diff --git a/src/kv/error.rs b/src/kv/error.rs index 0439b3a55..c72d32396 100644 --- a/src/kv/error.rs +++ b/src/kv/error.rs @@ -11,6 +11,7 @@ enum Inner { #[cfg(feature = "std")] Boxed(std_support::BoxedError), Msg(&'static str), + Value(value_bag::Error), Fmt, } @@ -21,6 +22,24 @@ impl Error { inner: Inner::Msg(msg), } } + + // Not public so we don't leak the `value_bag` API + pub(super) fn from_value(err: value_bag::Error) -> Self { + Error { + inner: Inner::Value(err), + } + } + + // Not public so we don't leak the `value_bag` API + pub(super) fn into_value(self) -> value_bag::Error { + match self.inner { + Inner::Value(err) => err, + #[cfg(feature = "kv_unstable_std")] + _ => value_bag::Error::boxed(self), + #[cfg(not(feature = "kv_unstable_std"))] + _ => value_bag::Error::msg("error inspecting a value"), + } + } } impl fmt::Display for Error { @@ -29,6 +48,7 @@ impl fmt::Display for Error { match &self.inner { #[cfg(feature = "std")] &Boxed(ref err) => err.fmt(f), + &Value(ref err) => err.fmt(f), &Msg(ref msg) => msg.fmt(f), &Fmt => fmt::Error.fmt(f), } diff --git a/src/kv/value.rs b/src/kv/value.rs index 7dd108090..4cbbca583 100644 --- a/src/kv/value.rs +++ b/src/kv/value.rs @@ -263,6 +263,78 @@ impl<'v> Value<'v> { pub fn downcast_ref(&self) -> Option<&T> { self.inner.downcast_ref::() } + + /// Inspect this value using a simple visitor. + pub fn visit(&self, visitor: impl Visit<'v>) -> Result<(), Error> { + struct Visitor(V); + + impl<'v, V> value_bag::visit::Visit<'v> for Visitor + where + V: Visit<'v>, + { + fn visit_any(&mut self, value: ValueBag) -> Result<(), value_bag::Error> { + self.0 + .visit_any(Value { inner: value }) + .map_err(Error::into_value) + } + + fn visit_u64(&mut self, value: u64) -> Result<(), value_bag::Error> { + self.0.visit_u64(value).map_err(Error::into_value) + } + + fn visit_i64(&mut self, value: i64) -> Result<(), value_bag::Error> { + self.0.visit_i64(value).map_err(Error::into_value) + } + + fn visit_u128(&mut self, value: u128) -> Result<(), value_bag::Error> { + self.0.visit_u128(value).map_err(Error::into_value) + } + + fn visit_i128(&mut self, value: i128) -> Result<(), value_bag::Error> { + self.0.visit_i128(value).map_err(Error::into_value) + } + + fn visit_f64(&mut self, value: f64) -> Result<(), value_bag::Error> { + self.0.visit_f64(value).map_err(Error::into_value) + } + + fn visit_bool(&mut self, value: bool) -> Result<(), value_bag::Error> { + self.0.visit_bool(value).map_err(Error::into_value) + } + + fn visit_str(&mut self, value: &str) -> Result<(), value_bag::Error> { + self.0.visit_str(value).map_err(Error::into_value) + } + + fn visit_borrowed_str(&mut self, value: &'v str) -> Result<(), value_bag::Error> { + self.0.visit_borrowed_str(value).map_err(Error::into_value) + } + + fn visit_char(&mut self, value: char) -> Result<(), value_bag::Error> { + self.0.visit_char(value).map_err(Error::into_value) + } + + #[cfg(feature = "kv_unstable_std")] + fn visit_error( + &mut self, + err: &(dyn std::error::Error + 'static), + ) -> Result<(), value_bag::Error> { + self.0.visit_error(err).map_err(Error::into_value) + } + + #[cfg(feature = "kv_unstable_std")] + fn visit_borrowed_error( + &mut self, + err: &'v (dyn std::error::Error + 'static), + ) -> Result<(), value_bag::Error> { + self.0.visit_borrowed_error(err).map_err(Error::into_value) + } + } + + self.inner + .visit(&mut Visitor(visitor)) + .map_err(Error::from_value) + } } impl<'v> fmt::Debug for Value<'v> { @@ -448,6 +520,142 @@ mod std_support { self.inner.to_str() } } + + impl<'v> From<&'v String> for Value<'v> { + fn from(v: &'v String) -> Self { + Value::from(&**v) + } + } +} + +/// A visitor for a `Value`. +pub trait Visit<'v> { + /// Visit a `Value`. + /// + /// This is the only required method on `Visit` and acts as a fallback for any + /// more specific methods that aren't overridden. + /// The `Value` may be formatted using its `fmt::Debug` or `fmt::Display` implementation, + /// or serialized using its `sval::Value` or `serde::Serialize` implementation. + fn visit_any(&mut self, value: Value) -> Result<(), Error>; + + /// Visit an unsigned integer. + fn visit_u64(&mut self, value: u64) -> Result<(), Error> { + self.visit_any(value.into()) + } + + /// Visit a signed integer. + fn visit_i64(&mut self, value: i64) -> Result<(), Error> { + self.visit_any(value.into()) + } + + /// Visit a big unsigned integer. + fn visit_u128(&mut self, value: u128) -> Result<(), Error> { + self.visit_any(value.into()) + } + + /// Visit a big signed integer. + fn visit_i128(&mut self, value: i128) -> Result<(), Error> { + self.visit_any(value.into()) + } + + /// Visit a floating point. + fn visit_f64(&mut self, value: f64) -> Result<(), Error> { + self.visit_any(value.into()) + } + + /// Visit a boolean. + fn visit_bool(&mut self, value: bool) -> Result<(), Error> { + self.visit_any(value.into()) + } + + /// Visit a string. + fn visit_str(&mut self, value: &str) -> Result<(), Error> { + self.visit_any(value.into()) + } + + /// Visit a string. + fn visit_borrowed_str(&mut self, value: &'v str) -> Result<(), Error> { + self.visit_str(value) + } + + /// Visit a Unicode character. + fn visit_char(&mut self, value: char) -> Result<(), Error> { + let mut b = [0; 4]; + self.visit_str(&*value.encode_utf8(&mut b)) + } + + /// Visit an error. + #[cfg(feature = "kv_unstable_std")] + fn visit_error(&mut self, err: &(dyn std::error::Error + 'static)) -> Result<(), Error> { + self.visit_any(Value::from_dyn_error(err)) + } + + /// Visit an error. + #[cfg(feature = "kv_unstable_std")] + fn visit_borrowed_error( + &mut self, + err: &'v (dyn std::error::Error + 'static), + ) -> Result<(), Error> { + self.visit_any(Value::from_dyn_error(err)) + } +} + +impl<'a, 'v, T: ?Sized> Visit<'v> for &'a mut T +where + T: Visit<'v>, +{ + fn visit_any(&mut self, value: Value) -> Result<(), Error> { + (**self).visit_any(value) + } + + fn visit_u64(&mut self, value: u64) -> Result<(), Error> { + (**self).visit_u64(value) + } + + fn visit_i64(&mut self, value: i64) -> Result<(), Error> { + (**self).visit_i64(value) + } + + fn visit_u128(&mut self, value: u128) -> Result<(), Error> { + (**self).visit_u128(value) + } + + fn visit_i128(&mut self, value: i128) -> Result<(), Error> { + (**self).visit_i128(value) + } + + fn visit_f64(&mut self, value: f64) -> Result<(), Error> { + (**self).visit_f64(value) + } + + fn visit_bool(&mut self, value: bool) -> Result<(), Error> { + (**self).visit_bool(value) + } + + fn visit_str(&mut self, value: &str) -> Result<(), Error> { + (**self).visit_str(value) + } + + fn visit_borrowed_str(&mut self, value: &'v str) -> Result<(), Error> { + (**self).visit_borrowed_str(value) + } + + fn visit_char(&mut self, value: char) -> Result<(), Error> { + (**self).visit_char(value) + } + + #[cfg(feature = "kv_unstable_std")] + fn visit_error(&mut self, err: &(dyn std::error::Error + 'static)) -> Result<(), Error> { + (**self).visit_error(err) + } + + #[cfg(feature = "kv_unstable_std")] + fn visit_borrowed_error( + &mut self, + err: &'v (dyn std::error::Error + 'static), + ) -> Result<(), Error> { + (**self).visit_borrowed_error(err) + } } #[cfg(test)] @@ -652,4 +860,50 @@ pub(crate) mod tests { assert!(v.is::()); assert_eq!(42u64, v.downcast_ref::().expect("invalid downcast").0); } + + #[test] + fn test_visit_integer() { + struct Extract(Option); + + impl<'v> Visit<'v> for Extract { + fn visit_any(&mut self, value: Value) -> Result<(), Error> { + unimplemented!("unexpected value: {:?}", value) + } + + fn visit_u64(&mut self, value: u64) -> Result<(), Error> { + self.0 = Some(value); + + Ok(()) + } + } + + let mut extract = Extract(None); + Value::from(42u64).visit(&mut extract).unwrap(); + + assert_eq!(Some(42), extract.0); + } + + #[test] + fn test_visit_borrowed_str() { + struct Extract<'v>(Option<&'v str>); + + impl<'v> Visit<'v> for Extract<'v> { + fn visit_any(&mut self, value: Value) -> Result<(), Error> { + unimplemented!("unexpected value: {:?}", value) + } + + fn visit_borrowed_str(&mut self, value: &'v str) -> Result<(), Error> { + self.0 = Some(value); + + Ok(()) + } + } + + let mut extract = Extract(None); + + let short_lived = String::from("A short-lived string"); + Value::from(&*short_lived).visit(&mut extract).unwrap(); + + assert_eq!(Some("A short-lived string"), extract.0); + } }