Add order/position test.

extension/awsmiddleware/README.md

@@ -0,0 +1,29 @@
+# AWS Middleware
+
+An AWS middleware extension provides request and/or response handlers that can be configured on AWS SDK v1/v2 clients.
+Other components can configure their AWS SDK clients using the `awsmiddleware.ConfigureSDKv1` and `awsmiddleware.ConfigureSDKv2` functions.
+
+The `awsmiddleware.Extension` interface extends `component.Extension` by adding the following methods:
+```
+RequestHandlers() []RequestHandler
+ResponseHandlers() []ResponseHandler
+```
+
+The `awsmiddleware.RequestHandler` interface contains the following methods:
+```
+ID() string
+Position() HandlerPosition
+HandleRequest(r *http.Request)
+```
+
+The `awsmiddleware.ResponseHandler` interface contains the following methods:
+```
+ID() string
+Position() HandlerPosition
+HandleResponse(r *http.Response)
+```
+
+- `ID` uniquely identifies a handler. Middleware will fail if there is clashing 
+- `Position` determines whether the handler is appended to the front or back of the existing list. Insertion is done
+in the order of the handlers provided.
+- `HandleRequest/Response` provides a hook to handle the request/response before and after they've been sent.

extension/awsmiddleware/middleware.go

@@ -49,8 +49,8 @@ func (h HandlerPosition) String() string {
 	}
 }
 
-// MarshalText converts the position into a string. Returns an error
-// if unsupported.
+// MarshalText converts the position into a byte slice.
+// Returns an error if unsupported.
 func (h HandlerPosition) MarshalText() (text []byte, err error) {
 	s := h.String()
 	if s == "" {
@@ -73,9 +73,9 @@ func (h *HandlerPosition) UnmarshalText(text []byte) error {
 	return nil
 }
 
-// metadata is used to differentiate between handlers and determine
+// handlerConfig is used to differentiate between handlers and determine
 // relative positioning within their groups.
-type metadata interface {
+type handlerConfig interface {
 	// ID must be unique. It cannot clash with existing middleware.
 	ID() string
 	// Position to insert the handler.
@@ -84,13 +84,13 @@ type metadata interface {
 
 // RequestHandler allows for custom processing of requests.
 type RequestHandler interface {
-	metadata
+	handlerConfig
 	HandleRequest(r *http.Request)
 }
 
 // ResponseHandler allows for custom processing of responses.
 type ResponseHandler interface {
-	metadata
+	handlerConfig
 	HandleResponse(r *http.Response)
 }
 
@@ -112,12 +112,12 @@ type Extension interface {
 func ConfigureSDKv1(mw Middleware, handlers *request.Handlers) error {
 	var errs error
 	for _, handler := range mw.RequestHandlers() {
-		if err := addHandlerToList(&handlers.Build, namedRequestHandler(handler), handler.Position()); err != nil {
+		if err := appendHandler(&handlers.Build, namedRequestHandler(handler), handler.Position()); err != nil {
 			errs = errors.Join(errs, fmt.Errorf("%w (%q): %w", errInvalidHandler, handler.ID(), err))
 		}
 	}
 	for _, handler := range mw.ResponseHandlers() {
-		if err := addHandlerToList(&handlers.Unmarshal, namedResponseHandler(handler), handler.Position()); err != nil {
+		if err := appendHandler(&handlers.Unmarshal, namedResponseHandler(handler), handler.Position()); err != nil {
 			errs = errors.Join(errs, fmt.Errorf("%w (%q): %w", errInvalidHandler, handler.ID(), err))
 		}
 	}
@@ -134,27 +134,21 @@ func ConfigureSDKv2(mw Middleware, config *aws.Config) error {
 			errs = errors.Join(errs, fmt.Errorf("%w (%q): %w", errInvalidHandler, handler.ID(), err))
 			continue
 		}
-		rmw := &requestMiddleware{RequestHandler: handler, position: relativePosition}
-		config.APIOptions = append(config.APIOptions, func(stack *middleware.Stack) error {
-			return stack.Build.Add(rmw, rmw.position)
-		})
+		config.APIOptions = append(config.APIOptions, withBuildOption(&requestMiddleware{RequestHandler: handler}, relativePosition))
 	}
 	for _, handler := range mw.ResponseHandlers() {
 		relativePosition, err := toRelativePosition(handler.Position())
 		if err != nil {
 			errs = errors.Join(errs, fmt.Errorf("%w (%q): %w", errInvalidHandler, handler.ID(), err))
 			continue
 		}
-		rmw := &responseMiddleware{ResponseHandler: handler, position: relativePosition}
-		config.APIOptions = append(config.APIOptions, func(stack *middleware.Stack) error {
-			return stack.Deserialize.Add(rmw, rmw.position)
-		})
+		config.APIOptions = append(config.APIOptions, withDeserializeOption(&responseMiddleware{ResponseHandler: handler}, relativePosition))
 	}
 	return errs
 }
 
 // addHandlerToList adds the handler to the list based on the position.
-func addHandlerToList(handlerList *request.HandlerList, handler request.NamedHandler, position HandlerPosition) error {
+func appendHandler(handlerList *request.HandlerList, handler request.NamedHandler, position HandlerPosition) error {
 	relativePosition, err := toRelativePosition(position)
 	if err != nil {
 		return err

extension/awsmiddleware/middleware_test.go

@@ -63,6 +63,16 @@ func (t *testHandler) Latency() time.Duration {
 	return t.end.Sub(t.start)
 }
 
+type recordOrder struct {
+	order []string
+}
+
+func (ro *recordOrder) handle(id string) func(*http.Request) {
+	return func(*http.Request) {
+		ro.order = append(ro.order, id)
+	}
+}
+
 func TestHandlerPosition(t *testing.T) {
 	testCases := []struct {
 		position HandlerPosition
@@ -111,8 +121,80 @@ func TestInvalidHandlers(t *testing.T) {
 	assert.True(t, errors.Is(err, errUnsupportedPosition))
 }
 
+func TestAppendOrder(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer server.Close()
+	testCases := map[string]struct {
+		requestHandlers []*testHandler
+		wantOrder       []string
+	}{
+		"WithBothBefore": {
+			requestHandlers: []*testHandler{
+				{id: "1", position: Before},
+				{id: "2", position: Before},
+			},
+			wantOrder: []string{"2", "1"},
+		},
+		"WithBothAfter": {
+			requestHandlers: []*testHandler{
+				{id: "1", position: After},
+				{id: "2", position: After},
+			},
+			wantOrder: []string{"1", "2"},
+		},
+		"WithBeforeAfter": {
+			requestHandlers: []*testHandler{
+				{id: "1", position: Before},
+				{id: "2", position: After},
+			},
+			wantOrder: []string{"1", "2"},
+		},
+		"WithAfterBefore": {
+			requestHandlers: []*testHandler{
+				{id: "1", position: After},
+				{id: "2", position: Before},
+			},
+			wantOrder: []string{"2", "1"},
+		},
+	}
+	for name, testCase := range testCases {
+		t.Run(name, func(t *testing.T) {
+			middleware := &testMiddlewareExtension{}
+			recorder := &recordOrder{}
+			for _, handler := range testCase.requestHandlers {
+				handler.handleRequest = recorder.handle(handler.id)
+				middleware.requestHandlers = append(middleware.requestHandlers, handler)
+			}
+			// v1
+			client := awstesting.NewClient(&awsv1.Config{
+				Region:     awsv1.String("mock-region"),
+				DisableSSL: awsv1.Bool(true),
+				Endpoint:   awsv1.String(server.URL),
+			})
+			assert.NoError(t, ConfigureSDKv1(middleware, &client.Handlers))
+			s3v1Client := &s3v1.S3{Client: client}
+			_, err := s3v1Client.ListBuckets(&s3v1.ListBucketsInput{})
+			require.NoError(t, err)
+			assert.Equal(t, testCase.wantOrder, recorder.order)
+			recorder.order = nil
+			// v2
+			cfg := awsv2.Config{Region: "us-east-1"}
+			assert.NoError(t, ConfigureSDKv2(middleware, &cfg))
+			s3v2Client := s3v2.NewFromConfig(cfg, func(options *s3v2.Options) {
+				options.BaseEndpoint = awsv2.String(server.URL)
+			})
+			_, err = s3v2Client.ListBuckets(context.Background(), &s3v2.ListBucketsInput{})
+			require.NoError(t, err)
+			assert.Equal(t, testCase.wantOrder, recorder.order)
+		})
+	}
+}
+
 func TestConfigureSDKv1(t *testing.T) {
 	middleware, recorder, server := setup(t)
+	defer server.Close()
 	client := awstesting.NewClient(&awsv1.Config{
 		Region:     awsv1.String("mock-region"),
 		DisableSSL: awsv1.Bool(true),
@@ -131,9 +213,10 @@ func TestConfigureSDKv1(t *testing.T) {
 }
 
 func TestConfigureSDKv2(t *testing.T) {
-	mw, recorder, server := setup(t)
+	middleware, recorder, server := setup(t)
+	defer server.Close()
 	cfg := awsv2.Config{Region: "us-east-1"}
-	assert.NoError(t, ConfigureSDKv2(mw, &cfg))
+	assert.NoError(t, ConfigureSDKv2(middleware, &cfg))
 	s3Client := s3v2.NewFromConfig(cfg, func(options *s3v2.Options) {
 		options.BaseEndpoint = awsv2.String(server.URL)
 	})

extension/awsmiddleware/wrapper.go

@@ -25,7 +25,6 @@ func namedResponseHandler(handler ResponseHandler) request.NamedHandler {
 
 type requestMiddleware struct {
 	RequestHandler
-	position middleware.RelativePosition
 }
 
 var _ middleware.BuildMiddleware = (*requestMiddleware)(nil)
@@ -38,9 +37,14 @@ func (r requestMiddleware) HandleBuild(ctx context.Context, in middleware.BuildI
 	return next.HandleBuild(ctx, in)
 }
 
+func withBuildOption(rmw *requestMiddleware, position middleware.RelativePosition) func(stack *middleware.Stack) error {
+	return func(stack *middleware.Stack) error {
+		return stack.Build.Add(rmw, position)
+	}
+}
+
 type responseMiddleware struct {
 	ResponseHandler
-	position middleware.RelativePosition
 }
 
 var _ middleware.DeserializeMiddleware = (*responseMiddleware)(nil)
@@ -53,3 +57,9 @@ func (r responseMiddleware) HandleDeserialize(ctx context.Context, in middleware
 	}
 	return
 }
+
+func withDeserializeOption(rmw *responseMiddleware, position middleware.RelativePosition) func(stack *middleware.Stack) error {
+	return func(stack *middleware.Stack) error {
+		return stack.Deserialize.Add(rmw, position)
+	}
+}