url: fix toPathIfFileUrl with string URL input

[AidanWelch]

Functions using toPathIfFileURL (such as fs.readdir) would have unexpected behavior when a string of a file URL was input such as import.meta.url, fileURLToPath supports string input so there is no reason to not convert file URL strings.

[nodejs-github-bot]

Review requested:

• @nodejs/url

[LiviaMedeiros]

@AidanWelch thank you for pull request!
However, I don't think we can change this, see #48994 for reference.

To use URLs with node:fs, user should pass URL object so it can be distinguished from path. For example, to read contents of directory where current file is located, use readdir(new URL('.', import.meta.url)) rather than readdir(new URL('.', import.meta.url).href).

If this looks unexpected, maybe you would want to update File URL paths part of documentation instead to explain it more clearly?

[AidanWelch]

I think it is unexpected because import actually does support URL strings, furthermore the conversion for URL to Path also supports URL strings. I don't see the point in the ambiguity of sometimes assuming string inputs are always paths and sometimes not, especially when it is a very trivial check,

[LiviaMedeiros]

import, url.fileURLToPath (and some other APIs such as Fetch API) accept URL but do not accept paths, hence there is no ambiguity for them.

Any API that uses toPathIfFileURL() function accepts paths as string and URLs as object. Urlstring can be interpreted as perfectly valid path that points on different location, so unless we drop pathstring support first, we can't accept urlstrings.

[AidanWelch]

Urlstring can be interpreted as perfectly valid path that points on different location, so unless we drop pathstring support first, we can't accept urlstrings.

How so?

[aduh95]

Urlstring can be interpreted as perfectly valid path that points on different location, so unless we drop pathstring support first, we can't accept urlstrings.

How so?

file:///dev/null can be parsed either as a relative path leading to ./file:/dev/null, or as an absolute URL leading to /dev/null. Node.js interprets it as the former for all the APIs that accept paths (e.g. fs.readdir), and as the latter for APIs that do not accept paths (e.g. fileURLToPath).