Describe the bug

Path literals in the Nix language do not support ~ characters within the path (apart from the first character). However, such characters may occur in valid paths.

Steps To Reproduce

1. Open nix repl
2. Enter ./foo~
3. Observe error: syntax error, unexpected invalid token, expecting end of file.

Expected behavior

Nix accepts path literals containing ~ characters in other positions than the beginning as legal paths.

nix-env --version output

nix (Nix) 2.11.1

Additional context

This is about ~ in locations other than the very beginning of the literal, where in stands for $HOME, ~/foo is accepted by Nix 2.11.1 and resolves to the same path as $HOME/foo.

Possible workarounds thanks to @thufschmitt and @shlevy:

./${"foo~"}
./. + "/foo~"

Possibly relevant part of the code thanks to @layus.

The issue occurs in the Bazel extension rules_nixpkgs in the context of nixopts location expansion when expanding labels to external workspaces in the new bzlmod dependency system. In that case the workspace directory is defined by the mangled name of the external workspace which includes ~ characters, e.g. external/nixpkgs_location_expansion_test_file~override/test_file for @nixpkgs_location_expansion_test_file//:test_file. The above workaround would have to be performed by users of rules_nixpkgs, meaning the issue is user-facing for rules_nixpkgs.

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