fix: regression from #272

lib/client.js

@@ -1594,10 +1594,11 @@ BaseClient.prototype.resource = deprecate(
   /* istanbul ignore next */
   async function resource(resourceUrl, accessToken, options) {
     let token = accessToken;
-    const opts = defaultsDeep({}, options, {
+    const opts = {
       verb: 'GET',
       via: 'header',
-    });
+      ...options,
+    };
 
     if (token instanceof TokenSet) {
       if (!token.access_token) {

lib/helpers/client.js

@@ -5,7 +5,7 @@ const { random } = require('./generators');
 const now = require('./unix_timestamp');
 const request = require('./request');
 const instance = require('./weak_cache');
-const { deep: defaultsDeep } = require('./defaults');
+const merge = require('./merge');
 
 const formUrlEncode = (value) => encodeURIComponent(value).replace(/%20/g, '+');
 
@@ -125,7 +125,7 @@ async function authenticatedPost(endpoint, opts, {
   clientAssertionPayload, endpointAuthMethod = endpoint,
 } = {}) {
   const auth = await authFor.call(this, endpointAuthMethod, { clientAssertionPayload });
-  const requestOpts = defaultsDeep({ form: true }, auth, opts);
+  const requestOpts = merge(opts, auth, { form: true });
 
   const mTLS = this[`${endpointAuthMethod}_endpoint_auth_method`].includes('tls_client_auth')
     || (endpoint === 'token' && this.tls_client_certificate_bound_access_tokens);

lib/helpers/merge.js

@@ -0,0 +1,23 @@
+/* eslint-disable no-restricted-syntax */
+
+const isPlainObject = require('./is_plain_object');
+
+function merge(...sources) {
+  const target = {};
+  for (const source of sources) {
+    if (!isPlainObject(source)) {
+      continue; // eslint-disable-line no-continue
+    }
+    for (const [key, value] of Object.entries(source)) {
+      if (isPlainObject(target[key]) && isPlainObject(value)) {
+        target[key] = merge(target[key], value);
+      } else if (typeof value !== 'undefined') {
+        target[key] = value;
+      }
+    }
+  }
+
+  return target;
+}
+
+module.exports = merge.bind(undefined, false);