Add a function to merge user specified dependencies into default dependencies

Based on electron-userland/electron-installer-redhat#98

Author: malept

src/dependencies.js

@@ -1,5 +1,6 @@
 'use strict'
 
+const _ = require('lodash')
 const semver = require('semver')
 
 /**
@@ -56,5 +57,23 @@ module.exports = {
   getGConfDepends: getGConfDepends,
   getGTKDepends: getGTKDepends,
   getTrashDepends: getTrashDepends,
-  getUUIDDepends: getUUIDDepends
+  getUUIDDepends: getUUIDDepends,
+
+  /**
+   * Merge the user specified dependencies (from either the API or the CLI) with the respective
+   * default dependencies, given the `dependencyKey`.
+   *
+   * @param {object} data - the user-specified data
+   * @param {string} dependencyKey - the dependency type (e.g., `depends` for Debian
+   * runtime dependencies)
+   * @param {object} defaults - the default options for the installer module
+   *
+   */
+  mergeUserSpecified: function mergeUserSpecified (data, dependencyKey, defaults) {
+    if (data.options) { // options passed programmatically
+      return _.union(defaults[dependencyKey], data.options[dependencyKey])
+    } else { // options passed via command-line
+      return _.union(defaults[dependencyKey], data[dependencyKey])
+    }
+  }
 }

test/dependencies.js

@@ -1,5 +1,6 @@
 'use strict'
 
+const _ = require('lodash')
 const dependencies = require('../src/dependencies')
 const test = require('ava')
 
@@ -68,3 +69,22 @@ test('getUUIDDepends: returns nothing pre-4.0', t => {
 test('getUUIDDepends: returns uuid as of 4.0', t => {
   t.is(dependencies.getUUIDDepends('4.0.0', dependencyMap)[0], dependencyMap.uuid)
 })
+
+function testMergeUserSpecified (t, dataPath) {
+  const defaults = {
+    dependencies: ['lsb', 'libXScrnSaver']
+  }
+  const data = _.set({}, dataPath, ['dbus', 'dbus', 'lsb'])
+
+  const actual = dependencies.mergeUserSpecified(data, 'dependencies', defaults)
+  actual.sort()
+  t.deepEqual(actual, ['dbus', 'libXScrnSaver', 'lsb'])
+}
+
+test('mergeUserSpecified with API options', t => {
+  testMergeUserSpecified(t, 'options.dependencies')
+})
+
+test('mergeUserSpecified with CLI options', t => {
+  testMergeUserSpecified(t, 'dependencies')
+})