feat(gatsby-plugin-manifest): Update manifest on navigation

[namukang]

Description

With the addition of the localize option in gatsby-plugin-manifest (#13471), multiple manifests can be generated and served depending on the path of the URL. While the correct manifest is served on initial page load, the link to the manifest is never updated even if the user navigates to a page that should include a different manifest.

This PR hooks into onRouteChange in gatsby-browser.js in order to update the manifest as necessary.

Related Issues

Fixes #17255

[namukang]

Hm, not sure why the e2e test is failing since I use the asset prefix when setting the manifest: https://github.com/gatsbyjs/gatsby/pull/17426/files#diff-9d857a76b97041cf4aefbf1950cd3c9fR11

[namukang]

Hoping I can also get some help regarding this ESLint warning I get when working on the plugin as a local plugin:

Module Warning (from ./node_modules/eslint-loader/index.js):

/Users/dskang/Code/dkthehuman.com/plugins/gatsby-plugin-manifest-multiple/gatsby-browser.js
  1:1  warning  'use strict' is unnecessary inside of modules  strict

Babel adds "use strict" to the top of every file and ESLint (I'm using Gatsby's default config) complains about it. Have you encountered this before when working on plugins as a local plugin?

Update: I filed a separate issue with a test repo to demonstrate the problem: #17489

[wardpeet]

I'm pretty confident that this is ready to be shipped.

• fixed default localized manifest & sw support (gatsby-plugin-offline wasn't caching the correct file)
• Only add gatsby-browser code when necessary

I think we can iterate on this if the startWith/regex doesn't suffice.

Maybe you have some final comments @moonmeister

[wardpeet]

@moonmeister, yeah offline plugin has issues with it. I think it's good to just keep the default one manifest.webmanifest and only suffix the ones that are in the localized string.

Thanks for pointing out gatsby-ssr, I forgot about it and looks like I didn't have any issue because of rehydration XD.

The latest offline plugin doesn't prefetch manifest anymore when it's not found so the issue looks like it doesn't exist anymore. I'll bring that feature back as it's a regression.

I updated tests and I think, it's ready to go.

[moonmeister]

What about caching the non-default manifests?

[wardpeet]

They will be cached when navigating. I'll fix the regression of manifest prefetching on first load in gatsby-plugin-offline but it's not a problem of this PR

[wardpeet]

Let's ship this. Thanks @dkthehuman & @moonmeister