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Duplicated prefetch link (with SSR)

See original GitHub issue

I’m creating a component chunk that needs to be prefetched. I’m rendering the prefetch link on SSR for component chunk through ChunkExtractorManager

// loadableComponents.js
const LoadableLibrary = loadable.lib(() => import(
  /* webpackChunkName: "component" */
  /* webpackPrefetch: true */
  'external-library',
));
export const ExampleComponent = props => (
  <LoadableLibrary>
    {({ default: Component }) => <Component {...props} />}
  </LoadableLibrary>
);

// renderer.js
const extractor = new ChunkExtractor({ statsFile, entrypoints: ['client'] });
const content = (
  <ChunkExtractorManager extractor={extractor}>
    { /* content management */ }
  </ChunkExtractorManager>
);
const linkTags = renderToStaticMarkup(extractor.getLinkElements());
return `
  <!DOCTYPE html>
  <html>
    <head>
      ${linkTags}
    </head>
    <body>
      <div id="root">${content}</div>
    </body>
    <!-- bundle script -->
  </html>
`;

After the client receives the template, and the browser evaluates my bundle.js, webpack runtime finds those dynamic imports and add again the prefetch link for script.js, causing:

duplicated prefetch link tags
another fired request for the same resource.

Is this the correct behavior? Am I missing something?

Issue Analytics

State:
Created 5 years ago
Comments:7 (3 by maintainers)

Top GitHub Comments

1reaction

aseem2625commented, May 17, 2019

Facing same issue. Most probably a webpack issue only. But very difficult to get a way around. In all cases I’m having extractor.getLinkTags() inserted in html

With prefetch magic comment

const Home = loadable (() => import(/* webpackChunkName: "home" */ /* webpackPrefetch: true */ 'views/Home'));

const People = loadable (() => import(/* webpackChunkName: "people" */ 'views/People'));

const UI = loadable (() => import(/* webpackChunkName: "ui" */ 'views/UI/UI'));

const NotFound = loadable (() => import(/* webpackChunkName: "404" */ /* webpackPrefetch: true */ 'views/NotFound'));

RED: loadable-components preloading the chunks.
GREEN: loadable-components also takes prefetch magic comment and inserts them as prefetch
BLUE: When main.js is loaded on client side, it again inserts the prefetch links.

Having preload magic comment instead of prefetch

Without any magic comment

Is there any way to figure this out, or otherwise manually can add prefetch links for desired routes based on their corresponding generated chunks. But that’s one ugly approach I wanted to keep for last ?

0reactions

gerhardslettencommented, Jun 19, 2020

Its also possible to filter out which files that should be listed for prefetch like this:

const srcFiles = extractor
    .getScriptElements()
    .map((item) => item.props.src)
    .filter(Boolean)
  // Filter out prefetch files allready loaded in scriptfiles
  const prefetchFilter = (item) =>
    !srcFiles.some((file) => file === item.props.href)
return (
<html lang={config.locale}>
      <head>
        {extractor.getLinkElements().filter(prefetchFilter)}
      </head>
</html>
)

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