What causes "draft raw EML is empty" in larksuite/cli?

Populate the raw string with the base64url-encoded EML from the mail API response before calling Parse

draft raw EML is empty

Error message

draft raw EML is empty

What it means

decodeRawEML validates the base64url-encoded EML string passed to Parse before decoding. This error means the caller supplied an empty (or whitespace-only) raw string, so there is nothing to decode into a draft EML document. The parser refuses early instead of producing a confusing downstream parse failure.

Source

Thrown at shortcuts/mail/draft/parse.go:49

	snapshot := &DraftSnapshot{
		DraftID: raw.DraftID,
		Headers: headers,
		Body:    root,
	}
	if err := refreshSnapshot(snapshot); err != nil {
		return nil, err
	}
	return snapshot, nil
}

// maxRawEMLSize is the maximum accepted raw (base64-encoded) EML string length.
// Base64 encodes 3 bytes into 4 chars, so 35 MB covers a 25 MB decoded EML with margin.
const maxRawEMLSize = 35 * 1024 * 1024

func decodeRawEML(raw string) ([]byte, error) {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return nil, fmt.Errorf("draft raw EML is empty")
	}
	if len(raw) > maxRawEMLSize {
		return nil, fmt.Errorf("draft raw EML is too large (%d bytes, max %d)", len(raw), maxRawEMLSize)
	}
	decoders := []func(string) ([]byte, error){
		base64.URLEncoding.DecodeString,
		base64.RawURLEncoding.DecodeString,
		base64.StdEncoding.DecodeString,
		base64.RawStdEncoding.DecodeString,
	}
	for _, decode := range decoders {
		decoded, err := decode(raw)
		if err == nil {
			return normalizeLineEndings(decoded), nil
		}
	}
	return nil, fmt.Errorf("draft raw EML is not valid base64url")
}

View on GitHub (pinned to 7fd6ef3c07)

Solutions

Populate the raw string with the base64url-encoded EML from the mail API response before calling Parse
Check the field you are passing is the raw EML (e.g. body.Raw or similar), not an unrelated empty string field
Guard the call site: skip Parse or return a clearer error when the source draft has no raw content

Example fix

// before
part, err := draft.Parse(draft.Raw)
// after
if draft.Raw == "" {
    return fmt.Errorf("draft %s has no raw EML to parse", draft.ID)
}
part, err := draft.Parse(draft.Raw)

Defensive patterns

Strategy: validation

Validate before calling

if strings.TrimSpace(rawEML) == "" {
    return errors.New("no raw EML content: fetch the draft body before parsing")
}

Try / catch

part, err := draft.Parse(rawEML)
if err != nil && strings.Contains(err.Error(), "draft raw EML is empty") {
    // recover by re-fetching the draft raw content, then retry once
}

Prevention

Fetch raw EML content in the same code path that calls Parse
Never pass optional/zero-valued string fields directly into Parse
Trim inputs at the boundary so intent (empty vs whitespace) is explicit

When it happens

Trigger: Calling Parse with raw == "" or a string containing only whitespace (TrimSpace empties it); typically the draft's raw EML field was never fetched or a variable was left zero-valued.

Common situations: Fetching a draft whose body is empty/unsaved, forgetting to populate the raw EML field from a Lark mail API response before parsing, wiring the wrong struct field, or reading an empty file/env var into the raw string.

Related errors

AI-assisted analysis of larksuite/cli@7fd6ef3c07 (2026-09-04). Data as JSON: /api/errors/be406d3a38844ab7. Report an issue: GitHub.