Write only the document to stdout from snapshot remove --json (closes #251)

When the destination store cannot be reached, `snapshot remove` still
removes the snapshot from the local index and warns. The warning went
through the UI, which writes to stdout, so under `--json` it landed
ahead of the document and `| jq` failed on a command that exited 0.
Under `--json` the UI warning is now skipped. The logger's warning,
which goes to stderr in every mode, now also says to run `vaultik
prune` once the destination store is reachable.

The new test runs the command through `Entry` against a missing
destination directory, decodes stdout as exactly one JSON document, and
finds the warning and the `vaultik prune` follow-up on stderr.

Model: opus-5-5

internal/cli/entry_stdout_stderr_test.go

@@ -87,12 +87,31 @@ func TestEntryJSONFailureIsReportedOnStderr(t *testing.T) {
 	}
 }
 
-// writeUnusableDestinationConfig builds a config whose destination
-// directory does not exist, which fails `remote info`, and whose local
-// index is bound to another destination, which fails `prune` and
-// `snapshot remove` (a missing destination alone only makes `snapshot
-// remove` warn). Returns the config path.
-func writeUnusableDestinationConfig(t *testing.T) string {
+// TestEntrySnapshotRemoveJSONWarningIsOnStderr runs `snapshot remove
+// --json` against a destination directory that does not exist. The
+// command still exits 0 after removing the snapshot from the local
+// index. Its stdout must hold the document alone, with the warning
+// about the destination store, and the `vaultik prune` follow-up, on
+// stderr.
+//
+//nolint:paralleltest // replaces os.Args, os.Stdout, os.Stderr and the xdg globals
+func TestEntrySnapshotRemoveJSONWarningIsOnStderr(t *testing.T) {
+	configPath, _ := writeMissingDestinationConfig(t)
+
+	code, stdout, stderr := runEntry(t, flagConfig, configPath,
+		cmdSnapshot, cmdRemove, someSnapshotID, flagJSON)
+
+	require.Equal(t, 0, code)
+	requireExactlyOneJSONDocument(t, stdout)
+	assert.Contains(t, stderr,
+		"Could not remove snapshot metadata from remote storage")
+	assert.Contains(t, stderr, "run 'vaultik prune'")
+}
+
+// writeMissingDestinationConfig builds a config whose destination
+// directory does not exist. Returns the config path and the path of
+// its local index, which is not created here.
+func writeMissingDestinationConfig(t *testing.T) (string, string) {
 	t.Helper()
 
 	dir := t.TempDir()
@@ -114,6 +133,19 @@ func writeUnusableDestinationConfig(t *testing.T) string {
 	xdg.Reload()
 	t.Cleanup(xdg.Reload)
 
+	return configPath, indexPath
+}
+
+// writeUnusableDestinationConfig builds a config whose destination
+// directory does not exist, which fails `remote info`, and whose local
+// index is bound to another destination, which fails `prune` and
+// `snapshot remove` (a missing destination alone only makes `snapshot
+// remove` warn). Returns the config path.
+func writeUnusableDestinationConfig(t *testing.T) string {
+	t.Helper()
+
+	configPath, indexPath := writeMissingDestinationConfig(t)
+
 	ctx := context.Background()
 
 	db, err := database.New(ctx, indexPath)
@@ -122,7 +154,7 @@ func writeUnusableDestinationConfig(t *testing.T) string {
 	defer func() { require.NoError(t, db.Close()) }()
 
 	require.NoError(t, database.NewRepositories(db).LocalMeta.Set(ctx,
-		database.LocalMetaKeyStorageURL, "file://"+filepath.Join(dir, "other")))
+		database.LocalMetaKeyStorageURL, "file://"+t.TempDir()))
 
 	return configPath
 }

internal/vaultik/snapshot.go

@@ -1167,7 +1167,7 @@ func (v *Vaultik) RemoveSnapshot(
 	}
 
 	if !opts.LocalOnly {
-		result.RemoteRemoved = v.removeSnapshotRemote(snapshotID)
+		result.RemoteRemoved = v.removeSnapshotRemote(snapshotID, opts)
 	}
 
 	if v.SnapshotManager != nil {
@@ -1252,7 +1252,7 @@ func (v *Vaultik) confirmRemoveSnapshot(snapshotID string, opts *RemoveOptions)
 // removal has already happened, so the user is told the remote half
 // didn't finish and can retry with `vaultik prune` once the destination
 // store is reachable. Returns true when the remote removal succeeded.
-func (v *Vaultik) removeSnapshotRemote(snapshotID string) bool {
+func (v *Vaultik) removeSnapshotRemote(snapshotID string, opts *RemoveOptions) bool {
 	log.Info("Removing snapshot metadata from remote storage",
 		"snapshot_id", snapshotID)
 
@@ -1260,10 +1260,13 @@ func (v *Vaultik) removeSnapshotRemote(snapshotID string) bool {
 
 	err := v.deleteRemoteSnapshotByKey(remoteKey)
 	if err != nil {
-		log.Warn("Could not remove snapshot metadata from remote storage",
-			"error", err)
+		log.Warn("Could not remove snapshot metadata from remote storage; "+
+			"run '"+pruneCommandHint+"' once the remote is reachable "+
+			"to finish cleanup", "error", err)
 
-		if v.UI != nil {
+		// The UI writes to stdout, which under --json holds only the
+		// document; the log record above is the warning on stderr.
+		if v.UI != nil && !opts.JSON {
 			v.UI.Warningf("Could not remove snapshot metadata from remote: "+
 				"%v. Run '%s' once the remote is reachable to finish cleanup.",
 				err, pruneCommandHint)