Function buildPreviewDocument

packages/runtime/src/index.ts:595–624

(
  userSource: string,
  opts: BuildPreviewDocumentOptions = {},
)

}

export function buildPreviewDocument(
  userSource: string,
  opts: BuildPreviewDocumentOptions = {},
): string {
  const stripped = removeCspMetaTags(userSource);
  // Already-wrapped srcdoc (round-trip safe). When the workspace preview path
  // supplies a base URL, inject it once so relative assets still resolve.
  if (stripped.includes(JSX_TEMPLATE_BEGIN)) {
    return injectBaseHrefIntoHtmlDocument(stripped, opts.baseHref);
  }

  const classified = classifyRenderableSource(stripped, opts.path);
  const kind = classified === 'unknown' && opts.path === undefined ? 'jsx' : classified;
  if (kind === 'unknown') {
    throw new Error(`Unsupported preview file type: ${opts.path ?? 'unknown'}`);
  }

  if (kind === 'html') {
    const withRuntime = needsJsxRuntimeInHtml(stripped)
      ? injectJsxRuntimeIntoHtml(stripped)
      : stripped;
    return injectOverlayIntoHtmlDocument(
      injectPreviewViewportSupportIntoHtmlDocument(
        injectBaseHrefIntoHtmlDocument(withRuntime, opts.baseHref),
      ),
    );
  }

  return wrapJsxAsSrcdoc(stripped, { kind, baseHref: opts.baseHref });
}

function ensureStandaloneShell(html: string): string {
  const trimmed = html.trim();