FEATURE: Fetch custom attributes from the user details. (#47)

Other plugins can tell the authenticator to traverse the user details JSON using custom paths and store the values in the user associated account extra field.

plugin.rb

@@ -71,6 +71,10 @@ class OAuth2FaradayFormatter < Faraday::Logging::Formatter
   end
 end
 
+# You should use this register if you want to add custom paths to traverse the user details JSON.
+# We'll store the value in the user associated account's extra attribute hash using the full path as the key.
+DiscoursePluginRegistry.define_filtered_register :oauth2_basic_additional_json_paths
+
 class ::OAuth2BasicAuthenticator < Auth::ManagedAuthenticator
   def name
     'oauth2_basic'
@@ -164,8 +168,8 @@ class ::OAuth2BasicAuthenticator < Auth::ManagedAuthenticator
     end
   end
 
-  def json_walk(result, user_json, prop)
-    path = SiteSetting.public_send("oauth2_json_#{prop}_path")
+  def json_walk(result, user_json, prop, custom_path: nil)
+    path = custom_path || SiteSetting.public_send("oauth2_json_#{prop}_path")
     if path.present?
       #this.[].that is the same as this.that, allows for both this[0].that and this.[0].that path styles
       path = path.gsub(".[].", ".").gsub(".[", "[")
@@ -229,6 +233,11 @@ class ::OAuth2BasicAuthenticator < Auth::ManagedAuthenticator
         json_walk(result, user_json, :email)
         json_walk(result, user_json, :email_verified)
         json_walk(result, user_json, :avatar)
+
+        DiscoursePluginRegistry.oauth2_basic_additional_json_paths.each do |detail|
+          prop = "extra:#{detail}"
+          json_walk(result, user_json, prop, custom_path: detail)
+        end
       end
       result
     else
@@ -259,6 +268,10 @@ class ::OAuth2BasicAuthenticator < Auth::ManagedAuthenticator
         ['name', 'email', 'email_verified'].each do |property|
           auth['info'][property] = fetched_user_details[property.to_sym] if fetched_user_details[property.to_sym]
         end
+
+        DiscoursePluginRegistry.oauth2_basic_additional_json_paths.each do |detail|
+          auth['extra'][detail] = fetched_user_details["extra:#{detail}"]
+        end
       else
         result = Auth::Result.new
         result.failed = true

spec/plugin_spec.rb

@@ -122,6 +122,31 @@ describe OAuth2BasicAuthenticator do
         result = authenticator.after_authenticate(auth)
         expect(result.failed).to eq(true)
       end
+
+      describe 'fetch custom attributes' do
+        after { DiscoursePluginRegistry.reset! }
+
+        let(:response) do
+          {
+            status: 200,
+            body: '{"account":{"email":"newemail@example.com","custom_attr":"received"}}'
+          }
+        end
+
+        it 'stores custom attributes in the user associated account' do
+          custom_path = 'account.custom_attr'
+          DiscoursePluginRegistry.register_oauth2_basic_additional_json_path(
+            custom_path,
+            Plugin::Instance.new
+          )
+          stub_request(:get, SiteSetting.oauth2_user_json_url).to_return(response)
+
+          result = authenticator.after_authenticate(auth)
+          associated_account = UserAssociatedAccount.last
+
+          expect(associated_account.extra[custom_path]).to eq("received")
+        end
+      end
     end
 
     context 'avatar downloading' do