Implement support for parsing error responses.

lib/strategy.js

@@ -7,6 +7,7 @@ var passport = require('passport-strategy')
   , utils = require('./utils')
   , OAuth2 = require('oauth').OAuth2
   , AuthorizationError = require('./errors/authorizationerror')
+  , AccessTokenError = require('./errors/accesstokenerror')
   , InternalOAuthError = require('./errors/internaloautherror');
 
 
@@ -144,7 +145,7 @@ OAuth2Strategy.prototype.authenticate = function(req, options) {
     //       presence does not appear to cause any issues.
     this._oauth2.getOAuthAccessToken(code, { grant_type: 'authorization_code', redirect_uri: callbackURL },
       function(err, accessToken, refreshToken, params) {
-        if (err) { return self.error(new InternalOAuthError('Failed to obtain access token', err)); }
+        if (err) { return self.error(self._createOAuthError('Failed to obtain access token', err)); }
 
         self._loadUserProfile(accessToken, function(err, profile) {
           if (err) { return self.error(err); }
@@ -229,6 +230,29 @@ OAuth2Strategy.prototype.authorizationParams = function(options) {
   return {};
 };
 
+/**
+ * Parse error response from OAuth 2.0 endpoint.
+ *
+ * OAuth 2.0-based authentication strategies can overrride this function in
+ * order to parse error responses received from the token endpoint, allowing the
+ * most informative message to be displayed.
+ *
+ * If this function is not overridden, the body will be parsed in accordance
+ * with RFC 6749, section 5.2.
+ *
+ * @param {String} body
+ * @param {Number} status
+ * @return {Error}
+ * @api protected
+ */
+OAuth2Strategy.prototype.parseErrorResponse = function(body, status) {
+  var json = JSON.parse(body);
+  if (json.error) {
+    return new AccessTokenError(json.error_description, json.error, json.error_uri)
+  }
+  return null;
+};
+
 /**
  * Load user profile, contingent upon options.
  *
@@ -260,6 +284,24 @@ OAuth2Strategy.prototype._loadUserProfile = function(accessToken, done) {
   }
 };
 
+/**
+ * Create an OAuth error.
+ *
+ * @param {String} message
+ * @param {Object|Error} err
+ * @api private
+ */
+OAuth2Strategy.prototype._createOAuthError = function(message, err) {
+  var e;
+  if (err.statusCode && err.data) {
+    try {
+      e = this.parseErrorResponse(err.data, err.statusCode);
+    } catch (_) {}
+  }
+  if (!e) { e = new InternalOAuthError(message, err); }
+  return e;
+};
+
 
 /**
  * Expose `OAuth2Strategy`.