fix: handle null/empty sources in source maps

[danielroe]

UPDATE: issue was produced by @nuxtjs/composition-api-plugin incorrectly producing a sourcemap. Will address in there but it might be worth still handling an empty source.

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Description

This PR updates the sourcemap support in vite to handle empty strings.

The issue I'm facing is the following error:

[vite] Internal server error: EISDIR: illegal operation on a directory, read

It is produced by attempting to read a directory path: sourceRoot + an empty sourcePath (= '').

Alternative solutions

We could just filter sources first for non-empty strings.

What is the purpose of this pull request?

• Bug fix

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[patak-dev]

I think it may be better to filter sources first as you proposed as an alternative, the file path in map.file may not be related to a source, no?

[patak-dev]

Thanks for the PR @danielroe. I was thinking, do you believe it would be useful to log a warning in these cases? Since the original error helped you found an issue in nuxt source maps, that may have been harder to see if it fails silently.

[danielroe]

@patak-js Yes, the error message could be something like Processing a sourcemap with no source filename. I imagine this would mostly be a library/dependency issue and hopefully would be caught in development of the library. Otherwise it might be a bit difficult to debug for a user.