fix: Accept undefined pluginConfig

lib/index.js

@@ -15,7 +15,7 @@ const DEFAULT_RELEASE_RULES = require('./default/release-rules');
 /**
  * Determine the type of release to create based on a list of commits.
  *
- * @param {Object} pluginConfig semantic-release configuration
+ * @param {Object} [pluginConfig={}] semantic-release configuration
  * @param {string} pluginConfig.preset conventional-changelog preset ('angular', 'atom', 'codemirror', 'ember', 'eslint', 'express', 'jquery', 'jscs', 'jshint')
  * @param {string} pluginConfig.config requierable npm package with a custom conventional-changelog preset
  * @param {string|Array} pluginConfig.releaseRules a string to load an external module or an `Array` of rules.
@@ -24,7 +24,7 @@ const DEFAULT_RELEASE_RULES = require('./default/release-rules');
  * @param {Array} options.commits array of commits
  * @param {commitAnalyzerCallback} callback The callback called with the release type.
  */
-module.exports = async (pluginConfig, {commits}, callback) => {
+module.exports = async (pluginConfig = {}, {commits}, callback) => {
   try {
     const releaseRules = loadReleaseRules(pluginConfig);
     const config = await loadParserConfig(pluginConfig);

test/integration.test.js

@@ -187,3 +187,10 @@ test('Handle error in "conventional-changelog-parser" and wrap in "SemanticRelea
 
   t.true(error instanceof SemanticReleaseError);
 });
+
+test('Accept an undefined "pluginConfig"', async t => {
+  const commits = [{message: 'fix(scope1): First fix'}, {message: 'feat(scope2): Second feature'}];
+  const releaseType = await pify(commitAnalyzer)(undefined, {commits});
+
+  t.is(releaseType, 'minor');
+});