What causes "Input can not be empty" in siyuan-note/siyuan?

Pass a non-empty tag name containing letters/digits to TagSnapshot

Input can not be empty

Error message

Input can not be empty

What it means

TagSnapshot validates the user-supplied tag name: after removing invalid characters (util.RemoveInvalid) and trimming spaces, an empty string yields errors.New(Conf.Language(142)) ('Input can not be empty'). The check exists because an empty tag name cannot identify a snapshot tag in the encrypted index.

Solutions

Pass a non-empty tag name containing letters/digits to TagSnapshot
Sanitize the input yourself before calling: strip invalid characters, trim, and reject empty results client-side with a clear prompt
If the desired name collapses to empty after sanitization, choose a different name — do not retry with the same value
Check Conf.Language(142) text in the error to distinguish this validation failure from the repo-key (Language 26) and symbol (Language 151) errors

Example fix

// before
name := docTitle // may be "---" or "   "
model.TagSnapshot(id, name)
// after
name := util.RemoveInvalid(docTitle)
name = strings.TrimSpace(name)
if name == "" {
    return errors.New("snapshot tag name can not be empty")
}
model.TagSnapshot(id, name)

Defensive patterns

Strategy: validation

Validate before calling

function validateTagName(raw) {
  const name = raw.replace(/[\\/:*?"'<>|]/g, '').trim();
  if (!name) throw new Error('Snapshot tag name can not be empty');
  return name;
}

Try / catch

try {
    await fetchPost('/api/repo/tagSnapshot', {id, name});
} catch (e) {
    if (e.msg === 'Input can not be empty') focusNameInputWithPrompt();
}

Prevention

Trim and sanitize the tag name in the UI before submission
Reject inputs that consist only of symbols or whitespace with an inline message
Do not derive tag names from titles that may be entirely punctuation without a fallback name
Test with edge-case inputs (spaces only, symbols only, empty string)

When it happens

Trigger: Calling TagSnapshot with a name consisting only of characters stripped by util.RemoveInvalid (e.g. symbols, path separators) or only whitespace, so the sanitized name becomes "" and the Language 142 error is returned.

Common situations: Frontend submits an empty tag input; automation passes a name built from a title that is entirely punctuation; whitespace-only name from a form that only trim-checks client-side after the kernel already stripped symbols.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

AI-assisted analysis of siyuan-note/siyuan@9f775e8a12 (2026-09-19). Data as JSON: /api/errors/4117c031e12b43df. Report an issue: GitHub.

Appendix: source

Thrown at kernel/model/repository.go:1728

		return
	}

	err = repo.RemoveTag(tag)
	return
}

func TagSnapshot(id, name string) (err error) {
	assetDownloadSourceMu.RLock()
	defer assetDownloadSourceMu.RUnlock()
	if 1 > len(Conf.Repo.Key) {
		err = errors.New(Conf.Language(26))
		return
	}

	name = util.RemoveInvalid(name)
	name = strings.TrimSpace(name)
	if "" == name {
		err = errors.New(Conf.Language(142))
		return
	}

	if !gulu.File.IsValidFilename(name) {
		err = errors.New(Conf.Language(151))
		return
	}

	repo, err := newRepositoryWithAssetSourceLocked()
	if err != nil {
		return
	}

	index, err := repo.GetIndex(id)
	if err != nil {
		return
	}

View on GitHub (pinned to 9f775e8a12)