Fix root directory resolution logic

[markdalgleish]

Fixes #12390

This PR fixes a few issues that were raised by the issue linked above:

• When providing a custom Vite config via the CLI (e.g. react-router dev --config apps/my-app/vite.config.ts), the React Router project directory would still be cwd. This meant that you'd get an error about a missing root route even if it's present in the directory containing the Vite config. To fix this, if a custom Vite config path is provided, we now default the React Router project root to be the directory containing the custom Vite config.
• The logic for resolving the project root directory was duplicated across different commands. This PR introduces a resolveRootDirectory util which is used consistently across all commands. This gives us a central place to implement the fix mentioned above. This issue wasn't explicitly raised, but was highlighted when fixing the above issue.
• When your React Router root directory doesn't contain a package.json but a parent directory has one, an error is thrown because we try to read the non-existent package.json from root. To fix this, we now also walk parent directories to find package.json. If none of the parent directories contain a package.json, you'll still see the same error as before.

Note that I've opted not to test this logic specifically. I've manually tested in one of our playgrounds, moving all app code into a subdirectory and ensuring I can do the following:

• Run with a custom root, e.g. react-router dev apps/my-app.
• Run with a custom Vite config in a root directory, e.g. react-router dev --config apps/my-app/vite.config.ts

I've also tried to ensure this doesn't break any usages that inadvertently work today (e.g. having config files in a config dir and the app directory in the root), but this just showed me that too much of our code assumes everything is in the root directory. If the Vite config is in a config dir, a react-router.config.ts file next to it doesn't get picked up. In this scenario, we also generate a .react-router dir in the config dir. This makes me much more confident that it's safe to infer the root directory from the Vite config location since it currently doesn't seem to work otherwise.

[changeset-bot]

🦋 Changeset detected

Latest commit: 1d760f6

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 11 packages

Name	Type
@react-router/dev	Patch
@react-router/fs-routes	Patch
@react-router/remix-routes-option-adapter	Patch
create-react-router	Patch
react-router	Patch
react-router-dom	Patch
@react-router/architect	Patch
@react-router/cloudflare	Patch
@react-router/express	Patch
@react-router/node	Patch
@react-router/serve	Patch

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[markdalgleish]

@pcattori Just calling out that since the --config flag impacts the project root directory (and hence where routes live etc.), I think it makes sense to support this in all CLI commands for consistency, even those that don't use the Vite config.

[markdalgleish]

Side note, but I think this raises something I might have missed when we introduced react-router.config.ts, which is that the --config flag probably should have been updated to point to our config, and any custom Vite config path should have been configured there, or via a separate --vite-config flag.

This is part of my rationale for this change. If our --config flag pointed to react-router.config.ts, I would want to support it here too.

[markdalgleish]

Note that if a root directory was explicitly provided (e.g. react-router build my/app/dir) this will still take precedence. We only fall back to inferring the root when this isn't provided, so anyone relying on this should maintain existing behaviour.

[github-actions]

🤖 Hello there,

We just published version 7.6.0 which includes this pull request. If you'd like to take it for a test run please try it out and let us know what you think!

Thanks!