Add eslint for linting

PR-URL: #748
Credit: @jsumners
Close: #748
Reviewed-by: @isaacs

EDIT(@isaacs): move lint to postsnap, and do --fix by default.  We
always have to run snapshots before pushing a new version, and expect to
get code changes as a result.  This is much more convenient than having
tests just not run becuase of some scaffolding or something.

.eslintrc.js

@@ -0,0 +1,15 @@
+module.exports = {
+  extends: 'eslint:recommended',
+
+  env: {
+    node: true,
+    es2020: true
+  },
+
+  rules: {
+    'no-prototype-builtins': 'off',
+    'no-empty': 'off',
+    'no-regex-spaces': 'off',
+    'no-useless-escape': 'off'
+  }
+}

.gitignore

@@ -25,3 +25,4 @@
 !coverage-map.js
 !postpublish.sh
 !netlify.toml
+!.eslintrc.js

bin/jack.js

@@ -6,7 +6,6 @@ const reporters = [...new Set([
   ...(require('tap-mocha-reporter').types),
   ...(require('treport/types')),
 ])]
-const fs = require('fs')
 // nyc bundles its deps, pull reporters out of it
 const nycReporters = [
   'clover',
@@ -693,6 +692,7 @@ Much more documentation available at: https://www.node-tap.org/
                   appended to the filenames.`,
   }),
 
+  /* eslint-disable-next-line */
   debug: flag({
     envDefault: 'TAP_DEBUG',
     description: 'Turn on debug mode',

bin/run.js

@@ -20,7 +20,6 @@ const isexe = require('isexe')
 const yaml = require('tap-yaml')
 const path = require('path')
 const exists = require('fs-exists-cached').sync
-const os = require('os')
 
 const maybeResolve = id => {
   try {
@@ -358,7 +357,7 @@ const runCoverageReportOnly = options => {
 }
 
 /* istanbul ignore next */
-const pipeToCoveralls = async options => {
+const pipeToCoveralls = async () => {
   const reporter = spawn(node, [nycBin, 'report', '--reporter=text-lcov'], {
     stdio: [ 0, 'pipe', 2 ]
   })
@@ -398,7 +397,7 @@ const openHtmlCoverageReport = (options, code, signal) => {
   }
 }
 
-const nycHelp = _ => fg(node, [nycBin, '--help'])
+const nycHelp = () => fg(node, [nycBin, '--help'])
 
 // export for easier testing
 const setupTapEnv = exports.setupTapEnv = options => {
@@ -536,7 +535,7 @@ const saveFails = (options, tap) => {
       } catch (er) {}
   }
 
-  tap.on('bailout', reason => {
+  tap.on('bailout', () => {
     // add any pending test files to the fails list.
     fails.push.apply(fails, options.files.filter(file =>
       successes.indexOf(file) === -1))

lib/mocha.js

@@ -2,7 +2,6 @@
 const t = require('./tap.js')
 t.jobs = 1
 const tapStack = [ t ]
-let level = 0
 const suiteStack = []
 
 const describe = (name, fn, opt) =>
@@ -83,7 +82,6 @@ const it = (name, fn, options) => {
     name = fn.name
   options = options || {}
   const todo = !fn
-  const suite = suiteStack[ suiteStack.length - 1 ]
   const t = tapStack[ tapStack.length - 1 ]
   if (!name)
     name = ''
@@ -119,7 +117,6 @@ function moment (when, fn) {
   t[when](function () {
     if (!this.options.tapMochaTest)
       return
-    const suite = suiteStack[ suiteStack.length - 1 ]
 
     const [cb, p] = cbPromise()
     const ret = fn.call(this, cb)
@@ -144,7 +141,7 @@ exports.beforeEach = beforeEach
 exports.afterEach = afterEach
 
 let saved
-exports.global = _ => {
+exports.global = () => {
   if (!saved)
     saved = new Map()
 
@@ -155,7 +152,7 @@ exports.global = _ => {
   })
 }
 
-exports.deglobal = _ =>
+exports.deglobal = () =>
   Object.keys(exports).filter(g => g !== 'global').forEach(g => {
     if (saved && saved.has(g))
       global[g] = saved.get(g)

lib/repl.js

@@ -186,7 +186,7 @@ class Repl {
     this.run(null, cb)
   }
 
-  exit (cb) {
+  exit () {
     this.watch.pause()
     this.watch.kill('SIGTERM')
     this.repl.close()

lib/tap.js

@@ -1,6 +1,6 @@
 'use strict'
 const {deprecate} = require('util')
-const settings = require('../settings.js')
+require('../settings.js')
 const tap = require('libtap')
 
 // Needs to be set before requiring mocha.js

lib/watch.js

@@ -1,12 +1,12 @@
 const proc = typeof process === 'object' && process ? process : null
 
 const chokidar = require('chokidar')
-const EE = require('events')
 const Minipass = require('minipass')
 const bin = require.resolve('../bin/run.js')
 const {spawn} = require('child_process')
 const onExit = require('signal-exit')
-const {writeFileSync, readFileSync} = require('fs')
+const fs = require('fs')
+const {writeFileSync, readFileSync} = fs
 const {stringify} = require('tap-yaml')
 const {resolve} = require('path')
 
@@ -55,7 +55,6 @@ class Watch extends Minipass {
     // Since a covered test was definitely included in its own
     // test run, don't add it a second time, so we don't get
     // two chokidar events for the same file change.
-    const cwd = proc.cwd()
     const fileSet = new Set(Object.keys(this.index.files))
     Object.keys(this.index.externalIds)
       .filter(f => !fileSet.has(resolve(f)))
@@ -107,7 +106,7 @@ class Watch extends Minipass {
     this.run()
   }
 
-  run (env) {
+  run () {
     const set = [...new Set(this.queue)]
     this.log('running tests', set)
     writeFileSync(this.saveFile, set.join('\n') + '\n')
@@ -140,7 +139,7 @@ class Watch extends Minipass {
     // then add those, but ignore if it's not there.
     const leftover = (() => {
       try {
-        return fs.readFileSync(saveFile, 'utf8').trim().split('\n')
+        return fs.readFileSync(this.saveFile, 'utf8').trim().split('\n')
       } catch (er) {
         return []
       }