Restart dev server on package.json changes

[matthewp]

Changes

• Adds the package.json to the list of watch files. We restart the dev container any time one of these files changes.
• This is needed to get sass to work when installed after the dev server has already been started.
• This now works in Vite 3.2.4
• Closes HMR: Installing sass when in error state does not reload page #5145

Testing

• Unit test added which confirms the dev server is restarted when the package.json changes.

Docs

N/A, bug fix

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[natemoo-re]

LGTM! One comment about being a bit more defensive.

[natemoo-re]

This seems like an odd edge case, but should we check if package.json exists first?

Since Deno is landing npm: support, I think we're not far off from an Astro project that doesn't have a package.json file being a feasible thing.

[matthewp]

We don't need to check for that. This is used that when a file does change and it matches one of the files in watchFiles, it will trigger a restart. If the file doesn't exist then it will never match. It doesn't cause some other process to try and read the (potentially not existing) files.

Here's the only place this information is used:

astro/packages/astro/src/core/dev/restart.ts

Lines 55 to 57 in 7191ed1

	shouldRestart = settings.watchFiles.some(
	(path) => vite.normalizePath(path) === vite.normalizePath(changedFile)
	);