feat(tvix/eval): Support builtins.tail
TL;DR: - support `builtins.tail` - define `ErrorKind::TailEmptyList` and canonical error code - support basic unit tests Unsure whether or not the error should be a dedicated `ErrorKind`... Change-Id: Iae90fda1bb21ce7bdb1aaa2aeb2b8c1e6dcb0f05 Reviewed-on: https://cl.tvl.fyi/c/depot/+/6545 Reviewed-by: wpcarro <wpcarro@gmail.com> Autosubmit: wpcarro <wpcarro@gmail.com> Reviewed-by: tazjin <tazjin@tvl.su> Tested-by: BuildkiteCI
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4 changed files with 21 additions and 0 deletions
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@ -221,6 +221,16 @@ fn pure_builtins() -> Vec<Builtin> {
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x.as_str()[(beg as usize)..(end as usize)].into(),
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))
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}),
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Builtin::new("tail", 1, |args, vm| {
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let xs = args[0].force(vm)?.to_list()?;
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if xs.len() == 0 {
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Err(ErrorKind::TailEmptyList)
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} else {
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let output = xs.into_iter().skip(1).collect::<Vec<_>>();
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Ok(Value::List(NixList::construct(output.len(), output)))
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}
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}),
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Builtin::new("throw", 1, |mut args, _| {
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return Err(ErrorKind::Throw(
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args.pop().unwrap().to_str()?.as_str().to_owned(),
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@ -31,6 +31,9 @@ pub enum ErrorKind {
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index: i64,
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},
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/// Attempted to call `builtins.tail` on an empty list.
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TailEmptyList,
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TypeError {
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expected: &'static str,
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actual: &'static str,
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@ -150,6 +153,8 @@ impl Error {
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format!("list index '{}' is out of bounds", index)
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}
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ErrorKind::TailEmptyList => format!("'tail' called on an empty list"),
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ErrorKind::TypeError { expected, actual } => format!(
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"expected value of type '{}', but found a '{}'",
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expected, actual
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@ -257,6 +262,7 @@ to a missing value in the attribute set(s) included via `with`."#,
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ErrorKind::NotAnAbsolutePath(_) => "E020",
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ErrorKind::ParseIntError(_) => "E021",
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ErrorKind::NegativeLength { .. } => "E022",
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ErrorKind::TailEmptyList { .. } => "E023",
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ErrorKind::NotImplemented(_) => "E999",
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}
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}
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@ -0,0 +1 @@
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[ [ ] [ 2 3 ] ]
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@ -0,0 +1,4 @@
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[
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(builtins.tail [ "foo" ])
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(builtins.tail [ 1 2 3 ])
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]
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