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errno: io::Error to Errno conversion sugar #1155
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asomers
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For many of Nix's consumers it be convenient to easily convert a Nix error into a std::io::Error. That's currently not possible because of the InvalidPath, InvalidUtf8, and UnsupportedOperation types that have no equivalent in std::io::Error. However, very few of Nix's public APIs actually return those unusual errors. So a more useful API would be for Nix's standard error type to implement Into<std::io::Error>. This commit makes Error a simple NewType around Errno. For most functions it's a drop-in replacement. There are only three exceptions: * clearenv now returns a bespoke error type. It was the only Nix function whose error couldn't be cleanly mapped onto an Errno. * sys::signal::signal now returns Error(Errno::ENOTSUP) instead of Error::UnsupportedOperation when the user passes an incompatible argument to `handler`. * When a NixPath exceeds PATH_MAX, it will now return Error(Errno::ENAMETOOLONG) instead of Error::InvalidPath. In the latter two cases there is now some abiguity about whether the error code was generated by Nix or by the OS. But I think the ambiguity is worth it for the sake of being able to implement Into<io::Error>. This commit also introduces Error::Sys() as a migration aid. Previously that as an enum variant. Now it's a function, but it will work in many of the same contexts as the original. Fixes nix-rust#1155
asomers
added a commit
to asomers/nix
that referenced
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Jun 13, 2021
For many of Nix's consumers it be convenient to easily convert a Nix error into a std::io::Error. That's currently not possible because of the InvalidPath, InvalidUtf8, and UnsupportedOperation types that have no equivalent in std::io::Error. However, very few of Nix's public APIs actually return those unusual errors. So a more useful API would be for Nix's standard error type to implement Into<std::io::Error>. This commit makes Error a simple NewType around Errno. For most functions it's a drop-in replacement. There are only three exceptions: * clearenv now returns a bespoke error type. It was the only Nix function whose error couldn't be cleanly mapped onto an Errno. * sys::signal::signal now returns Error(Errno::ENOTSUP) instead of Error::UnsupportedOperation when the user passes an incompatible argument to `handler`. * When a NixPath exceeds PATH_MAX, it will now return Error(Errno::ENAMETOOLONG) instead of Error::InvalidPath. In the latter two cases there is now some abiguity about whether the error code was generated by Nix or by the OS. But I think the ambiguity is worth it for the sake of being able to implement Into<io::Error>. This commit also introduces Error::Sys() as a migration aid. Previously that as an enum variant. Now it's a function, but it will work in many of the same contexts as the original. Fixes nix-rust#1155
Thanks @asomers! 💚 |
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I'd like to have some conversion sugar to get an
nix::errno::Errno
from astd::io::Error
. That is, going in the opposite direction of #613.Strawman would be:
The use case is to improve ergonomics when pattern matching on stdlib results, like this:
Would something like this be welcome in
nix::errno
?The text was updated successfully, but these errors were encountered: