Callable authorizers

lib/faraday/request/authorization.rb

@@ -8,10 +8,11 @@ class Authorization < Faraday::Middleware
 
       # @param app [#call]
       # @param type [String, Symbol] Type of Authorization
-      # @param params [Array<String, Proc>] parameters to build the Authorization header.
+      # @param params [Array<String, Proc, #call>] parameters to build the Authorization header.
       #   If the type is `:basic`, then these can be a login and password pair.
       #   Otherwise, a single value is expected that will be appended after the type.
-      #   This value can be a proc, in which case it will be invoked on each request.
+      #   This value can be a proc or an object responding to `.call`, in which case
+      #   it will be invoked on each request.
       def initialize(app, type, *params)
         @type = type
         @params = params
@@ -37,7 +38,7 @@ def header_from(type, *params)
           raise ArgumentError, "Unexpected params received (got #{params.size} instead of 1)"
         else
           value = params.first
-          value = value.call if value.is_a?(Proc)
+          value = value.call if value.is_a?(Proc) || value.respond_to?(:call)
           "#{type} #{value}"
         end
       end

spec/faraday/request/authorization_spec.rb

@@ -63,6 +63,15 @@
       include_examples 'does not interfere with existing authentication'
     end
 
+    context 'when passed a callable' do
+      let(:callable) { double('Callable Authorizer', call: 'custom_from_callable') }
+      let(:auth_config) { [callable] }
+
+      it { expect(response.body).to eq('Bearer custom_from_callable') }
+
+      include_examples 'does not interfere with existing authentication'
+    end
+
     context 'when passed too many arguments' do
       let(:auth_config) { %w[baz foo] }