feat: adds Location in CompleteMultipartUpload response

Closes #1714

There is a `Location` field in the `CompleteMultipartUpload` result that represents the newly created object URL. This PR adds this property to the `CompleteMultipartUpload` response, generating it dynamically in either host-style or path-style format, depending on the gateway configuration.

s3api/controllers/base.go

@@ -31,12 +31,13 @@ import (
 )
 
 type S3ApiController struct {
-	be       backend.Backend
-	iam      auth.IAMService
-	logger   s3log.AuditLogger
-	evSender s3event.S3EventSender
-	mm       metrics.Manager
-	readonly bool
+	be            backend.Backend
+	iam           auth.IAMService
+	logger        s3log.AuditLogger
+	evSender      s3event.S3EventSender
+	mm            metrics.Manager
+	readonly      bool
+	virtualDomain string
 }
 
 const (
@@ -56,14 +57,15 @@ var (
 	xmlhdr = []byte(`<?xml version="1.0" encoding="UTF-8"?>` + "\n")
 )
 
-func New(be backend.Backend, iam auth.IAMService, logger s3log.AuditLogger, evs s3event.S3EventSender, mm metrics.Manager, readonly bool) S3ApiController {
+func New(be backend.Backend, iam auth.IAMService, logger s3log.AuditLogger, evs s3event.S3EventSender, mm metrics.Manager, readonly bool, virtualDomain string) S3ApiController {
 	return S3ApiController{
-		be:       be,
-		iam:      iam,
-		logger:   logger,
-		evSender: evs,
-		readonly: readonly,
-		mm:       mm,
+		be:            be,
+		iam:           iam,
+		logger:        logger,
+		evSender:      evs,
+		readonly:      readonly,
+		mm:            mm,
+		virtualDomain: virtualDomain,
 	}
 }
 

s3api/controllers/object-post.go

@@ -352,6 +352,10 @@ func (c S3ApiController) CompleteMultipartUpload(ctx *fiber.Ctx) (*Response, err
 			IfMatch:           ifMatch,
 			IfNoneMatch:       ifNoneMatch,
 		})
+	if err == nil {
+		objUrl := utils.GenerateObjectLocation(ctx, c.virtualDomain, bucket, key)
+		res.Location = &objUrl
+	}
 	return &Response{
 		Data: res,
 		Headers: map[string]*string{

s3api/controllers/object-post_test.go

@@ -536,7 +536,8 @@ func TestS3ApiController_CompleteMultipartUpload(t *testing.T) {
 			output: testOutput{
 				response: &Response{
 					Data: s3response.CompleteMultipartUploadResult{
-						ETag: &ETag,
+						ETag:     &ETag,
+						Location: utils.GetStringPtr("http://example.com/bucket/object"),
 					},
 					Headers: map[string]*string{
 						"x-amz-version-id": &versionId,

s3api/router.go

@@ -30,8 +30,8 @@ type S3ApiRouter struct {
 	WithAdmSrv bool
 }
 
-func (sa *S3ApiRouter) Init(app *fiber.App, be backend.Backend, iam auth.IAMService, logger s3log.AuditLogger, aLogger s3log.AuditLogger, evs s3event.S3EventSender, mm metrics.Manager, readonly bool, region string, root middlewares.RootUserConfig) {
-	ctrl := controllers.New(be, iam, logger, evs, mm, readonly)
+func (sa *S3ApiRouter) Init(app *fiber.App, be backend.Backend, iam auth.IAMService, logger s3log.AuditLogger, aLogger s3log.AuditLogger, evs s3event.S3EventSender, mm metrics.Manager, readonly bool, region, virtualDomain string, root middlewares.RootUserConfig) {
+	ctrl := controllers.New(be, iam, logger, evs, mm, readonly, virtualDomain)
 	adminServices := &controllers.Services{
 		Logger: aLogger,
 	}

s3api/router_test.go

@@ -46,7 +46,7 @@ func TestS3ApiRouter_Init(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			tt.sa.Init(tt.args.app, tt.args.be, tt.args.iam, nil, nil, nil, nil, false, "us-east-1", middlewares.RootUserConfig{})
+			tt.sa.Init(tt.args.app, tt.args.be, tt.args.iam, nil, nil, nil, nil, false, "us-east-1", "", middlewares.RootUserConfig{})
 		})
 	}
 }

s3api/server.go

@@ -123,7 +123,7 @@ func New(
 		app.Use(middlewares.DebugLogger())
 	}
 
-	server.router.Init(app, be, iam, l, adminLogger, evs, mm, server.readonly, region, root)
+	server.router.Init(app, be, iam, l, adminLogger, evs, mm, server.readonly, region, server.virtualDomain, root)
 
 	return server, nil
 }

s3api/utils/utils.go

@@ -887,3 +887,26 @@ func ValidateVersionId(versionId string) error {
 
 	return nil
 }
+
+// GenerateObjectLocation generates the object location path-styled or host-styled
+// depending on the gateway configuration
+func GenerateObjectLocation(ctx *fiber.Ctx, virtualDomain, bucket, object string) string {
+	scheme := ctx.Protocol()
+	host := ctx.Hostname()
+
+	// escape the object name
+	obj := url.PathEscape(object)
+
+	if virtualDomain != "" && strings.Contains(host, virtualDomain) {
+		// the host already contains the bucket name
+		return fmt.Sprintf("%s://%s/%s", scheme, host, obj)
+	}
+
+	return fmt.Sprintf(
+		"%s://%s/%s/%s",
+		scheme,
+		host,
+		bucket,
+		obj,
+	)
+}

tests/integration/CompleteMultipartUpload.go

@@ -1631,6 +1631,13 @@ func CompleteMultipartUpload_success(s *S3Conf) error {
 		if getString(res.Key) != obj {
 			return fmt.Errorf("expected object key to be %v, instead got %v", obj, *res.Key)
 		}
+		location := constructObjectLocation(s.endpoint, bucket, obj, s.hostStyle)
+		if res.Location == nil {
+			return fmt.Errorf("expected non nil Location")
+		}
+		if *res.Location != location {
+			return fmt.Errorf("expected Location to be %s, instead got %s", location, *res.Location)
+		}
 
 		ctx, cancel = context.WithTimeout(context.Background(), shortTimeout)
 		resp, err := s3client.HeadObject(ctx, &s3.HeadObjectInput{

tests/integration/utils.go

@@ -480,6 +480,28 @@ func listObjects(client *s3.Client, bucket, prefix, delimiter string, maxKeys in
 	return contents, commonPrefixes, nil
 }
 
+func constructObjectLocation(endpoint, bucket, object string, hostStyle bool) string {
+	// Normalize endpoint (no trailing slash)
+	endpoint = strings.TrimRight(endpoint, "/")
+
+	if !hostStyle {
+		// Path-style: http://endpoint/bucket/object
+		return fmt.Sprintf("%s/%s/%s", endpoint, bucket, object)
+	}
+
+	// Host-style: http://bucket.endpoint/object
+	u, err := url.Parse(endpoint)
+	if err != nil || u.Host == "" {
+		// Fallback for raw host:port endpoints (e.g. "127.0.0.1:7070")
+		return fmt.Sprintf("http://%s.%s/%s", bucket, endpoint, object)
+	}
+
+	host := u.Host
+	u.Host = fmt.Sprintf("%s.%s", bucket, host)
+
+	return fmt.Sprintf("%s/%s", u.String(), object)
+}
+
 func hasObjNames(objs []types.Object, names []string) bool {
 	if len(objs) != len(names) {
 		return false