dotnet/AspNetCore.Docs · error · Error

Must provide a non-empty value for the "src" attribute.

Error message

Must provide a non-empty value for the "src" attribute.

What it means

JavaScript guard throw inside registerPageScriptElement: if the 'src' argument is falsy (undefined, empty string, null) it throws because the page-script reference-counting map keys modules by src and cannot register an entry without a unique script URL. Used by the Blazor PageScript custom element helper that manages JS modules across navigations.

Source

Thrown at aspnetcore/blazor/includes/js-interop/blazor-page-script.md:6

```javascript
const pageScriptInfoBySrc = new Map();

function registerPageScriptElement(src) {
  if (!src) {
    throw new Error('Must provide a non-empty value for the "src" attribute.');
  }

  let pageScriptInfo = pageScriptInfoBySrc.get(src);

  if (pageScriptInfo) {
    pageScriptInfo.referenceCount++;
  } else {
    pageScriptInfo = { referenceCount: 1, module: null };
    pageScriptInfoBySrc.set(src, pageScriptInfo);
    initializePageScriptModule(src, pageScriptInfo);
  }
}

function unregisterPageScriptElement(src) {
  if (!src) {
    return;
  }

View on GitHub (pinned to c67a80103a)

Solutions

1. Always supply a non-empty, resolvable script path on the PageScript src attribute.
2. Validate src before binding: only render the PageScript element when the URL is present.
3. Default src to a known module path when configuration is absent.
4. Add a unit/runtime assertion that src is a non-empty string before calling register.

Example fix

// before
function registerPageScriptElement(src) {
  if (!src) {
    throw new Error('Must provide a non-empty value for the "src" attribute.');
  }
  // ...
}

// after — caller-side guard before rendering the element
@if (!string.IsNullOrWhiteSpace(ScriptSrc))
{
    <PageScript Src="@ScriptSrc" />
}
else
{
    <div class="text-warning">Script source not configured.</div>
}

// Guard before calling register
if (typeof src !== 'string' || src.trim() === '') {
  console.warn('PageScript src is empty; skipping registration.');
  return;
}

function isValidSrc(src) { return typeof src === 'string' && src.trim().length > 0; }

try { registerPageScriptElement(src); }
catch (e) {
  console.error('Failed to register page script:', e.message);
}

When it happens

Trigger: A <script type="text/javascript" src=""> or a PageScript element whose src attribute resolves to empty; calling registerPageScriptElement('') programmatically; an attribute binding that evaluates to undefined at render time.

Common situations: Dynamic src binding in a Razor template that is sometimes empty; copy/paste of the PageScript element with the src omitted; build/bundler stripping the src; attribute set from a configuration value that is missing.

Related errors

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AI-assisted analysis of dotnet/AspNetCore.Docs@c67a80103a (2026-08-13). Data as JSON: /api/errors/f20f953f3ca69657. Report an issue: GitHub.