Refactor error suppression using custom errors

Prefer checking errors by name than by message.

init.js

@@ -6,12 +6,7 @@ const minimatch = require('minimatch')
 const { relative } = require('path')
 
 function suppressError (err) {
-  return [
-    'no supported linter found',
-    'no package.json found'
-  ].some(pattern => {
-    return pattern === err.message
-  })
+  return err.name === 'MissingLinterError' || err.name === 'MissingPackageError'
 }
 
 function lint (textEditor) {

lib/findOptions.js

@@ -1,11 +1,24 @@
 const { dirname } = require('path')
+const ExtendableError = require('es6-error')
 const readPkgUp = require('read-pkg-up')
 const supportedLinters = require('./supportedLinters')
 
+class MissingLinterError extends ExtendableError {
+  constructor (message = 'no supported linter found') {
+    super(message)
+  }
+}
+
+class MissingPackageError extends ExtendableError {
+  constructor (message = 'no package.json found') {
+    super(message)
+  }
+}
+
 function findOptions (file) {
   return readPkgUp({ cwd: dirname(file) })
     .then(({ path, pkg }) => {
-      if (!pkg) throw new Error('no package.json found')
+      if (!pkg) throw new MissingPackageError()
 
       let linters = []
       if (pkg.devDependencies) {
@@ -20,7 +33,7 @@ function findOptions (file) {
       }
 
       if (linters.length === 0) {
-        throw new Error('no supported linter found')
+        throw new MissingLinterError()
       }
 
       const linterName = linters[0]
@@ -43,4 +56,7 @@ function findOptions (file) {
     })
 }
 
-module.exports = findOptions
+exports = module.exports = findOptions
+
+exports.MissingLinterError = MissingLinterError
+exports.MissingPackageError = MissingPackageError

package.json

@@ -48,6 +48,7 @@
     }
   },
   "dependencies": {
+    "es6-error": "^4.0.1",
     "lru-cache": "^4.0.1",
     "minimatch": "^3.0.3",
     "read-pkg-up": "^2.0.0",

test/init.spec.js

@@ -6,6 +6,7 @@ const proxyquire = require('proxyquire')
 const fs = require('fs')
 const path = require('path')
 const plugin = require('../init')
+const { MissingLinterError, MissingPackageError } = require('../lib/findOptions')
 const textEditorFactory = require('./util/textEditorFactory')
 const linter = plugin.provideLinter()
 const lint = linter.lint.bind(linter)
@@ -66,12 +67,9 @@ describe('linter-js-standard-engine', () => {
       }
     }).provideLinter()
 
-    for (const msg of [
-      'no supported linter found',
-      'no package.json found'
-    ]) {
-      it(`should suppress "${msg}" errors`, () => {
-        currentError = new Error(msg)
+    for (const ErrorClass of [MissingLinterError, MissingPackageError]) {
+      it(`should suppress "${ErrorClass.name}" errors`, () => {
+        currentError = new ErrorClass()
         return expect(linter.lint(textEditorFactory('')), 'to be fulfilled').then(data => expect(data, 'to be empty'))
       })
     }