siyuan-note/siyuan · error

Field [assets. ] should be of type [Object]

Error message

Field [assets.%d] should be of type [Object]

What it means

Each element of the assets array in /api/clipboard/prepareRichText must be a JSON object. This error fires when an element fails to unmarshal into an object (e.g. it is a string, number, or array) or unmarshals to a nil map.

Solutions

1. Send each asset as an object with at least a non-negative integer index and a non-empty string path
2. Validate the payload shape before sending (typeof item === 'object' && !Array.isArray(item))
3. Check for double JSON encoding — a JSON-stringified object inside the array will arrive as a string

Example fix

// before
{assets: ["/assets/foo.png"]}
// after
{assets: [{index: 0, path: "/assets/foo.png"}]}

assets.forEach((a, i) => { if (typeof a !== 'object' || a === null || Array.isArray(a)) throw new Error(`assets[${i}] must be an object`); });

const isAssetObject = (a) => typeof a === 'object' && a !== null && !Array.isArray(a);

When it happens

Trigger: Sending assets: ["foo"], [123], [[]], or [null] to /api/clipboard/prepareRichText instead of an array of objects like [{"index":0,"path":"..."}].

Common situations: Serializing asset IDs/paths directly instead of asset objects; a JSON producer double-encoding assets as strings; mixing old string-based asset payloads with the newer object schema after an API version change.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• Field [assets. .box] should be of type [String]
• Field [groups. ] should be of type [String]
• attr must be a string or null (got %T)
• block [ ] type is locked: expected , got
• createDocTree definition must be a list

AI-assisted analysis of siyuan-note/siyuan@9f775e8a12 (2026-09-19). Data as JSON: /api/errors/76c7ebeff1303ed1. Report an issue: GitHub.

Appendix: source

Thrown at kernel/apicontract/clipboard_input.go:28

func init() {
	PrepareRichText.decodeRequest = func(reader io.Reader) (request PrepareRichTextRequest, err error) {
		fields, err := blockRequestFields(reader, "/api/clipboard/prepareRichText")
		if err != nil {
			return request, err
		}
		assets, err := legacyField[[]json.RawMessage](fields, "assets", "Array", true)
		if err != nil {
			return request, err
		}
		if len(assets) == 0 {
			return request, fmt.Errorf("Field [assets] must not be empty")
		}
		request.Assets = make([]RichClipboardAsset, 0, len(assets))
		for i, raw := range assets {
			var asset map[string]json.RawMessage
			if json.Unmarshal(raw, &asset) != nil || asset == nil {
				return request, fmt.Errorf("Field [assets.%d] should be of type [Object]", i)
			}
			var index float64
			var path, box string
			if bytes.Equal(asset["index"], []byte("null")) || json.Unmarshal(asset["index"], &index) != nil || index < 0 || index != float64(int(index)) || json.Unmarshal(asset["path"], &path) != nil || strings.TrimSpace(path) == "" {
				return request, fmt.Errorf("Invalid rich clipboard asset at index [%d]", i)
			}
			if value, exists := asset["box"]; exists {
				if bytes.Equal(value, []byte("null")) || json.Unmarshal(value, &box) != nil {
					return request, fmt.Errorf("Field [assets.%d.box] should be of type [String]", i)
				}
			}
			request.Assets = append(request.Assets, RichClipboardAsset{Index: int(index), Path: strings.TrimSpace(path), Box: strings.TrimSpace(box)})
		}
		return
	}
	CleanupRichText.decodeRequest = func(reader io.Reader) (request CleanupRichTextRequest, err error) {
		fields, err := blockRequestFields(reader, "/api/clipboard/cleanupRichText")
		if err != nil {

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