Update

vendor/github.com/aws/smithy-go/middleware/step_build.go

@@ -1,7 +1,9 @@
+// Code generated by smithy-go/middleware/generate.go DO NOT EDIT.
 package middleware
 
 import (
 	"context"
+	"fmt"
 )
 
 // BuildInput provides the input parameters for the BuildMiddleware to consume.
@@ -25,14 +27,14 @@ type BuildHandler interface {
 }
 
 // BuildMiddleware provides the interface for middleware specific to the
-// serialize step. Delegates to the next BuildHandler for further
+// build step. Delegates to the next BuildHandler for further
 // processing.
 type BuildMiddleware interface {
-	// Unique ID for the middleware in theBuildStep. The step does not allow
-	// duplicate IDs.
+	// ID returns a unique ID for the middleware in the BuildStep. The step does not
+	// allow duplicate IDs.
 	ID() string
 
-	// Invokes the middleware behavior which must delegate to the next handler
+	// HandleBuild invokes the middleware behavior which must delegate to the next handler
 	// for the middleware chain to continue. The method must return a result or
 	// error to its caller.
 	HandleBuild(ctx context.Context, in BuildInput, next BuildHandler) (
@@ -54,7 +56,9 @@ type buildMiddlewareFunc struct {
 	id string
 
 	// Middleware function to be called.
-	fn func(context.Context, BuildInput, BuildHandler) (BuildOutput, Metadata, error)
+	fn func(context.Context, BuildInput, BuildHandler) (
+		BuildOutput, Metadata, error,
+	)
 }
 
 // ID returns the unique ID for the middleware.
@@ -69,23 +73,22 @@ func (s buildMiddlewareFunc) HandleBuild(ctx context.Context, in BuildInput, nex
 
 var _ BuildMiddleware = (buildMiddlewareFunc{})
 
-// BuildStep provides the ordered grouping of BuildMiddleware to be invoked on
-// a handler.
+// BuildStep provides the ordered grouping of BuildMiddleware to be
+// invoked on a handler.
 type BuildStep struct {
-	ids *orderedIDs
+	head *decoratedBuildHandler
+	tail *decoratedBuildHandler
 }
 
-// NewBuildStep returns a BuildStep ready to have middleware for
-// initialization added to it.
+// NewBuildStep returns an BuildStep ready to have middleware for
+// build added to it.
 func NewBuildStep() *BuildStep {
-	return &BuildStep{
-		ids: newOrderedIDs(),
-	}
+	return &BuildStep{}
 }
 
 var _ Middleware = (*BuildStep)(nil)
 
-// ID returns the unique name of the step as a middleware.
+// ID returns the unique ID of the step as a middleware.
 func (s *BuildStep) ID() string {
 	return "Build stack step"
 }
@@ -97,77 +100,161 @@ func (s *BuildStep) ID() string {
 func (s *BuildStep) HandleMiddleware(ctx context.Context, in interface{}, next Handler) (
 	out interface{}, metadata Metadata, err error,
 ) {
-	order := s.ids.GetOrder()
-
-	var h BuildHandler = buildWrapHandler{Next: next}
-	for i := len(order) - 1; i >= 0; i-- {
-		h = decoratedBuildHandler{
-			Next: h,
-			With: order[i].(BuildMiddleware),
-		}
-	}
-
 	sIn := BuildInput{
 		Request: in,
 	}
 
-	res, metadata, err := h.HandleBuild(ctx, sIn)
+	wh := &buildWrapHandler{next}
+	if s.head == nil {
+		res, metadata, err := wh.HandleBuild(ctx, sIn)
+		return res.Result, metadata, err
+	}
+
+	s.tail.Next = wh
+	res, metadata, err := s.head.HandleBuild(ctx, sIn)
 	return res.Result, metadata, err
 }
 
 // Get retrieves the middleware identified by id. If the middleware is not present, returns false.
 func (s *BuildStep) Get(id string) (BuildMiddleware, bool) {
-	get, ok := s.ids.Get(id)
-	if !ok {
+	found, _ := s.get(id)
+	if found == nil {
 		return nil, false
 	}
-	return get.(BuildMiddleware), ok
+
+	return found.With, true
 }
 
 // Add injects the middleware to the relative position of the middleware group.
-// Returns an error if the middleware already exists.
+//
+// Add never returns an error. It used to for duplicate phases but this
+// behavior has since been removed as part of a performance optimization. The
+// return value from Add can be ignored.
 func (s *BuildStep) Add(m BuildMiddleware, pos RelativePosition) error {
-	return s.ids.Add(m, pos)
+	if s.head == nil {
+		s.head = &decoratedBuildHandler{nil, m}
+		s.tail = s.head
+		return nil
+	}
+
+	if pos == Before {
+		s.head = &decoratedBuildHandler{s.head, m}
+	} else {
+		tail := &decoratedBuildHandler{nil, m}
+		s.tail.Next = tail
+		s.tail = tail
+	}
+
+	return nil
 }
 
-// Insert injects the middleware relative to an existing middleware id.
-// Returns an error if the original middleware does not exist, or the middleware
+// Insert injects the middleware relative to an existing middleware ID.
+// Returns error if the original middleware does not exist, or the middleware
 // being added already exists.
 func (s *BuildStep) Insert(m BuildMiddleware, relativeTo string, pos RelativePosition) error {
-	return s.ids.Insert(m, relativeTo, pos)
+	found, prev := s.get(relativeTo)
+	if found == nil {
+		return fmt.Errorf("not found: %s", m.ID())
+	}
+
+	if pos == Before {
+		if prev == nil { // at the front
+			s.head = &decoratedBuildHandler{s.head, m}
+		} else { // somewhere in the middle
+			prev.Next = &decoratedBuildHandler{found, m}
+		}
+	} else {
+		if found.Next == nil { // at the end
+			tail := &decoratedBuildHandler{nil, m}
+			s.tail.Next = tail
+			s.tail = tail
+		} else { // somewhere in the middle
+			found.Next = &decoratedBuildHandler{found.Next, m}
+		}
+	}
+
+	return nil
 }
 
 // Swap removes the middleware by id, replacing it with the new middleware.
-// Returns the middleware removed, or an error if the middleware to be removed
+// Returns the middleware removed, or error if the middleware to be removed
 // doesn't exist.
 func (s *BuildStep) Swap(id string, m BuildMiddleware) (BuildMiddleware, error) {
-	removed, err := s.ids.Swap(id, m)
-	if err != nil {
-		return nil, err
+	found, _ := s.get(id)
+	if found == nil {
+		return nil, fmt.Errorf("not found: %s", m.ID())
 	}
 
-	return removed.(BuildMiddleware), nil
+	swapped := found.With
+	found.With = m
+	return swapped, nil
 }
 
 // Remove removes the middleware by id. Returns error if the middleware
 // doesn't exist.
 func (s *BuildStep) Remove(id string) (BuildMiddleware, error) {
-	removed, err := s.ids.Remove(id)
-	if err != nil {
-		return nil, err
+	found, prev := s.get(id)
+	if found == nil {
+		return nil, fmt.Errorf("not found: %s", id)
 	}
 
-	return removed.(BuildMiddleware), nil
+	if s.head == s.tail { // it's the only one
+		s.head = nil
+		s.tail = nil
+	} else if found == s.head { // at the front
+		s.head = s.head.Next.(*decoratedBuildHandler)
+	} else if found == s.tail { // at the end
+		prev.Next = nil
+		s.tail = prev
+	} else {
+		prev.Next = found.Next // somewhere in the middle
+	}
+
+	return found.With, nil
 }
 
 // List returns a list of the middleware in the step.
 func (s *BuildStep) List() []string {
-	return s.ids.List()
+	var ids []string
+	for h := s.head; h != nil; {
+		ids = append(ids, h.With.ID())
+		if h.Next == nil {
+			break
+		}
+
+		// once executed, tail.Next of the list will be set to an
+		// *buildWrapHandler, make sure to check for that
+		if hnext, ok := h.Next.(*decoratedBuildHandler); ok {
+			h = hnext
+		} else {
+			break
+		}
+	}
+	return ids
 }
 
 // Clear removes all middleware in the step.
 func (s *BuildStep) Clear() {
-	s.ids.Clear()
+	s.head = nil
+	s.tail = nil
+}
+
+func (s *BuildStep) get(id string) (found, prev *decoratedBuildHandler) {
+	for h := s.head; h != nil; {
+		if h.With.ID() == id {
+			found = h
+			return
+		}
+		prev = h
+		if h.Next == nil {
+			return
+		}
+
+		// once executed, tail.Next of the list will be set to an
+		// *buildWrapHandler
+		h, _ = h.Next.(*decoratedBuildHandler)
+	}
+	return
 }
 
 type buildWrapHandler struct {
@@ -176,7 +263,7 @@ type buildWrapHandler struct {
 
 var _ BuildHandler = (*buildWrapHandler)(nil)
 
-// Implements BuildHandler, converts types and delegates to underlying
+// HandleBuild implements BuildHandler, converts types and delegates to underlying
 // generic handler.
 func (w buildWrapHandler) HandleBuild(ctx context.Context, in BuildInput) (
 	out BuildOutput, metadata Metadata, err error,
@@ -200,12 +287,12 @@ func (h decoratedBuildHandler) HandleBuild(ctx context.Context, in BuildInput) (
 	return h.With.HandleBuild(ctx, in, h.Next)
 }
 
-// BuildHandlerFunc provides a wrapper around a function to be used as a build middleware handler.
+// BuildHandlerFunc provides a wrapper around a function to be used as buildMiddleware.
 type BuildHandlerFunc func(context.Context, BuildInput) (BuildOutput, Metadata, error)
 
-// HandleBuild invokes the wrapped function with the provided arguments.
-func (b BuildHandlerFunc) HandleBuild(ctx context.Context, in BuildInput) (BuildOutput, Metadata, error) {
-	return b(ctx, in)
+// HandleBuild calls the wrapped function with the provided arguments.
+func (f BuildHandlerFunc) HandleBuild(ctx context.Context, in BuildInput) (BuildOutput, Metadata, error) {
+	return f(ctx, in)
 }
 
 var _ BuildHandler = BuildHandlerFunc(nil)