Print an empty unlocker or vault list as [] in JSON (closes #148)

`secret unlocker list --json` printed "unlockers": null for a vault with
no unlockers, and `secret vault list --json` printed "vaults": null when
vaults.d held no vaults. Both lists were nil slices, which encoding/json
writes as null. Each is now made as an empty slice before it is filled,
so an empty list prints as [].

vault.ListVaults therefore returns an empty slice instead of nil for an
empty vaults.d; its other callers only range over the result or check
its length.

Model: opus-5-5

internal/cli/unlockers.go

@@ -314,7 +314,8 @@ func (cli *Instance) UnlockersList(jsonOutput bool) error {
 		return err
 	}
 
-	var unlockers []UnlockerInfo
+	// Not nil, so that a vault with no unlockers prints [] in JSON, not null
+	unlockers := make([]UnlockerInfo, 0, len(unlockerMetadata))
 
 	for _, unlockerID := range slices.Sorted(maps.Keys(unlockerMetadata)) {
 		metadata := unlockerMetadata[unlockerID]

internal/cli/unlockers_list_test.go

@@ -1,13 +1,14 @@
 // Unlocker List Tests
 //
-// Tests for `secret unlocker list` behavior when an unlocker's metadata
-// cannot be read or used:
+// Tests for `secret unlocker list`:
 //
 //   - TestUnlockersListToleratesCorruptMetadata: one unlocker's corrupt
 //     metadata does not stop the others from being listed.
 //   - TestUnlockersListSkipsUnreadableMetadata: an unlocker whose metadata
 //     file cannot be checked for or read is left out, and the other is
 //     still listed.
+//   - TestUnlockersListEmptyJSON: a vault with no unlockers lists them as
+//     an empty JSON list.
 
 //nolint:testpackage // white-box test of unexported internals
 package cli
@@ -321,3 +322,36 @@ func TestUnlockersListSkipsUnreadableMetadata(t *testing.T) {
 		})
 	}
 }
+
+// TestUnlockersListEmptyJSON is a regression test for
+// https://git.eeqj.de/sneak/secret/issues/148: listing the unlockers of a
+// vault that has none, as after its last unlocker is removed, printed
+// "unlockers": null in JSON form instead of an empty list.
+func TestUnlockersListEmptyJSON(t *testing.T) {
+	t.Parallel()
+
+	fs := afero.NewMemMapFs()
+	vaultDir := filepath.Join(listTestStateDir, "vaults.d", listTestVaultName)
+
+	require.NoError(t, afero.WriteFile(
+		fs, filepath.Join(listTestStateDir, "currentvault"),
+		[]byte(listTestVaultName), listTestFilePerm,
+	))
+	require.NoError(t, fs.MkdirAll(
+		filepath.Join(vaultDir, listTestUnlockersDirName), listTestDirPerm,
+	))
+
+	var buf bytes.Buffer
+
+	cmd := &cobra.Command{}
+	cmd.SetOut(&buf)
+
+	instance := &Instance{fs: fs, stateDir: listTestStateDir, cmd: cmd}
+	require.NoError(t, instance.UnlockersList(true))
+
+	var decoded map[string]any
+
+	require.NoError(t, json.Unmarshal(buf.Bytes(), &decoded))
+	assert.Equal(t, []any{}, decoded["unlockers"],
+		"no unlockers must be printed as [], not %s", buf.String())
+}

internal/cli/vault_list_test.go

@@ -0,0 +1,42 @@
+package cli_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"path/filepath"
+	"testing"
+
+	"github.com/spf13/afero"
+	"github.com/spf13/cobra"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/secret/internal/cli"
+	"sneak.berlin/go/secret/internal/secret"
+)
+
+// TestVaultListEmptyJSON is a regression test for
+// https://git.eeqj.de/sneak/secret/issues/148: listing the vaults when
+// vaults.d holds none printed "vaults": null in JSON form instead of an
+// empty list.
+func TestVaultListEmptyJSON(t *testing.T) {
+	t.Parallel()
+
+	fs := afero.NewMemMapFs()
+	require.NoError(t, fs.MkdirAll(
+		filepath.Join(testStateDir, "vaults.d"), secret.DirPerms,
+	))
+
+	var buf bytes.Buffer
+
+	cmd := &cobra.Command{}
+	cmd.SetOut(&buf)
+
+	c := cli.NewCLIInstanceWithStateDir(fs, testStateDir)
+	require.NoError(t, c.ListVaults(cmd, true))
+
+	var decoded map[string]any
+
+	require.NoError(t, json.Unmarshal(buf.Bytes(), &decoded))
+	assert.Equal(t, []any{}, decoded["vaults"],
+		"no vaults must be printed as [], not %s", buf.String())
+}

internal/cli/version.go

@@ -64,7 +64,7 @@ func VersionCommands(cli *Instance) *cobra.Command {
 	promoteCmd := &cobra.Command{
 		Use:   "promote <secret-name> <version>",
 		Short: "Promote a specific version to current",
-		Long: "Updates the current symlink to point to the specified " +
+		Long: "Rewrites the secret's current file to name the specified " +
 			"version. The versions' own times are left unchanged; secret " +
 			"list then gives the time of the promote as the secret's last " +
 			"update.",
@@ -293,7 +293,7 @@ func (cli *Instance) PromoteVersion(
 			version, vault.ErrVersionNotFound, secretName)
 	}
 
-	// Update the current symlink using the proper function
+	// Rewrite the secret's current file to name the version
 	err = secret.SetCurrentVersion(cli.fs, secretDir, version)
 	if err != nil {
 		return fmt.Errorf("failed to update current version: %w", err)

internal/cli/version_test.go

@@ -6,6 +6,8 @@
 // - TestListVersionsNonExistentSecret: Tests error handling for missing secrets
 // - TestPromoteVersionCommand: Tests `secret version promote` command
 // - TestPromoteNonExistentVersion: Tests error handling for invalid promotion
+// - TestPromoteHelpSaysCurrentFileIsRewritten: Tests `secret version promote
+//   --help` text
 // - TestGetSecretWithVersion: Tests `secret get --version` flag functionality
 // - TestGetSecretWritesBinaryValue: Tests `secret get` output of binary values
 // - TestGetSecretReturnsWriteError: Tests `secret get` when stdout fails
@@ -270,6 +272,23 @@ func TestPromoteNonExistentVersion(t *testing.T) {
 	require.ErrorIs(t, err, vault.ErrVersionNotFound)
 }
 
+// TestPromoteHelpSaysCurrentFileIsRewritten is a regression test for
+// https://git.eeqj.de/sneak/secret/issues/153: `secret version promote
+// --help` said it updates a symlink, but promote rewrites the secret's
+// `current` file, which is a plain file.
+//
+//nolint:paralleltest // executes the CLI in-process and sets the environment
+func TestPromoteHelpSaysCurrentFileIsRewritten(t *testing.T) {
+	env := map[string]string{secret.EnvStateDir: t.TempDir()}
+
+	output, err := ExecuteCommandInProcess(
+		[]string{"version", "promote", "--help"}, "", env)
+	require.NoError(t, err)
+
+	assert.NotContains(t, output, "symlink")
+	assert.Contains(t, output, "current file")
+}
+
 func TestGetSecretWithVersion(t *testing.T) {
 	t.Parallel()
 

internal/vault/management.go

@@ -140,8 +140,9 @@ func ListVaults(fs afero.Fs, stateDir string) ([]string, error) {
 		return nil, fmt.Errorf("failed to read vaults directory: %w", err)
 	}
 
-	// Extract vault names
-	var vaults []string
+	// Extract vault names. Not nil, so that no vaults prints [] in JSON,
+	// not null.
+	vaults := make([]string, 0, len(entries))
 
 	for _, entry := range entries {
 		if entry.IsDir() {