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
already goes to stderr.

The new test runs the command through `Entry` against a missing
destination directory and decodes stdout as exactly one JSON document.

Judgement call: under `--json` the stderr warning is the log record,
which names the error but not the `vaultik prune` follow-up.

Model: opus-5-5

TODO.md

@@ -22,6 +22,14 @@ the tag exists and is exercised; what is left is merging `next` to
 
 # Completed Steps
 
+- 2026-10-06: Made `snapshot remove --json` write only its document to
+  stdout when the destination store cannot be reached
+  ([issue #251](https://git.eeqj.de/sneak/vaultik/issues/251)). Its
+  warning that the snapshot's metadata was left on the destination store
+  went to stdout ahead of the document, breaking `| jq` on a command that
+  exited 0. Under `--json` the warning now reaches stderr only, through
+  the logger.
+
 - 2026-10-06: Made command output follow the README's stdout and stderr
   rules ([issue #224](https://git.eeqj.de/sneak/vaultik/issues/224)). The
   startup banner went to stdout, so a `completion` script or a

internal/cli/entry_stdout_stderr_test.go

@@ -87,12 +87,29 @@ func TestEntryJSONFailureIsReportedOnStderr(t *testing.T) {
 	}
 }
 
-// writeUnusableDestinationConfig builds a config whose destination
+// TestEntrySnapshotRemoveJSONWarningIsOnStderr runs `snapshot remove
-// directory does not exist, which fails `remote info`, and whose local
+// --json` against a destination directory that does not exist. The
-// index is bound to another destination, which fails `prune` and
+// command still exits 0 after removing the snapshot from the local
-// `snapshot remove` (a missing destination alone only makes `snapshot
+// index. Its stdout must hold the document alone, with the warning
-// remove` warn). Returns the config path.
+// about the destination store on stderr.
-func writeUnusableDestinationConfig(t *testing.T) string {
+//
+//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")
+}
+
+// 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 +131,19 @@ 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 +152,7 @@ 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)
 
@@ -1263,7 +1263,9 @@ func (v *Vaultik) removeSnapshotRemote(snapshotID string) bool {
 		log.Warn("Could not remove snapshot metadata from remote storage",
 			"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)