Forward the env to Request::Authorization#header_from

docs/middleware/request/authentication.md

@@ -30,6 +30,14 @@ Faraday.new(...) do |conn|
 end
 ```
 
+If the proc takes an argument, it will receive the forwarded `env`
+
+```ruby
+Faraday.new(...) do |conn|
+  conn.request :authorization, 'Bearer', ->(env) { MyAuthStorage.get_auth_token(env) }
+end
+```
+
 ### Basic Authentication
 
 The middleware will automatically Base64 encode your Basic username and password:

lib/faraday/request/authorization.rb

@@ -23,22 +23,27 @@ def initialize(app, type, *params)
       def on_request(env)
         return if env.request_headers[KEY]
 
-        env.request_headers[KEY] = header_from(@type, *@params)
+        env.request_headers[KEY] = header_from(@type, env, *@params)
       end
 
       private
 
       # @param type [String, Symbol]
+      # @param env [Faraday::Env]
       # @param params [Array]
       # @return [String] a header value
-      def header_from(type, *params)
+      def header_from(type, env, *params)
         if type.to_s.casecmp('basic').zero? && params.size == 2
           Utils.basic_header_from(*params)
         elsif params.size != 1
           raise ArgumentError, "Unexpected params received (got #{params.size} instead of 1)"
         else
           value = params.first
-          value = value.call if value.is_a?(Proc) || value.respond_to?(:call)
+          if (value.is_a?(Proc) && value.arity == 1) || (value.respond_to?(:call) && value.method(:call).arity == 1)
+            value = value.call(env)
+          elsif value.is_a?(Proc) || value.respond_to?(:call)
+            value = value.call
+          end
           "#{type} #{value}"
         end
       end

spec/faraday/request/authorization_spec.rb

@@ -72,6 +72,41 @@
       include_examples 'does not interfere with existing authentication'
     end
 
+    context 'with an argument' do
+      let(:response) { conn.get('/auth-echo', nil, 'middle' => 'crunchy surprise') }
+
+      context 'when passed a proc' do
+        let(:auth_config) { [proc { |env| "proc #{env.request_headers['middle']}" }] }
+
+        it { expect(response.body).to eq('Bearer proc crunchy surprise') }
+
+        include_examples 'does not interfere with existing authentication'
+      end
+
+      context 'when passed a lambda' do
+        let(:auth_config) { [->(env) { "lambda #{env.request_headers['middle']}" }] }
+
+        it { expect(response.body).to eq('Bearer lambda crunchy surprise') }
+
+        include_examples 'does not interfere with existing authentication'
+      end
+
+      context 'when passed a callable with an argument' do
+        let(:callable) do
+          Class.new do
+            def call(env)
+              "callable #{env.request_headers['middle']}"
+            end
+          end.new
+        end
+        let(:auth_config) { [callable] }
+
+        it { expect(response.body).to eq('Bearer callable crunchy surprise') }
+
+        include_examples 'does not interfere with existing authentication'
+      end
+    end
+
     context 'when passed too many arguments' do
       let(:auth_config) { %w[baz foo] }