octobercms/october · error · Error

Inspector title is a required string

Error message

Inspector title is a required string

What it means

InspectorHost.showModal() opens the Inspector modal and validates every argument up front; the first check requires a non-empty string `title`, which becomes the modal heading. A missing, non-string, or empty title throws synchronously before any UI is mounted — a nameless modal is always a caller bug, not a runtime condition.

Source

Thrown at modules/backend/vuecomponents/inspector/assets/js/classes/host.js:4

export class InspectorHost {
    showModal(title, obj, dataSchema, uniqueId, options, parentObj) {
        if (typeof title !== 'string' || !title.length) {
            throw new Error('Inspector title is a required string');
        }

        if (typeof obj !== 'object') {
            throw new Error('Inspector Object must be an object');
        }

        if (parentObj !== undefined && typeof parentObj !== 'object') {
            throw new Error('Inspector Parent Object must be an object');
        }

        if (!Array.isArray(dataSchema)) {
            throw new Error('Inspector data schema must be an array');
        }

        if (typeof uniqueId !== 'string' || !uniqueId.length) {
            throw new Error('Inspector unique key is a required string');
        }

View on GitHub (pinned to b608633a7e)

Solutions

1. Pass a non-empty string as the first argument.
2. Default computed titles: showModal(title || 'Properties', ...).
3. If the title comes from localization, fix or fall back for the missing translation key.

Example fix

// before
host.showModal(this.config.title, obj, schema, uniqueId);

// after
host.showModal(this.config.title || 'Properties', obj, schema, uniqueId);

const modalTitle = typeof title === 'string' && title.length ? title : 'Properties';
host.showModal(modalTitle, obj, schema, uniqueId);

function isInspectorTitle(value) {
    return typeof value === 'string' && value.length > 0;
}

When it happens

Trigger: Calling showModal(undefined, obj, schema, id) or showModal('', obj, schema, id) — e.g. a config-driven title key that is absent, a translation key that resolved to empty, or arguments passed in the wrong order.

Common situations: Custom plugin JavaScript opening the inspector modal programmatically; refactoring from an inline inspector (where the title lives in the schema) to showModal and forgetting the now-explicit title argument; data-driven UIs where the title element is optional.

Understand the failure class

Background: Invalid argument type errors: "must be of type string", "expected X, got Y", and ERR_INVALID_ARG_TYPE explained — this error's family across 15 libraries.

Related errors

• Inspector Object must be an object
• Inspector Parent Object must be an object
• Inspector data schema must be an array
• Inspector unique key is a required string
• getDynamicOptionsExtraData must return an object

AI-assisted analysis of octobercms/october@b608633a7e (2026-08-21). Data as JSON: /api/errors/ebcb40d683d065cb. Report an issue: GitHub.