client: make ImageSaveResult an interface

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

client/image_save.go

@@ -2,9 +2,14 @@ package client
 
 import (
 	"context"
+	"io"
 	"net/url"
 )
 
+type ImageSaveResult interface {
+	io.ReadCloser
+}
+
 // ImageSave retrieves one or more images from the docker host as an
 // [ImageSaveResult].
 //
@@ -15,7 +20,7 @@ func (cli *Client) ImageSave(ctx context.Context, imageIDs []string, saveOpts ..
 	var opts imageSaveOpts
 	for _, opt := range saveOpts {
 		if err := opt.Apply(&opts); err != nil {
-			return ImageSaveResult{}, err
+			return nil, err
 		}
 	}
 
@@ -25,18 +30,44 @@ func (cli *Client) ImageSave(ctx context.Context, imageIDs []string, saveOpts ..
 
 	if len(opts.apiOptions.Platforms) > 0 {
 		if err := cli.requiresVersion(ctx, "1.48", "platform"); err != nil {
-			return ImageSaveResult{}, err
+			return nil, err
 		}
 		p, err := encodePlatforms(opts.apiOptions.Platforms...)
 		if err != nil {
-			return ImageSaveResult{}, err
+			return nil, err
 		}
 		query["platform"] = p
 	}
 
 	resp, err := cli.get(ctx, "/images/get", query, nil)
 	if err != nil {
-		return ImageSaveResult{}, err
+		return nil, err
 	}
-	return newImageSaveResult(resp.Body), nil
+	return &imageSaveResult{
+		body: resp.Body,
+	}, nil
+}
+
+type imageSaveResult struct {
+	// body must be closed to avoid a resource leak
+	body io.ReadCloser
+}
+
+var (
+	_ io.ReadCloser   = (*imageSaveResult)(nil)
+	_ ImageSaveResult = (*imageSaveResult)(nil)
+)
+
+func (r *imageSaveResult) Read(p []byte) (int, error) {
+	if r == nil || r.body == nil {
+		return 0, io.EOF
+	}
+	return r.body.Read(p)
+}
+
+func (r *imageSaveResult) Close() error {
+	if r == nil || r.body == nil {
+		return nil
+	}
+	return r.body.Close()
 }

client/image_save_opts.go

@@ -2,8 +2,6 @@ package client
 
 import (
 	"fmt"
-	"io"
-	"sync"
 
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
@@ -38,34 +36,3 @@ type imageSaveOptions struct {
 	// multi-platform image and has multiple variants.
 	Platforms []ocispec.Platform
 }
-
-func newImageSaveResult(rc io.ReadCloser) ImageSaveResult {
-	if rc == nil {
-		panic("nil io.ReadCloser")
-	}
-	return ImageSaveResult{
-		rc:    rc,
-		close: sync.OnceValue(rc.Close),
-	}
-}
-
-type ImageSaveResult struct {
-	rc    io.ReadCloser
-	close func() error
-}
-
-// Read implements io.ReadCloser
-func (r ImageSaveResult) Read(p []byte) (n int, err error) {
-	if r.rc == nil {
-		return 0, io.EOF
-	}
-	return r.rc.Read(p)
-}
-
-// Close implements io.ReadCloser
-func (r ImageSaveResult) Close() error {
-	if r.close == nil {
-		return nil
-	}
-	return r.close()
-}