Cabal treats url with trailing whitespace in import cabal.project file as a file path

[theGhostJW]

Describe the bug

Cabal treats url with trailing whitespace in import cabal.project file as a file path

To Reproduce
Steps to reproduce the behavior:

When following along with: the users guide

1. Add the following to the cabal.project file:

packages: .
import: https://www.stackage.org/nightly-2024-12-05/cabal.config 

Note: there is a trailing space at the end of the url

$ cabal build .

=> An error similar to the following is emitted:

/home/john-walker/repos/pyrethrum/https:/www.stackage.org/nightly-2024-12-05/cabal.config : withBinaryFile: does not exist (No such file or directory)

3. delete the trailing white space.
4. try build again

$ cabal build .

=> build proceeds as expected

Expected behavior

The current behaviour is confusing if you don't notice the white space. A better UX would be to:

1. automatically trim the url OR
2. emit a specific error pertaining to the trailing space

System information

• Operating system: Ubuntu 24.04.1 LTS
• cabal: cabal 3.12.1.0
• ghc: GHC 9.8.4

[philderbeast]

I can reproduce this.

[philderbeast]

We're relying on Network.URI.parseURI:

$ cabal repl cabal-install
...
ghci> import Network.URI
ghci> parseURI "https://www.stackage.org/nightly-2024-12-05/cabal.config"
Just https://www.stackage.org/nightly-2024-12-05/cabal.config
ghci> parseURI "https://www.stackage.org/nightly-2024-12-05/cabal.config "
Nothing

[philderbeast]

A string is a valid URL potentially surrounded by spaces if, after stripping leading and trailing whitespace from it, it is a valid URL.
W3C/HTML5/URLs

[philderbeast]

I tested this on cabal-install versions; 3.8.1.0, 3.10.1.0, 3.10.2.0, 3.10.3.0 and 3.12.1.0. They all reported an error of "withBinaryFile: does not exist (No such file or directory)", something like this:

$ ~/.ghcup/bin/cabal build all --dry-run --project-file=cabal.tabs-and-spaces.project
/home/.../cabal/https://www.stackage.org/nightly-2024-12-05/cabal.config
: withBinaryFile: does not exist (No such file or directory)