local snapshot save always has .zip extension

Author: anisaoshafi

internal/snapshot/destination.go

@@ -10,15 +10,16 @@ import (
 
 // ParseDestination resolves the user-supplied path to an absolute local path,
 // or returns an error for cloud/bare names. When dest is empty, a default name
-// based on now (UTC) is used, e.g. "snapshot-2026-05-11T21-04-32".
+// based on now (UTC) is used, e.g. "snapshot-2026-05-11T21-04-32.zip".
+// The returned path always has a .zip extension.
 func ParseDestination(dest string, now time.Time) (string, error) {
 	if dest == "" {
 		dest = "./" + now.UTC().Format("snapshot-2006-01-02T15-04-05")
 	} else if strings.Contains(dest, "://") {
-		return "", fmt.Errorf("cloud destinations are not yet supported — use a file path like ./my-snapshot")
+		return "", fmt.Errorf("cloud destinations are not yet supported — use a file path like ./my-snapshot.zip")
 	} else if !strings.HasPrefix(dest, ".") && !strings.HasPrefix(dest, "~") && !filepath.IsAbs(dest) && filepath.Base(dest) == dest {
 		// bare name with no path separators: reserved for future cloud pod names
-		return "", fmt.Errorf("cloud destinations are not yet supported — use a file path like ./my-snapshot")
+		return "", fmt.Errorf("cloud destinations are not yet supported — use a file path like ./my-snapshot.zip")
 	}
 	if dest == "~" || strings.HasPrefix(dest, "~/") || strings.HasPrefix(dest, `~\`) {
 		home, err := os.UserHomeDir()
@@ -31,5 +32,11 @@ func ParseDestination(dest string, now time.Time) (string, error) {
 	if err != nil {
 		return "", fmt.Errorf("resolve path: %w", err)
 	}
+	if info, err := os.Stat(abs); err == nil && info.IsDir() {
+		return "", fmt.Errorf("%q is a directory — specify a file path like ./my-snapshot.zip", abs)
+	}
+	if !strings.EqualFold(filepath.Ext(abs), ".zip") {
+		abs += ".zip"
+	}
 	return abs, nil
 }

internal/snapshot/destination_test.go

@@ -12,6 +12,15 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestParseDestinationRejectsDirectory(t *testing.T) {
+	t.Parallel()
+	dir := t.TempDir()
+	now := time.Date(2026, 5, 11, 21, 4, 32, 0, time.UTC)
+	_, err := snapshot.ParseDestination(dir, now)
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "is a directory")
+}
+
 func TestParseDestinationDefault(t *testing.T) {
 	t.Parallel()
 	wd, err := os.Getwd()
@@ -20,7 +29,7 @@ func TestParseDestinationDefault(t *testing.T) {
 	now := time.Date(2026, 5, 11, 21, 4, 32, 0, time.UTC)
 	got, err := snapshot.ParseDestination("", now)
 	require.NoError(t, err)
-	assert.Equal(t, filepath.Join(wd, "snapshot-2026-05-11T21-04-32"), got)
+	assert.Equal(t, filepath.Join(wd, "snapshot-2026-05-11T21-04-32.zip"), got)
 }
 
 func TestParseDestination(t *testing.T) {
@@ -33,51 +42,63 @@ func TestParseDestination(t *testing.T) {
 	now := time.Date(2026, 5, 11, 21, 4, 32, 0, time.UTC)
 
 	type testCase struct {
-		input    string
-		wantPath string
-		wantErr  string
+		input        string
+		wantPath     string
+		wantErr      string
+		wantCloudErr bool
 	}
 
 	tests := []testCase{
 		{
 			input:    "./my-state",
-			wantPath: filepath.Join(wd, "my-state"),
+			wantPath: filepath.Join(wd, "my-state.zip"),
 		},
 		{
 			input:    filepath.Join(os.TempDir(), "state"),
-			wantPath: filepath.Join(os.TempDir(), "state"),
+			wantPath: filepath.Join(os.TempDir(), "state.zip"),
 		},
 		{
 			input:    "~",
-			wantPath: home,
+			wantErr:  "is a directory",
 		},
 		{
 			input:    "~/snapshots/s",
-			wantPath: filepath.Join(home, "snapshots", "s"),
+			wantPath: filepath.Join(home, "snapshots", "s.zip"),
 		},
 		{
 			input:    "subdir/state",
-			wantPath: filepath.Join(wd, "subdir", "state"),
+			wantPath: filepath.Join(wd, "subdir", "state.zip"),
+		},
+		{
+			input:    "./checkpoint.zip",
+			wantPath: filepath.Join(wd, "checkpoint.zip"),
+		},
+		{
+			input:    "./already.ZIP",
+			wantPath: filepath.Join(wd, "already.ZIP"),
 		},
 		{
-			input:   "my-pod",
-			wantErr: "cloud destinations are not yet supported",
+			input:        "my-pod",
+			wantErr:      "cloud destinations are not yet supported",
+			wantCloudErr: true,
 		},
 		{
-			input:   "cloud://my-pod",
-			wantErr: "cloud destinations are not yet supported",
+			input:        "cloud://my-pod",
+			wantErr:      "cloud destinations are not yet supported",
+			wantCloudErr: true,
 		},
 		{
-			input:   "s3://bucket/key",
-			wantErr: "cloud destinations are not yet supported",
+			input:        "s3://bucket/key",
+			wantErr:      "cloud destinations are not yet supported",
+			wantCloudErr: true,
 		},
 	}
 
 	if runtime.GOOS == "windows" {
 		tests = append(tests,
-			testCase{input: `~\snapshots\s`, wantPath: filepath.Join(home, "snapshots", "s")},
-			testCase{input: `C:\Users\user\snap`, wantPath: `C:\Users\user\snap`},
-			testCase{input: `C:/Users/user/snap`, wantPath: `C:\Users\user\snap`},
+			testCase{input: `~\snapshots\s`, wantPath: filepath.Join(home, "snapshots", "s.zip")},
+			testCase{input: `C:\Users\user\snap`, wantPath: `C:\Users\user\snap.zip`},
+			testCase{input: `C:/Users/user/snap`, wantPath: `C:\Users\user\snap.zip`},
 		)
 	}
 
@@ -88,7 +109,9 @@ func TestParseDestination(t *testing.T) {
 			if tc.wantErr != "" {
 				require.Error(t, err)
 				assert.Contains(t, err.Error(), tc.wantErr)
-				assert.Contains(t, err.Error(), "./my-snapshot")
+				if tc.wantCloudErr {
+					assert.Contains(t, err.Error(), "./my-snapshot.zip")
+				}
 				return
 			}
 			require.NoError(t, err)

test/integration/snapshot_save_test.go

@@ -82,7 +82,7 @@ func TestSnapshotSaveCustomPath(t *testing.T) {
 	startTestContainer(t, ctx)
 	srv := mockStateServer(t)
 	dir := t.TempDir()
-	outPath := filepath.Join(dir, "my-snap")
+	outPath := filepath.Join(dir, "my-snap.zip")
 
 	stdout, stderr, err := runLstk(t, ctx, dir,
 		env.With(env.LocalStackHost, lsHost(srv)),
@@ -118,7 +118,7 @@ func TestSnapshotSaveRelativePath(t *testing.T) {
 	require.NoError(t, err, "lstk snapshot save failed: %s", stderr)
 	assert.Contains(t, stdout, "Snapshot saved")
 
-	_, statErr := os.Stat(filepath.Join(dir, "my-state"))
+	_, statErr := os.Stat(filepath.Join(dir, "my-state.zip"))
 	assert.NoError(t, statErr, "relative output file should exist")
 }
 
@@ -131,7 +131,7 @@ func TestSnapshotSaveOverwritesExistingFile(t *testing.T) {
 	startTestContainer(t, ctx)
 	srv := mockStateServer(t)
 	dir := t.TempDir()
-	outPath := filepath.Join(dir, "snap")
+	outPath := filepath.Join(dir, "snap.zip")
 	require.NoError(t, os.WriteFile(outPath, []byte("OLD"), 0600))
 
 	_, stderr, err := runLstk(t, ctx, dir,