Function flexJSONToString

internal/models/item.go:755–806

flexJSONToString accepts a raw JSON value and returns it as a canonical JSON-encoded string. Acceptable inbound shapes: - absent / empty / null → nil (caller leaves the field unchanged) - JSON-encoded string whose INNER content is either empty (the legacy empty-string sentinel handled downstream by

(raw json.RawMessage, expectedStart byte, errInvalid error)

// is supposed to add. The pre-existing ItemUpdate fields/tags path
// inherits the same tightening because it routes through this helper.
func flexJSONToString(raw json.RawMessage, expectedStart byte, errInvalid error) (*string, error) {
	trimmed := bytes.TrimSpace(raw)
	if len(trimmed) == 0 || bytes.Equal(trimmed, []byte("null")) {
		return nil, nil
	}
	switch trimmed[0] {
	case '"':
		// JSON-encoded string envelope — unmarshal to the underlying Go
		// string and then validate the inner content's shape matches
		// expectedStart. Subsequent code that does
		// json.Unmarshal([]byte(*s), ...) sees the inner JSON, not a
		// re-quoted string.
		var s string
		if err := json.Unmarshal(trimmed, &s); err != nil {
			return nil, errInvalid
		}
		// Empty inner string is the empty-string sentinel; store-layer
		// coercion handles it (IDEA-1486). Don't reject here so callers
		// retain the legacy "" → default normalization shape.
		innerTrimmed := bytes.TrimSpace([]byte(s))
		if len(innerTrimmed) == 0 {
			return &s, nil
		}
		if innerTrimmed[0] != expectedStart {
			return nil, errInvalid
		}
		// Confirm the inner content actually parses as JSON of the
		// expected shape. Catches strings that start with the right
		// brace but are otherwise garbage (e.g. `"{not valid"`).
		var inner any
		if err := json.Unmarshal(innerTrimmed, &inner); err != nil {
			return nil, errInvalid
		}
		return &s, nil
	case expectedStart:
		// Object or array — re-marshal to a canonical JSON string so
		// the downstream string-typed pipeline can json.Unmarshal it
		// back to a map/slice exactly as if the caller had stringified.
		var v any
		if err := json.Unmarshal(trimmed, &v); err != nil {
			return nil, errInvalid
		}
		b, err := json.Marshal(v)
		if err != nil {
			return nil, errInvalid
		}
		s := string(b)
		return &s, nil
	default:
		return nil, errInvalid
	}
}

type ItemListParams struct {
	CollectionSlug  string