+      const idx = output.indexOf('-');
-      let cpuFreq = [];
+      const cpuFreq = [];
-      let count = parseInt(output.substring(idx + 1), 10) + 1;
+      const count = parseInt(output.substring(idx + 1), 10) + 1;
       for (let i = 0; i < count; ++i) {
         cpuFreq[i] = {
           cpu_id: i,
@@ -187,8 +187,8 @@ export default class CPUFrequencyTable extends FlipperDevicePlugin<CPUState> {
 
   updateCoreFrequency = (core: number, type: string) => {
     this.executeShell((output: string) => {
-      let cpuFreq = this.state.cpuFreq;
+      const cpuFreq = this.state.cpuFreq;
-      let newFreq = isNormalInteger(output) ? parseInt(output, 10) : -1;
+      const newFreq = isNormalInteger(output) ? parseInt(output, 10) : -1;
 
       // update table only if frequency changed
       if (cpuFreq[core][type] != newFreq) {
@@ -207,12 +207,12 @@ export default class CPUFrequencyTable extends FlipperDevicePlugin<CPUState> {
 
   updateAvailableFrequencies = (core: number) => {
     this.executeShell((output: string) => {
-      let cpuFreq = this.state.cpuFreq;
+      const cpuFreq = this.state.cpuFreq;
-      let freqs = output.split(' ').map((num: string) => {
+      const freqs = output.split(' ').map((num: string) => {
         return parseInt(num, 10);
       });
       cpuFreq[core].scaling_available_freqs = freqs;
-      let maxFreq = cpuFreq[core].scaling_max_freq;
+      const maxFreq = cpuFreq[core].scaling_max_freq;
       if (maxFreq > 0 && freqs.indexOf(maxFreq) == -1) {
         freqs.push(maxFreq); // always add scaling max to available frequencies
       }
@@ -224,7 +224,7 @@ export default class CPUFrequencyTable extends FlipperDevicePlugin<CPUState> {
 
   updateCoreGovernor = (core: number) => {
     this.executeShell((output: string) => {
-      let cpuFreq = this.state.cpuFreq;
+      const cpuFreq = this.state.cpuFreq;
       if (output.toLowerCase().includes('no such file')) {
         cpuFreq[core].scaling_governor = 'N/A';
       } else {
@@ -238,7 +238,7 @@ export default class CPUFrequencyTable extends FlipperDevicePlugin<CPUState> {
 
   readAvailableGovernors = (core: number) => {
     this.executeShell((output: string) => {
-      let cpuFreq = this.state.cpuFreq;
+      const cpuFreq = this.state.cpuFreq;
       cpuFreq[core].scaling_available_governors = output.split(' ');
 
       this.setState({
@@ -248,7 +248,7 @@ export default class CPUFrequencyTable extends FlipperDevicePlugin<CPUState> {
   };
 
   readCoreFrequency = (core: number) => {
-    let freq = this.state.cpuFreq[core];
+    const freq = this.state.cpuFreq[core];
     if (freq.cpuinfo_max_freq < 0) {
       this.updateCoreFrequency(core, 'cpuinfo_max_freq');
     }
@@ -296,21 +296,21 @@ export default class CPUFrequencyTable extends FlipperDevicePlugin<CPUState> {
   };
 
   readThermalZones = () => {
-    let thermal_dir = '/sys/class/thermal/';
+    const thermal_dir = '/sys/class/thermal/';
-    let map = {};
+    const map = {};
     this.executeShell(async (output: string) => {
       if (output.toLowerCase().includes('permission denied')) {
         this.setState({thermalAccessible: false});
         return;
       }
-      let dirs = output.split(/\s/);
+      const dirs = output.split(/\s/);
-      let promises = [];
+      const promises = [];
       for (let d of dirs) {
         d = d.trim();
         if (d.length == 0) {
           continue;
         }
-        let path = thermal_dir + d;
+        const path = thermal_dir + d;
         promises.push(this.readThermalZone(path, d, map));
       }
       await Promise.all(promises);
@@ -374,7 +374,7 @@ export default class CPUFrequencyTable extends FlipperDevicePlugin<CPUState> {
   };
 
   cleanup = () => {
-    let cpuFreq = this.state.cpuFreq;
+    const cpuFreq = this.state.cpuFreq;
     for (let i = 0; i < this.state.cpuCount; ++i) {
       cpuFreq[i].scaling_cur_freq = -1;
       cpuFreq[i].scaling_min_freq = -1;
@@ -394,7 +394,7 @@ export default class CPUFrequencyTable extends FlipperDevicePlugin<CPUState> {
   };
 
   buildRow = (freq: CPUFrequency, idx: number) => {
-    let selected = this.state.selectedIds.indexOf(idx) >= 0;
+    const selected = this.state.selectedIds.indexOf(idx) >= 0;
     let style = {};
     if (freq.scaling_cur_freq == -2) {
       style = {
@@ -466,11 +466,11 @@ export default class CPUFrequencyTable extends FlipperDevicePlugin<CPUState> {
     if (freq.scaling_available_freqs.length == 0) {
       return <Text>N/A</Text>;
     }
-    let info = freq;
+    const info = freq;
     return (
       <Text>
         {freq.scaling_available_freqs.map((freq, idx) => {
-          let style = {};
+          const style = {};
           if (
             freq == info.scaling_cur_freq ||
             freq == info.scaling_min_freq ||
@@ -519,15 +519,15 @@ export default class CPUFrequencyTable extends FlipperDevicePlugin<CPUState> {
 
   sidebarRows = (id: number) => {
     let availableFreqTitle = 'Scaling Available Frequencies';
-    let selected = this.state.cpuFreq[id];
+    const selected = this.state.cpuFreq[id];
     if (selected.scaling_available_freqs.length > 0) {
       availableFreqTitle +=
         ' (' + selected.scaling_available_freqs.length.toString() + ')';
     }
 
-    let keys = [availableFreqTitle, 'Scaling Available Governors'];
+    const keys = [availableFreqTitle, 'Scaling Available Governors'];
 
-    let vals = [
+    const vals = [
       this.buildAvailableFreqList(selected),
       this.buildAvailableGovList(selected),
     ];
@@ -540,8 +540,8 @@ export default class CPUFrequencyTable extends FlipperDevicePlugin<CPUState> {
     if (!this.state.displayCPUDetail || this.state.selectedIds.length == 0) {
       return null;
     }
-    let id = this.state.selectedIds[0];
+    const id = this.state.selectedIds[0];
-    let cols = {
+    const cols = {
       key: {
         value: 'key',
         resizable: true,
@@ -551,7 +551,7 @@ export default class CPUFrequencyTable extends FlipperDevicePlugin<CPUState> {
         resizable: true,
       },
     };
-    let colSizes = {
+    const colSizes = {
       key: '35%',
       value: 'flex',
     };

src/plugins/crash_reporter/__tests__/testCrashReporterPlugin.electron.js

@@ -346,20 +346,20 @@ test('test parsing of path when a regex is not present', () => {
 });
 test('test shouldShowCrashNotification function for all correct inputs', () => {
   const device = new BaseDevice('TH1S-15DEV1CE-1D', 'emulator', 'test device');
-  let content =
+  const content =
     'Blaa Blaaa \n Blaa Blaaa \n Path:  path/to/simulator/TH1S-15DEV1CE-1D/App Name.app/App Name \n Blaa Blaa \n Blaa Blaa';
   const shouldShowNotification = shouldShowCrashNotification(device, content);
   expect(shouldShowNotification).toEqual(true);
 });
 test('test shouldShowCrashNotification function for all correct inputs but incorrect id', () => {
   const device = new BaseDevice('TH1S-15DEV1CE-1D', 'emulator', 'test device');
-  let content =
+  const content =
     'Blaa Blaaa \n Blaa Blaaa \n Path:  path/to/simulator/TH1S-1598DEV1CE-2D/App Name.app/App Name \n Blaa Blaa \n Blaa Blaa';
   const shouldShowNotification = shouldShowCrashNotification(device, content);
   expect(shouldShowNotification).toEqual(false);
 });
 test('test shouldShowCrashNotification function for undefined device', () => {
-  let content =
+  const content =
     'Blaa Blaaa \n Blaa Blaaa \n Path:  path/to/simulator/TH1S-1598DEV1CE-2D/App Name.app/App Name \n Blaa Blaa \n Blaa Blaa';
   const shouldShowNotification = shouldShowCrashNotification(null, content);
   expect(shouldShowNotification).toEqual(false);

src/plugins/crash_reporter/index.js

@@ -544,7 +544,7 @@ export default class CrashReporterPlugin extends FlipperDevicePlugin<
   };
 
   static trimCallStackIfPossible = (callstack: string): string => {
-    let regex = /Application Specific Information:/;
+    const regex = /Application Specific Information:/;
     const query = regex.exec(callstack);
     return query ? callstack.substring(0, query.index) : callstack;
   };
@@ -555,7 +555,7 @@ export default class CrashReporterPlugin extends FlipperDevicePlugin<
     persistedState: PersistedState,
   ): Array<Notification> => {
     const filteredCrashes = persistedState.crashes.filter(crash => {
-      let ignore = !crash.name && !crash.reason;
+      const ignore = !crash.name && !crash.reason;
       if (ignore) {
         console.error('Ignored the notification for the crash', crash);
       }
@@ -563,7 +563,7 @@ export default class CrashReporterPlugin extends FlipperDevicePlugin<
     });
     return filteredCrashes.map((crash: Crash) => {
       const id = crash.notificationID;
-      let name: string = crash.name || crash.reason;
+      const name: string = crash.name || crash.reason;
       let title: string = 'CRASH: ' + truncate(name, 50);
       title = `${
         name == crash.reason

src/plugins/fresco/index.js

@@ -302,7 +302,7 @@ export default class extends FlipperPlugin<PluginState, *, PersistedState> {
       this.props.setPersistedState({imagesMap: images}),
     );
 
-    let images = this.filterImages(
+    const images = this.filterImages(
       this.props.persistedState.images,
       this.props.persistedState.events,
       this.state.selectedSurface,

src/plugins/layout/ProxyArchiveClient.js

@@ -28,7 +28,7 @@ function constructSearchResultTree(
   AXMode: boolean,
   AXNode: ?Element,
 ): SearchResultTree {
-  let searchResult = {
+  const searchResult = {
     id: node.id,
     isMatch,
     hasChildren: children.length > 0,
@@ -118,7 +118,7 @@ class ProxyArchiveClient {
         }
         const {ids} = paramaters;
         const arr: Array<Element> = [];
-        for (let id: ElementID of ids) {
+        for (const id: ElementID of ids) {
           arr.push(this.persistedState.elements[id]);
         }
         return Promise.resolve({elements: arr});
@@ -129,7 +129,7 @@ class ProxyArchiveClient {
         }
         const {ids} = paramaters;
         const arr: Array<Element> = [];
-        for (let id: ElementID of ids) {
+        for (const id: ElementID of ids) {
           arr.push(this.persistedState.AXelements[id]);
         }
         return Promise.resolve({elements: arr});

src/plugins/layout/__tests__/ProxyArchiveClient.node.js

@@ -49,7 +49,7 @@ function constructPersistedState(axMode: boolean): PersistedState {
 let state = constructPersistedState(false);
 
 function populateChildren(state: PersistedState, axMode: boolean) {
-  let elements = {};
+  const elements = {};
   elements['root'] = constructElement('root', 'root view', [
     'child0',
     'child1',
@@ -95,7 +95,7 @@ beforeEach(() => {
 });
 
 test('test the searchNode for root in axMode false', async () => {
-  let searchResult: ?SearchResultTree = await searchNodes(
+  const searchResult: ?SearchResultTree = await searchNodes(
     state.elements['root'],
     'root',
     false,
@@ -115,7 +115,7 @@ test('test the searchNode for root in axMode false', async () => {
 test('test the searchNode for root in axMode true', async () => {
   state = constructPersistedState(true);
   populateChildren(state, true);
-  let searchResult: ?SearchResultTree = await searchNodes(
+  const searchResult: ?SearchResultTree = await searchNodes(
     state.AXelements['root'],
     'RoOT',
     true,
@@ -133,7 +133,7 @@ test('test the searchNode for root in axMode true', async () => {
 });
 
 test('test the searchNode which matches just one child', async () => {
-  let searchResult: ?SearchResultTree = await searchNodes(
+  const searchResult: ?SearchResultTree = await searchNodes(
     state.elements['root'],
     'child0_child0',
     false,
@@ -169,14 +169,14 @@ test('test the searchNode which matches just one child', async () => {
 });
 
 test('test the searchNode for which matches multiple child', async () => {
-  let searchResult: ?SearchResultTree = await searchNodes(
+  const searchResult: ?SearchResultTree = await searchNodes(
     state.elements['root'],
     'child0',
     false,
     state,
   );
   expect(searchResult).toBeDefined();
-  let expectedSearchResult = {
+  const expectedSearchResult = {
     id: 'root',
     isMatch: false,
     hasChildren: true,
@@ -231,14 +231,14 @@ test('test the searchNode for which matches multiple child', async () => {
 });
 
 test('test the searchNode, it should not be case sensitive', async () => {
-  let searchResult: ?SearchResultTree = await searchNodes(
+  const searchResult: ?SearchResultTree = await searchNodes(
     state.elements['root'],
     'ChIlD0',
     false,
     state,
   );
   expect(searchResult).toBeDefined();
-  let expectedSearchResult = {
+  const expectedSearchResult = {
     id: 'root',
     isMatch: false,
     hasChildren: true,
@@ -293,7 +293,7 @@ test('test the searchNode, it should not be case sensitive', async () => {
 });
 
 test('test the searchNode for non existent query', async () => {
-  let searchResult: ?SearchResultTree = await searchNodes(
+  const searchResult: ?SearchResultTree = await searchNodes(
     state.elements['root'],
     'Unknown query',
     false,
@@ -303,22 +303,22 @@ test('test the searchNode for non existent query', async () => {
 });
 
 test('test the call method with getRoot', async () => {
-  let proxyClient = new ProxyArchiveClient(state);
+  const proxyClient = new ProxyArchiveClient(state);
-  let root: Element = await proxyClient.call('getRoot');
+  const root: Element = await proxyClient.call('getRoot');
   expect(root).toEqual(state.elements['root']);
 });
 
 test('test the call method with getAXRoot', async () => {
   state = constructPersistedState(true);
   populateChildren(state, true);
-  let proxyClient = new ProxyArchiveClient(state);
+  const proxyClient = new ProxyArchiveClient(state);
-  let root: Element = await proxyClient.call('getAXRoot');
+  const root: Element = await proxyClient.call('getAXRoot');
   expect(root).toEqual(state.AXelements['root']);
 });
 
 test('test the call method with getNodes', async () => {
-  let proxyClient = new ProxyArchiveClient(state);
+  const proxyClient = new ProxyArchiveClient(state);
-  let nodes: Array<Element> = await proxyClient.call('getNodes', {
+  const nodes: Array<Element> = await proxyClient.call('getNodes', {
     ids: ['child0_child1', 'child1_child0'],
   });
   expect(nodes).toEqual({
@@ -350,8 +350,8 @@ test('test the call method with getNodes', async () => {
 test('test the call method with getAXNodes', async () => {
   state = constructPersistedState(true);
   populateChildren(state, true);
-  let proxyClient = new ProxyArchiveClient(state);
+  const proxyClient = new ProxyArchiveClient(state);
-  let nodes: Array<Element> = await proxyClient.call('getAXNodes', {
+  const nodes: Array<Element> = await proxyClient.call('getAXNodes', {
     ids: ['child0_child1', 'child1_child0'],
   });
   expect(nodes).toEqual({
@@ -381,7 +381,7 @@ test('test the call method with getAXNodes', async () => {
 });
 
 test('test different methods of calls with no params', async () => {
-  let proxyClient = new ProxyArchiveClient(state);
+  const proxyClient = new ProxyArchiveClient(state);
   await expect(proxyClient.call('getNodes')).rejects.toThrow(
     new Error('Called getNodes with no params'),
   );
@@ -408,6 +408,6 @@ test('test different methods of calls with no params', async () => {
 });
 
 test('test call method isConsoleEnabled', () => {
-  let proxyClient = new ProxyArchiveClient(state);
+  const proxyClient = new ProxyArchiveClient(state);
   return expect(proxyClient.call('isConsoleEnabled')).resolves.toBe(false);
 });

src/plugins/leak_canary/index.js

@@ -69,7 +69,7 @@ export default class LeakCanary extends FlipperPlugin<State> {
       // collapsed state of the tree view
       const newLeaks = processLeaks(results.leaks.slice(this.state.leaksCount));
 
-      let leaks = this.state.leaks;
+      const leaks = this.state.leaks;
       for (let i = 0; i < newLeaks.length; i++) {
         leaks.push(newLeaks[i]);
       }

src/plugins/leak_canary/processLeakString.js

@@ -53,8 +53,8 @@ function generateFieldsList(
   lines: string[],
   i: number,
 ): {|staticFields: {}, instanceFields: {}, packages: {}|} {
-  let staticFields = {};
+  const staticFields = {};
-  let instanceFields = {};
+  const instanceFields = {};
 
   let staticValues = {};
   let instanceValues = {};
@@ -62,7 +62,7 @@ function generateFieldsList(
   let elementId = -1;
   let elementIdStr = String(-1);
 
-  let packages = {};
+  const packages = {};
 
   // Process everything between Details and Excluded Refs
   while (
@@ -127,8 +127,8 @@ function processLeak(output: Leak[], leakInfo: string): Leak[] {
 
   // Elements shows a Object's classname and package, wheras elementsSimple shows
   // just its classname
-  let elements = {};
+  const elements = {};
-  let elementsSimple = {};
+  const elementsSimple = {};
 
   let rootElementId = '';
 

src/plugins/logs/index.js

@@ -429,7 +429,7 @@ export default class LogTable extends FlipperDevicePlugin<
     if (highlightedRows.size <= 0) {
       // Check if the individual lines in the deeplinkPayload is matched or not.
       const arr = deepLinkPayload.split('\n');
-      for (let msg of arr) {
+      for (const msg of arr) {
         for (let i = rows.length - 1; i >= 0; i--) {
           if (rows[i].filterValue && rows[i].filterValue.includes(msg)) {
             highlightedRows.add(rows[i].key);

src/plugins/network/__tests__/requestToCurlCommand.node.js

@@ -129,7 +129,7 @@ test('convertRequestToCurlCommand: malicious POST data', () => {
 });
 
 test('convertRequestToCurlCommand: control characters', () => {
-  let request: Request = {
+  const request: Request = {
     id: 'request id',
     timestamp: 1234567890,
     method: 'GET',
@@ -138,7 +138,7 @@ test('convertRequestToCurlCommand: control characters', () => {
     data: btoa('some=\u0007 \u0009 \u000C \u001B&other=param'),
   };
 
-  let command = convertRequestToCurlCommand(request);
+  const command = convertRequestToCurlCommand(request);
   expect(command).toEqual(
     "curl -v -X GET 'https://fbflipper.com/' -d $'some=\\u07 \\u09 \\u0c \\u1b&other=param'",
   );

src/plugins/shared_preferences/index.js

@@ -90,8 +90,8 @@ export default class extends FlipperPlugin<SharedPreferencesState> {
 
   reducers = {
     UpdateSharedPreferences(state: SharedPreferencesState, results: Object) {
-      let update = results.update;
+      const update = results.update;
-      let entry = state.sharedPreferences[update.name] || {changesList: []};
+      const entry = state.sharedPreferences[update.name] || {changesList: []};
       entry.preferences = update.preferences;
       state.sharedPreferences[update.name] = entry;
       return {
@@ -170,7 +170,7 @@ export default class extends FlipperPlugin<SharedPreferencesState> {
         preferenceValue: newValue,
       })
       .then((results: SharedPreferences) => {
-        let update = {
+        const update = {
           name: this.state.selectedPreferences,
           preferences: results,
         };

src/reducers/connections.js

@@ -143,7 +143,7 @@ const reducer = (state: State = INITAL_STATE, action: Action): State => {
         selectedPlugin: DEFAULT_PLUGIN,
       };
 
-      let canBeDefaultDevice = !DEFAULT_DEVICE_BLACKLIST.some(
+      const canBeDefaultDevice = !DEFAULT_DEVICE_BLACKLIST.some(
         blacklistedDevice => payload instanceof blacklistedDevice,
       );
 
@@ -272,7 +272,7 @@ const reducer = (state: State = INITAL_STATE, action: Action): State => {
     case 'CLIENT_REMOVED': {
       const {payload} = action;
 
-      let selected = {};
+      const selected = {};
       if (state.selectedApp === payload) {
         selected.selectedApp = null;
         selected.selectedPlugin = DEFAULT_PLUGIN;

src/server.js

@@ -76,7 +76,7 @@ export default class Server extends EventEmitter {
   ): Promise<RSocketServer> {
     const server = this;
     return new Promise((resolve, reject) => {
-      let rsServer;
+      let rsServer; // eslint-disable-line prefer-const
       const serverFactory = onConnect => {
         const transportServer = sslConfig
           ? tls.createServer(sslConfig, socket => {

src/utils/__tests__/crashReporterUtility.node.js

@@ -18,56 +18,56 @@ function getAndroidLog(
 
 test('test shouldParseAndroidLog function for type error and tag is AndroidRuntime', () => {
   const referenceDate = new Date();
-  let log: DeviceLogEntry = getAndroidLog(
+  const log: DeviceLogEntry = getAndroidLog(
     new Date(referenceDate.getTime() + 10000), //This log arrives 10 secs after the refernce time
     'error',
     'AndroidRuntime',
     'Possible runtime crash',
   );
-  let shouldParseTheLog = shouldParseAndroidLog(log, referenceDate);
+  const shouldParseTheLog = shouldParseAndroidLog(log, referenceDate);
   expect(shouldParseTheLog).toEqual(true);
 });
 test('test shouldParseAndroidLog function for type non-error', () => {
   const referenceDate = new Date();
-  let log: DeviceLogEntry = getAndroidLog(
+  const log: DeviceLogEntry = getAndroidLog(
     new Date(referenceDate.getTime() + 10000), //This log arrives 10 secs after the refernce time
     'debug',
     'fb4a.activitymanager',
     'Possible debug info in activitymanager',
   );
-  let shouldParseTheLog = shouldParseAndroidLog(log, referenceDate);
+  const shouldParseTheLog = shouldParseAndroidLog(log, referenceDate);
   expect(shouldParseTheLog).toEqual(false);
 });
 test('test shouldParseAndroidLog function for the older android log', () => {
   const referenceDate = new Date();
-  let log: DeviceLogEntry = getAndroidLog(
+  const log: DeviceLogEntry = getAndroidLog(
     new Date(referenceDate.getTime() - 10000), //This log arrives 10 secs before the refernce time
     'error',
     'fb4a.activitymanager',
     'Possible error info in activitymanager',
   );
-  let shouldParseTheLog = shouldParseAndroidLog(log, referenceDate);
+  const shouldParseTheLog = shouldParseAndroidLog(log, referenceDate);
   expect(shouldParseTheLog).toEqual(false);
 });
 test('test shouldParseAndroidLog function for the fatal log', () => {
   const referenceDate = new Date();
-  let log: DeviceLogEntry = getAndroidLog(
+  const log: DeviceLogEntry = getAndroidLog(
     new Date(referenceDate.getTime() + 10000), //This log arrives 10 secs after the refernce time
     'fatal',
     'arbitrary tag',
     'Possible error info in activitymanager',
   );
-  let shouldParseTheLog = shouldParseAndroidLog(log, referenceDate);
+  const shouldParseTheLog = shouldParseAndroidLog(log, referenceDate);
   expect(shouldParseTheLog).toEqual(true);
 });
 test('test shouldParseAndroidLog function for the error log which does not staisfy our tags check', () => {
   const referenceDate = new Date();
-  let log: DeviceLogEntry = getAndroidLog(
+  const log: DeviceLogEntry = getAndroidLog(
     new Date(referenceDate.getTime() + 10000), //This log arrives 10 secs after the refernce time
     'error',
     'arbitrary tag',
     'Possible error info in fb4a',
   );
-  let shouldParseTheLog = shouldParseAndroidLog(log, referenceDate);
+  const shouldParseTheLog = shouldParseAndroidLog(log, referenceDate);
   expect(shouldParseTheLog).toEqual(false);
 });

src/utils/__tests__/exportData.electron.js

@@ -35,7 +35,7 @@ function generateClientIdentifierWithSalt(
   identifier: string,
   salt: string,
 ): string {
-  let array = identifier.split('#');
+  const array = identifier.split('#');
   const serial = array.pop();
   return array.join('#') + '#' + salt + '-' + serial;
 }
@@ -198,7 +198,7 @@ test('test processStore function for an iOS device connected with client plugin
   expect(json).toBeDefined();
   //$FlowFixMe Flow doesn't that its a test and the assertion for null is already done
   const {pluginStates} = json.store;
-  let expectedPluginState = {
+  const expectedPluginState = {
     [generateClientIdentifierWithSalt(clientIdentifier, 'salt')]: {
       msg: 'Test plugin',
     },
@@ -258,7 +258,7 @@ test('test processStore function to have only the client for the selected device
   //$FlowFixMe Flow doesn't that its a test and the assertion for null is already added
   const {clients} = json;
   const {pluginStates} = json.store;
-  let expectedPluginState = {
+  const expectedPluginState = {
     [generateClientIdentifierWithSalt(selectedDeviceClientIdentifier, 'salt') +
     '#testapp']: {
       msg: 'Test plugin selected device',
@@ -313,7 +313,7 @@ test('test processStore function to have multiple clients for the selected devic
   //$FlowFixMe Flow doesn't that its a test and the assertion for null is already added
   const {clients} = json;
   const {pluginStates} = json.store;
-  let expectedPluginState = {
+  const expectedPluginState = {
     [generateClientIdentifierWithSalt(clientIdentifierApp1, 'salt') +
     '#testapp1']: {
       msg: 'Test plugin App1',
@@ -355,7 +355,7 @@ test('test processStore function for device plugin state and no clients', async
   //$FlowFixMe Flow doesn't that its a test and the assertion for null is already done
   const {pluginStates} = json.store;
   const {clients} = json;
-  let expectedPluginState = {
+  const expectedPluginState = {
     'salt-serial#TestDevicePlugin': {msg: 'Test Device plugin'},
   };
   expect(pluginStates).toEqual(expectedPluginState);

src/utils/__tests__/pluginUtils.node.js

@@ -41,18 +41,18 @@ function mockPluginDefinition(name: string): PluginDefinition {
 }
 
 test('getActivePluginNames with the plugins getting excluded', () => {
-  let state = mockPluginState(
+  const state = mockPluginState(
     [mockPluginDefinition('DevicePlugin1')],
     [mockPluginDefinition('ClientPlugin1')],
     [[mockPluginDefinition('DevicePlugin2'), 'DevicePlugin2']],
   );
-  let list = getActivePluginNames(state);
+  const list = getActivePluginNames(state);
   expect(list).toEqual(['ClientPlugin2']);
 });
 
 test('getActivePluginNames with the no plugins getting excluded', () => {
-  let state = mockPluginState([], [], []);
+  const state = mockPluginState([], [], []);
-  let list = getActivePluginNames(state);
+  const list = getActivePluginNames(state);
   expect(list).toEqual([
     'ClientPlugin1',
     'ClientPlugin2',

src/utils/__tests__/promiseTimeout.node.js

@@ -7,10 +7,10 @@
 import promiseTimeout from '../promiseTimeout';
 
 test('test promiseTimeout for timeout to happen', () => {
-  let promise = promiseTimeout(
+  const promise = promiseTimeout(
     200,
     new Promise((resolve, reject) => {
-      let id = setTimeout(() => {
+      const id = setTimeout(() => {
         clearTimeout(id);
         resolve();
       }, 500);
@@ -22,10 +22,10 @@ test('test promiseTimeout for timeout to happen', () => {
 });
 
 test('test promiseTimeout for timeout not to happen', () => {
-  let promise = promiseTimeout(
+  const promise = promiseTimeout(
     200,
     new Promise((resolve, reject) => {
-      let id = setTimeout(() => {
+      const id = setTimeout(() => {
         clearTimeout(id);
         resolve();
       }, 100);

src/utils/__tests__/serialization.node.js

@@ -19,12 +19,12 @@ class TestObject extends Object {
   set: ?Set<any>;
 }
 test('test makeObjectSerializable function for unnested object with no Set and Map', () => {
-  let obj = {key1: 'value1', key2: 'value2'};
+  const obj = {key1: 'value1', key2: 'value2'};
   const output = makeObjectSerializable(obj);
   expect(output).toEqual(obj);
 
   // Testing numbers
-  let obj2 = {key1: 1, key2: 2};
+  const obj2 = {key1: 1, key2: 2};
   const output2 = makeObjectSerializable(obj2);
   expect(output2).toEqual(obj2);
 });
@@ -36,27 +36,27 @@ test('makeObjectSerializable function for unnested object with values which retu
 });
 
 test('test deserializeObject function for unnested object with no Set and Map', () => {
-  let obj = {key1: 'value1', key2: 'value2'};
+  const obj = {key1: 'value1', key2: 'value2'};
   const output = deserializeObject(obj);
   expect(output).toEqual(obj);
 
   // Testing numbers
-  let obj2 = {key1: 1, key2: 2};
+  const obj2 = {key1: 1, key2: 2};
   const output2 = deserializeObject(obj2);
   expect(output2).toEqual(obj2);
 });
 
 test('test makeObjectSerializable and deserializeObject function for nested object with no Set and Map', () => {
-  let subObj = {key1: 'value1', key2: 'value2'};
+  const subObj = {key1: 'value1', key2: 'value2'};
-  let subObj2 = {key21: 'value21', key22: 'value22'};
+  const subObj2 = {key21: 'value21', key22: 'value22'};
-  let obj = {key1: subObj, key2: subObj2};
+  const obj = {key1: subObj, key2: subObj2};
   const output = makeObjectSerializable(obj);
   expect(output).toEqual(obj);
   expect(deserializeObject(output)).toEqual(obj);
 
-  let subObjNum = {key1: 1, key2: 2};
+  const subObjNum = {key1: 1, key2: 2};
-  let subObjNum2 = {key21: 21, key22: 22};
+  const subObjNum2 = {key21: 21, key22: 22};
-  let obj2 = {key1: subObjNum, key2: subObjNum2};
+  const obj2 = {key1: subObjNum, key2: subObjNum2};
   const output2 = makeObjectSerializable(obj2);
   expect(output2).toEqual(obj2);
   expect(deserializeObject(output2)).toEqual(obj2);
@@ -184,19 +184,19 @@ test('test makeObjectSerializable and deserializeObject function for custom Obje
 });
 
 test('test makeObjectSerializable and deserializeObject function for Array as input', () => {
-  let arr = [1, 2, 4, 5];
+  const arr = [1, 2, 4, 5];
   const output = makeObjectSerializable(arr);
   expect(output).toEqual(arr);
   expect(deserializeObject(output)).toEqual(arr);
 
-  let arrMap = [
+  const arrMap = [
     new Map([['a1', 'v1'], ['a2', 'v2']]),
     new Map([['b1', 'v1'], ['b2', 'v2']]),
     new Map([['c1', 'v1'], ['c2', 'v2']]),
     new Map([['d1', 'v1'], ['d2', 'v2']]),
   ];
 
-  let expectedArr = [
+  const expectedArr = [
     {
       __flipper_object_type__: 'Map',
       data: [['a1', 'v1'], ['a2', 'v2']],
@@ -218,7 +218,7 @@ test('test makeObjectSerializable and deserializeObject function for Array as in
   expect(outputMap).toEqual(expectedArr);
   expect(deserializeObject(outputMap)).toEqual(arrMap);
 
-  let arrStr = ['first', 'second', 'third', 'fourth'];
+  const arrStr = ['first', 'second', 'third', 'fourth'];
   const outputStr = makeObjectSerializable(arrStr);
   expect(outputStr).toEqual(arrStr);
   expect(deserializeObject(outputStr)).toEqual(arrStr);

src/utils/exportData.js

@@ -70,8 +70,8 @@ export function processPluginStates(
   devicePlugins: Map<string, Class<FlipperDevicePlugin<>>>,
 ): PluginStatesState {
   let pluginStates = {};
-  for (let key in allPluginStates) {
+  for (const key in allPluginStates) {
-    let keyArray = key.split('#');
+    const keyArray = key.split('#');
     const pluginName = keyArray.pop();
     const filteredClients = clients.filter(client => {
       // Remove the last entry related to plugin
@@ -94,7 +94,7 @@ export function processNotificationStates(
   allActiveNotifications: Array<PluginNotification>,
   devicePlugins: Map<string, Class<FlipperDevicePlugin<>>>,
 ): Array<PluginNotification> {
-  let activeNotifications = allActiveNotifications.filter(notif => {
+  const activeNotifications = allActiveNotifications.filter(notif => {
     const filteredClients = clients.filter(client =>
       notif.client ? client.id.includes(notif.client) : false,
     );
@@ -176,7 +176,7 @@ export const processStore = async (
   if (device) {
     const {serial} = device;
     const processedClients = processClients(clients, serial);
-    let processedPluginStates = processPluginStates(
+    const processedPluginStates = processPluginStates(
       processedClients,
       serial,
       pluginStates,
@@ -210,7 +210,7 @@ export async function fetchMetadata(
   const errorArray: Array<Error> = [];
   const clients = store.getState().connections.clients;
   const selectedDevice = store.getState().connections.selectedDevice;
-  for (let client of clients) {
+  for (const client of clients) {
     if (
       !selectedDevice ||
       selectedDevice.isArchived ||
@@ -218,7 +218,7 @@ export async function fetchMetadata(
     ) {
       continue;
     }
-    for (let plugin of client.plugins) {
+    for (const plugin of client.plugins) {
       const pluginClass: ?Class<
         FlipperDevicePlugin<> | FlipperPlugin<>,
       > = plugin ? pluginsMap.get(plugin) : null;

src/utils/exportMetrics.js

@@ -22,7 +22,7 @@ async function exportMetrics(
   pluginsMap: Map<string, Class<FlipperDevicePlugin<> | FlipperPlugin<>>>,
 ): Promise<string> {
   const metrics: ExportMetricType = {};
-  for (let key in pluginStates) {
+  for (const key in pluginStates) {
     const pluginStateData = pluginStates[key];
     const arr = key.split('#');
     const pluginName = arr.pop();

src/utils/pluginUtils.js

@@ -46,12 +46,12 @@ export function getPersistedState<PersistedState>(
 }
 
 export function getActivePluginNames(plugins: PluginsState): Array<string> {
-  let pluginsMap: Map<
+  const pluginsMap: Map<
     string,
     Class<FlipperDevicePlugin<> | FlipperPlugin<>>,
   > = pluginsClassMap(plugins);
 
-  let arr: Array<PluginDefinition> = plugins.disabledPlugins.concat(
+  const arr: Array<PluginDefinition> = plugins.disabledPlugins.concat(
     plugins.gatekeepedPlugins,
   );
   arr.forEach((plugin: PluginDefinition) => {

src/utils/promiseTimeout.js

@@ -11,8 +11,8 @@ export default function promiseTimeout<T>(
   timeoutMessage: ?string,
 ): Promise<T> | Promise<void> {
   // Create a promise that rejects in <ms> milliseconds
-  let timeout = new Promise((resolve, reject) => {
+  const timeout = new Promise((resolve, reject) => {
-    let id = setTimeout(() => {
+    const id = setTimeout(() => {
       clearTimeout(id);
       reject(new Error(timeoutMessage || `Timed out in ${ms} ms.`));
     }, ms);

src/utils/serialization.js

@@ -20,7 +20,7 @@ function processArray(
   dict: Map<any, any>,
 ): {childNeedsIteration: boolean, outputArr: Array<any>} {
   // Adds the array item to the stack if it needs to undergo iteration to serialise it. Otherwise it adds the serialized version of the item to the memoization dict
-  let outputArr = [];
+  const outputArr = [];
   let childNeedsIteration = false;
   for (const item of array) {
     const isItemInstanceOfObject = item instanceof Object;
@@ -116,7 +116,7 @@ export function makeObjectSerializable(obj: any): any {
   if (!(obj instanceof Object)) {
     return obj;
   }
-  let stack = [obj];
+  const stack = [obj];
   const dict: Map<any, any> = new Map();
   while (stack.length > 0) {
     const element = stack[stack.length - 1];

static/compilePlugins.js

@@ -39,7 +39,7 @@ module.exports = async (
   }
   watchChanges(plugins, reloadCallback, pluginCache, options);
   const dynamicPlugins = [];
-  for (let plugin of Object.values(plugins)) {
+  for (const plugin of Object.values(plugins)) {
     const dynamicOptions = Object.assign(options, {force: false});
     const compiledPlugin = await compilePlugin(
       plugin,

static/index.js

@@ -66,7 +66,7 @@ const argv = yargs
   .help()
   .parse(process.argv.slice(1));
 
-let {config, configPath, flipperDir} = setup(argv);
+const {config, configPath, flipperDir} = setup(argv);
 
 const pluginPaths = config.pluginPaths
   .concat(

static/transforms/electron-stubs.js

@@ -5,10 +5,10 @@
  * @format
  */
 
-let babylon = require('@babel/parser');
+const babylon = require('@babel/parser');
-let fs = require('fs');
+const fs = require('fs');
 
-let electronStubs = babylon.parseExpression(
+const electronStubs = babylon.parseExpression(
   fs.readFileSync('static/electron-stubs.notjs').toString(),
 );