Support for Dynamic Client Credentials

lib/omniauth/strategies/oauth2.rb

@@ -33,7 +33,15 @@ def self.inherited(subclass)
       attr_accessor :access_token
 
       def client
-        ::OAuth2::Client.new(options.client_id, options.client_secret, deep_symbolize(options.client_options))
+        ::OAuth2::Client.new(client_id, client_secret, deep_symbolize(options.client_options))
+      end
+
+      def client_id
+        options.client_id.respond_to?(:call) ? options.client_id.call : options.client_id
+      end
+
+      def client_secret
+        options.client_secret.respond_to?(:call) ? options.client_secret.call : options.client_secret
       end
 
       def callback_url

spec/omniauth/strategies/oauth2_spec.rb

@@ -37,6 +37,18 @@ def app
       instance = subject.new(app, :client_options => {"ssl" => {"ca_path" => "foo"}})
       expect(instance.client.options[:connection_opts][:ssl]).to eq(:ca_path => "foo")
     end
+
+    it "allows client_id to be passed as a lambda function" do
+      client_id = proc { "abc" }
+      instance = subject.new(Object, client_id, "def")
+      expect(instance.client.id).to eq("abc")
+    end
+
+    it "allows client_secret to be passed as a lambda function" do
+      client_secret = proc { "def" }
+      instance = subject.new(Object, "abc", client_secret)
+      expect(instance.client.secret).to eq("def")
+    end
   end
 
   describe "#authorize_params" do