eliminate SSR page instantiation during graph lifecycle

[thescientist13]

Overview

In order to build a graph of all pages, Greenwood gets the metadata of SSR based pages, calling functions like getFrontmatter or reading page level configurations like prerender or isolation.

However the SSR route worker is not efficient as it could be since, it will just automatically run all the things, including just blindly generating the page using WCC

async function executeRouteModule({ modulePath, compilation, route, label, id, prerender, htmlContents, scripts }) {
  const parsedCompilation = JSON.parse(compilation);
  const data = {
    template: null,
    body: null,
    frontmatter: null,
    html: null
  };

  if (prerender) {
    ...
  } else {
    const module = await import(pathToFileURL(modulePath)).then(module => module);
    const { getTemplate = null, getBody = null, getFrontmatter = null } = module;

    if (module.default) {
      const { html } = await renderToString(pathToFileURL(modulePath));

      data.body = html;
    } else {
      if (getBody) {
        data.body = await getBody(parsedCompilation, route);
      }
    }

    if (getTemplate) {
      data.template = await getTemplate(parsedCompilation, route);
    }

    if (getFrontmatter) {
      data.frontmatter = await getFrontmatter(parsedCompilation, route, label, id);
    }
  }

  parentPort.postMessage(data);
}

executeRouteModule(workerData);

Details

Basically, all your pages will get alllllllll those functions called, making your API requests, etc. Just for building the graph, nothing other than frontmatter is needed. All this stuff will get built anyone during the build so this is just duplicate / wasted effort.

This is related to some other issues as well

• I imagine this will help contribute to improving performance benchmarking / optimizing Greenwood #970
• I think we might want to rethink templates and pages and maybe clean up some of these APIs - Layouts (Templates) and Pages #955
• Might make sense to do in tandem with warnings emitted about undefined page level custom element tags when pre-rendering SSR pages #988

How do we account for options coming out of a page though?
#1206

export const isolation = true;

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So we'll definitely want to think of a way to refactor this so develop is a no-op, and this only happens once on build.