Unfortunately, simple URL parsing breaks on so many things. There is a reason on why every URL parsing library is at least a few thousand LOCs.

One common way to test it is just to pass ipv6 url: http://[f021:d981:b487:e57d:193e:550e::]/

▲ meindnoch 21 hours ago | parent | next [-]

Is that so?

RFC 3986 Appendix B [1] "Parsing a URI Reference with a Regular Expression":

The following line is the regular expression for breaking-down a well-formed URI reference into its components.

  ^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?

      scheme    = $2
      authority = $4
      path      = $5
      query     = $7
      fragment  = $9

Let's test your URI with this regex, shall we? [2]

  $2 (scheme) = http
  $4 (authority) = [f021:d981:b487:e57d:193e:550e::]
  $5 (path) = /

Seems correct to me.

[1] https://datatracker.ietf.org/doc/html/rfc3986#appendix-B

[2] https://regexr.com/8nqop

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quuxplusone 20 hours ago | parent | next [-]

Hm, but I think he's right. The problem comes when you try to break down the authority portion into host and port; TFA's parser treats the first colon as introducing the port, which is wrong.

https://github.com/bkaradzic/bx/blob/0b001f5f36579e8aea07efa...

	▲	meindnoch 20 hours ago \| parent [-]
		>The problem comes when you try to break down the authority portion into host and port That's a problem orthogonal to URI parsing. You parse the URI with the RFC 3986 regex, which gives you the components: scheme, authority, path, query, fragment. You're then free to parse any of the components according to your own bespoke rules, e.g. the query string often follows the key=value&key=value&... pattern.

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afiori 17 hours ago | parent | prev | next [-]

> well-formed URI

A parser that assumes the input to be already valid is usually not enough for most applications

according to that regex this is a valid url

__..__..%%%zz..

	▲	meindnoch 14 hours ago \| parent [-]
		>according to that regex this is a valid url >__..__..%%%zz.. Correctly. It is a valid relative URI, whose path is "__..__..%%%zz..".

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f311a 17 hours ago | parent | prev [-]

Regexes are pretty slow, though.

	▲	meindnoch 14 hours ago \| parent [-]
		cc @burntsushi

▲ r3d 20 hours ago | parent | prev [-]

Yeah it's complicated, and that's the thing about parsing anything, the more complicated and unpredictable the input and the harder it is to parse.

Does it need to be human readable, does it need to work across all platforms. Does the it need to be secure. These things change everything. Speed, reliability, security pick one.

Your point about being compliant with the real spec is the difference between a 20 line scannf and and a 1000 line function. Yeah. Ha.