feat(gatsby): write match-paths.json

[Moocar]

Description

Writes match-paths.json during pages writing. This file contains a map of matchPath -> path. It will be used by #13004 when finding pages in the production-app. See https://github.com/gatsbyjs/gatsby/pull/13004/files#diff-06ce5193de7c2c01dd947a5001c147c3R60 for how it's used.

Related Issues

• Sub-PR of [WIP] Replace global data.json with page-data.json per page #13004

[wardpeet]

I'm unsure about oldPage being set. Rest is looking good.

Do you have a small example how you'll be able to trigger oldPage.matchPath !== page.matchPath

[wardpeet]

fast returns are easier to read in my opinion

Suggested change

	if (page.matchPath) {
	if (!page.matchPath) {
	return state;
	}

[wardpeet]

I don't think oldPage is set on the action.

[pieh]

In pages-writer.js we do iterate over pages redux substate anyway, so it might be easier to generate derivative matchPaths from it? So we don't have to have 2 reducers reacting to CREATE_PAGE/DELETE_PAGE?

I.e:

- let { program, jsonDataPaths, pages, matchPaths } = store.getState()
+ let { program, jsonDataPaths, pages } = store.getState()
  pages = [...pages.values()]
+ const matchPaths = {}

  const pagesComponentDependencies = {}

  // Write out pages.json
  let pagesData = []
  pages.forEach(({ path, matchPath, componentChunkName, jsonName }) => {
    const pageComponentsChunkNames = {
      componentChunkName,
    }

    if (program._[0] === `develop`) {
      pagesComponentDependencies[path] = pageComponentsChunkNames
    }

    pagesData.push({
      ...pageComponentsChunkNames,
      jsonName,
      path,
      matchPath,
    })
+
+   if (matchPath) {
+     matchPaths[matchPath] = path
+   }
  })

[Moocar]

Apologies, this was a sloppy PR. The match-paths reducer was necessary in incremental build land, which this work originated from. But I never went back and de-incrementalized it. @pieh I like your suggestion. It's much clearer. I'll implement that now

[Moocar]

Fixed in 966f035

[pieh]

👍