Fix docker cp success message to report actual content size instead of tar stream size

cli/command/container/client_test.go

@@ -36,6 +36,7 @@ type fakeClient struct {
 	infoFunc                func() (client.SystemInfoResult, error)
 	containerStatPathFunc   func(containerID, path string) (client.ContainerStatPathResult, error)
 	containerCopyFromFunc   func(containerID, srcPath string) (client.CopyFromContainerResult, error)
+	containerCopyToFunc     func(containerID string, options client.CopyToContainerOptions) (client.CopyToContainerResult, error)
 	logFunc                 func(string, client.ContainerLogsOptions) (client.ContainerLogsResult, error)
 	waitFunc                func(string) client.ContainerWaitResult
 	containerListFunc       func(client.ContainerListOptions) (client.ContainerListResult, error)
@@ -128,6 +129,13 @@ func (f *fakeClient) CopyFromContainer(_ context.Context, containerID string, op
 	return client.CopyFromContainerResult{}, nil
 }
 
+func (f *fakeClient) CopyToContainer(_ context.Context, containerID string, options client.CopyToContainerOptions) (client.CopyToContainerResult, error) {
+	if f.containerCopyToFunc != nil {
+		return f.containerCopyToFunc(containerID, options)
+	}
+	return client.CopyToContainerResult{}, nil
+}
+
 func (f *fakeClient) ContainerLogs(_ context.Context, containerID string, options client.ContainerLogsOptions) (client.ContainerLogsResult, error) {
 	if f.logFunc != nil {
 		return f.logFunc(containerID, options)

cli/command/container/cp.go

@@ -168,6 +168,34 @@ func progressHumanSize(n int64) string {
 	return units.HumanSizeWithPrecision(float64(n), 3)
 }
 
+// localContentSize returns the total size of regular file content at path.
+// For a regular file it returns the file size. For a directory it walks
+// the tree and sums sizes of all regular files.
+func localContentSize(path string) (int64, error) {
+	fi, err := os.Lstat(path)
+	if err != nil {
+		return -1, err
+	}
+	if !fi.IsDir() {
+		return fi.Size(), nil
+	}
+	var total int64
+	err = filepath.WalkDir(path, func(_ string, d os.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.Type().IsRegular() {
+			info, err := d.Info()
+			if err != nil {
+				return err
+			}
+			total += info.Size()
+		}
+		return nil
+	})
+	return total, err
+}
+
 func runCopy(ctx context.Context, dockerCli command.Cli, opts copyOptions) error {
 	srcContainer, srcPath := splitCpArg(opts.source)
 	destContainer, destPath := splitCpArg(opts.destination)
@@ -295,7 +323,11 @@ func copyFromContainer(ctx context.Context, dockerCLI command.Cli, copyConfig cp
 	cancel()
 	<-done
 	restore()
-	_, _ = fmt.Fprintln(dockerCLI.Err(), "Successfully copied", progressHumanSize(copiedSize), "to", dstPath)
+	reportedSize := copiedSize
+	if !cpRes.Stat.Mode.IsDir() {
+		reportedSize = cpRes.Stat.Size
+	}
+	_, _ = fmt.Fprintln(dockerCLI.Err(), "Successfully copied", progressHumanSize(reportedSize), "to", dstPath)
 
 	return res
 }
@@ -354,6 +386,8 @@ func copyToContainer(ctx context.Context, dockerCLI command.Cli, copyConfig cpCo
 		content         io.ReadCloser
 		resolvedDstPath string
 		copiedSize      int64
+		contentSize     int64
+		sizeErr         error
 	)
 
 	if srcPath == "-" {
@@ -369,6 +403,8 @@ func copyToContainer(ctx context.Context, dockerCLI command.Cli, copyConfig cpCo
 			return err
 		}
 
+		contentSize, sizeErr = localContentSize(srcInfo.Path)
+
 		srcArchive, err := archive.TarResource(srcInfo)
 		if err != nil {
 			return err
@@ -421,7 +457,11 @@ func copyToContainer(ctx context.Context, dockerCLI command.Cli, copyConfig cpCo
 	cancel()
 	<-done
 	restore()
-	_, _ = fmt.Fprintln(dockerCLI.Err(), "Successfully copied", progressHumanSize(copiedSize), "to", copyConfig.container+":"+dstInfo.Path)
+	reportedSize := copiedSize
+	if sizeErr == nil {
+		reportedSize = contentSize
+	}
+	_, _ = fmt.Fprintln(dockerCLI.Err(), "Successfully copied", progressHumanSize(reportedSize), "to", copyConfig.container+":"+dstInfo.Path)
 
 	return err
 }

cli/command/container/cp_test.go

@@ -11,6 +11,7 @@ import (
 	"github.com/docker/cli/internal/test"
 	"github.com/moby/go-archive"
 	"github.com/moby/go-archive/compression"
+	"github.com/moby/moby/api/types/container"
 	"github.com/moby/moby/client"
 	"gotest.tools/v3/assert"
 	is "gotest.tools/v3/assert/cmp"
@@ -211,3 +212,86 @@ func TestRunCopyFromContainerToFilesystemIrregularDestination(t *testing.T) {
 	expected := `"/dev/random" must be a directory or a regular file`
 	assert.ErrorContains(t, err, expected)
 }
+
+func TestCopyFromContainerReportsFileSize(t *testing.T) {
+	// The file content is "hello" (5 bytes), but the TAR archive wrapping
+	// it is much larger due to headers and padding. The success message
+	// should report the actual file size (5B), not the TAR stream size.
+	srcDir := fs.NewDir(t, "cp-test-from",
+		fs.WithFile("file1", "hello"))
+
+	destDir := fs.NewDir(t, "cp-test-from-dest")
+
+	const fileSize int64 = 5
+	fakeCli := test.NewFakeCli(&fakeClient{
+		containerCopyFromFunc: func(ctr, srcPath string) (client.CopyFromContainerResult, error) {
+			readCloser, err := archive.Tar(srcDir.Path(), compression.None)
+			return client.CopyFromContainerResult{
+				Content: readCloser,
+				Stat: container.PathStat{
+					Name: "file1",
+					Size: fileSize,
+				},
+			}, err
+		},
+	})
+	err := runCopy(context.TODO(), fakeCli, copyOptions{
+		source:      "container:/file1",
+		destination: destDir.Path(),
+	})
+	assert.NilError(t, err)
+	assert.Check(t, is.Contains(fakeCli.ErrBuffer().String(), "5B"))
+}
+
+func TestCopyToContainerReportsFileSize(t *testing.T) {
+	// Create a temp file with known content ("hello" = 5 bytes).
+	// The TAR archive sent to the container is larger, but the success
+	// message should report the actual content size.
+	srcFile := fs.NewFile(t, "cp-test-to", fs.WithContent("hello"))
+
+	fakeCli := test.NewFakeCli(&fakeClient{
+		containerStatPathFunc: func(containerID, path string) (client.ContainerStatPathResult, error) {
+			return client.ContainerStatPathResult{
+				Stat: container.PathStat{
+					Name: "tmp",
+					Mode: os.ModeDir | 0o755,
+				},
+			}, nil
+		},
+		containerCopyToFunc: func(containerID string, options client.CopyToContainerOptions) (client.CopyToContainerResult, error) {
+			_, _ = io.Copy(io.Discard, options.Content)
+			return client.CopyToContainerResult{}, nil
+		},
+	})
+	err := runCopy(context.TODO(), fakeCli, copyOptions{
+		source:      srcFile.Path(),
+		destination: "container:/tmp",
+	})
+	assert.NilError(t, err)
+	assert.Check(t, is.Contains(fakeCli.ErrBuffer().String(), "5B"))
+}
+
+func TestCopyToContainerReportsEmptyFileSize(t *testing.T) {
+	srcFile := fs.NewFile(t, "cp-test-empty", fs.WithContent(""))
+
+	fakeCli := test.NewFakeCli(&fakeClient{
+		containerStatPathFunc: func(containerID, path string) (client.ContainerStatPathResult, error) {
+			return client.ContainerStatPathResult{
+				Stat: container.PathStat{
+					Name: "tmp",
+					Mode: os.ModeDir | 0o755,
+				},
+			}, nil
+		},
+		containerCopyToFunc: func(containerID string, options client.CopyToContainerOptions) (client.CopyToContainerResult, error) {
+			_, _ = io.Copy(io.Discard, options.Content)
+			return client.CopyToContainerResult{}, nil
+		},
+	})
+	err := runCopy(context.TODO(), fakeCli, copyOptions{
+		source:      srcFile.Path(),
+		destination: "container:/tmp",
+	})
+	assert.NilError(t, err)
+	assert.Check(t, is.Contains(fakeCli.ErrBuffer().String(), "0B"))
+}