feat: Add the 'Preferred-Languages' directive (#53)

The preferredLanguages key implements the Preferred-Languages directive. It can be passed a comma delimited string, or an array that will be converted into one.

#50

__tests__/formatPolicy.test.js

@@ -153,3 +153,31 @@ test('uses new spelling with deprecated keys', () => {
 
   expect(global.console.warn).toHaveBeenCalled()
 })
+
+test('preferredLanguages directive works with multiple values', () => {
+  const options = {
+    contact: 'mailto:[email protected]',
+    preferredLanguages: ['en', 'ru', 'es']
+  }
+
+  const res = securityTxt.formatSecurityPolicy(options)
+
+  expect(res).toBe(
+    'Contact: mailto:[email protected]\n' +
+    'Preferred-Languages: en, ru, es\n'
+  )
+})
+
+test('preferredLanguages directive works with one value only', () => {
+  const options = {
+    contact: 'mailto:[email protected]',
+    preferredLanguages: 'en'
+  }
+
+  const res = securityTxt.formatSecurityPolicy(options)
+
+  expect(res).toBe(
+    'Contact: mailto:[email protected]\n' +
+    'Preferred-Languages: en\n'
+  )
+})

__tests__/validatePolicy.test.js

@@ -217,3 +217,35 @@ test('using both deprecated spelling and new spelling throws', () => {
 
   expect(() => securityTxt.validatePolicyFields(options)).toThrow()
 })
+
+test('validate successfully for the preferredLanguages key', () => {
+  const optionsWithArray = {
+    contact: '...',
+    preferredLanguages: ['en', 'es']
+  }
+
+  const optionsWithString = {
+    contact: '...',
+    preferredLanguages: 'ru'
+  }
+
+  const optionsWithComment = {
+    contact: '...',
+    preferredLanguages: { comment: 'I am fluent in these', value: ['en', 'ru'] }
+  }
+
+  expect(() => securityTxt.validatePolicyFields(optionsWithArray)).not.toThrow()
+  expect(() => securityTxt.validatePolicyFields(optionsWithString)).not.toThrow()
+  expect(() => securityTxt.validatePolicyFields(optionsWithComment)).not.toThrow()
+})
+
+test('validate fails if Array<object> fed to preferredLanguages', () => {
+  const options = {
+    contact: '...',
+    preferredLanguages: [
+      { comment: '...', value: 'en' }
+    ]
+  }
+
+  expect(() => securityTxt.validatePolicyFields(options).toThrow())
+})

index.js

@@ -1,7 +1,7 @@
 'use strict'
 
 const Joi = require('joi')
-const DIRECTIVES = ['Contact', 'Encryption', 'Acknowledgments', 'Signature', 'Policy', 'Hiring', 'Permission']
+const DIRECTIVES = ['Contact', 'Encryption', 'Acknowledgments', 'Preferred-Languages', 'Signature', 'Policy', 'Hiring', 'Permission']
 
 /**
  * @TODO Fully remove outdated spelling in breaking changes
@@ -104,6 +104,14 @@ class middleware {
         value = [ value ]
       }
 
+      // For the other fields, arrays are used to represent multiple occurences
+      // of a field. However, for the Preferred-Language: directive, an array shows
+      // a comma separated list. Convert the provided array into an array of one
+      // value: a string with commas.
+      if (outputDirective === 'Preferred-Languages') {
+        value = [ value.map(languageCode => languageCode.trim()).join(', ') ]
+      }
+
       value.forEach(valueOption => {
         if (valueOption.hasOwnProperty('value')) {
           if (valueOption.hasOwnProperty('comment')) {
@@ -187,6 +195,7 @@ class middleware {
       contact: fieldValue({ required: true }),
       permission: fieldValue({ canBeArray: false, singleValue: string.only('none').insensitive() }),
       encryption: fieldValue({ singleValue: string.regex(/^(?!http:)/i) }),
+      preferredLanguages: fieldValue({ canBeArray: false, singleValue: array.items(string) }),
       policy: fieldValue(),
       hiring: fieldValue(),
       signature: fieldValue({ canBeArray: false }),