From 34be6466d4a5da7dd3ad55ce80c951f21e45520c Mon Sep 17 00:00:00 2001 From: Vincent Ambo Date: Mon, 2 Jan 2023 13:39:42 +0300 Subject: feat(tvix/serde): implement enum deserialisation Implements externally tagged enum deserialisation. Other serialisation methods are handled by serde internally using the existing methods. See the tests for examples. Change-Id: Ic4a9da3b5a32ddbb5918b1512e70c3ac5ce64f04 Reviewed-on: https://cl.tvl.fyi/c/depot/+/7721 Tested-by: BuildkiteCI Autosubmit: tazjin Reviewed-by: flokli --- tvix/serde/src/de.rs | 81 ++++++++++++++++++++++++++++++++--- tvix/serde/src/de_tests.rs | 103 +++++++++++++++++++++++++++++++++++++++++++++ tvix/serde/src/error.rs | 10 +++++ 3 files changed, 188 insertions(+), 6 deletions(-) (limited to 'tvix/serde') diff --git a/tvix/serde/src/de.rs b/tvix/serde/src/de.rs index 2f7b2ba4d6..e6bcf41cf2 100644 --- a/tvix/serde/src/de.rs +++ b/tvix/serde/src/de.rs @@ -1,7 +1,7 @@ //! Deserialisation from Nix to Rust values. -use serde::de; use serde::de::value::{MapDeserializer, SeqDeserializer}; +use serde::de::{self, EnumAccess, VariantAccess}; use tvix_eval::Value; use crate::error::Error; @@ -221,14 +221,14 @@ impl<'de> de::Deserializer<'de> for NixDeserializer { Err(unexpected("string", &self.value)) } - fn deserialize_bytes(self, visitor: V) -> Result + fn deserialize_bytes(self, _visitor: V) -> Result where V: de::Visitor<'de>, { unimplemented!() } - fn deserialize_byte_buf(self, visitor: V) -> Result + fn deserialize_byte_buf(self, _visitor: V) -> Result where V: de::Visitor<'de>, { @@ -307,7 +307,7 @@ impl<'de> de::Deserializer<'de> for NixDeserializer { fn deserialize_tuple_struct( self, _name: &'static str, - len: usize, + _len: usize, visitor: V, ) -> Result where @@ -348,16 +348,27 @@ impl<'de> de::Deserializer<'de> for NixDeserializer { self.deserialize_map(visitor) } + // This method is responsible for deserializing the externally + // tagged enum variant serialisation. fn deserialize_enum( self, name: &'static str, - variants: &'static [&'static str], + _variants: &'static [&'static str], visitor: V, ) -> Result where V: de::Visitor<'de>, { - todo!() + match self.value { + // a string represents a unit variant + Value::String(s) => visitor.visit_enum(de::value::StrDeserializer::new(s.as_str())), + + // an attribute set however represents an externally + // tagged enum with content + Value::Attrs(attrs) => visitor.visit_enum(Enum(*attrs)), + + _ => Err(unexpected(name, &self.value)), + } } fn deserialize_identifier(self, visitor: V) -> Result @@ -374,3 +385,61 @@ impl<'de> de::Deserializer<'de> for NixDeserializer { visitor.visit_unit() } } + +struct Enum(tvix_eval::NixAttrs); + +impl<'de> EnumAccess<'de> for Enum { + type Error = Error; + type Variant = NixDeserializer; + + // TODO: pass the known variants down here and check against them + fn variant_seed(self, seed: V) -> Result<(V::Value, Self::Variant), Self::Error> + where + V: de::DeserializeSeed<'de>, + { + if self.0.len() != 1 { + return Err(Error::AmbiguousEnum); + } + + let (key, value) = self.0.into_iter().next().expect("length asserted above"); + let val = seed.deserialize(de::value::StrDeserializer::::new(key.as_str()))?; + + Ok((val, NixDeserializer::new(value))) + } +} + +impl<'de> VariantAccess<'de> for NixDeserializer { + type Error = Error; + + fn unit_variant(self) -> Result<(), Self::Error> { + // If this case is hit, a user specified the name of a unit + // enum variant but gave it content. Unit enum deserialisation + // is handled in `deserialize_enum` above. + Err(Error::UnitEnumContent) + } + + fn newtype_variant_seed(self, seed: T) -> Result + where + T: de::DeserializeSeed<'de>, + { + seed.deserialize(self) + } + + fn tuple_variant(self, _len: usize, visitor: V) -> Result + where + V: de::Visitor<'de>, + { + de::Deserializer::deserialize_seq(self, visitor) + } + + fn struct_variant( + self, + _fields: &'static [&'static str], + visitor: V, + ) -> Result + where + V: de::Visitor<'de>, + { + de::Deserializer::deserialize_map(self, visitor) + } +} diff --git a/tvix/serde/src/de_tests.rs b/tvix/serde/src/de_tests.rs index 1613b874d9..8fe15a17e3 100644 --- a/tvix/serde/src/de_tests.rs +++ b/tvix/serde/src/de_tests.rs @@ -95,3 +95,106 @@ fn deserialize_tuple() { let result: (String, usize) = from_str(r#" [ "foo" 42 ] "#).expect("should deserialize"); assert_eq!(result, ("foo".into(), 42)); } + +#[test] +fn deserialize_unit_enum() { + #[derive(Debug, Deserialize, PartialEq)] + enum Foo { + Bar, + Baz, + } + + let result: Foo = from_str("\"Baz\"").expect("should deserialize"); + assert_eq!(result, Foo::Baz); +} + +#[test] +fn deserialize_tuple_enum() { + #[derive(Debug, Deserialize, PartialEq)] + enum Foo { + Bar, + Baz(String, usize), + } + + let result: Foo = from_str( + r#" + { + Baz = [ "Slartibartfast" 42 ]; + } + "#, + ) + .expect("should deserialize"); + + assert_eq!(result, Foo::Baz("Slartibartfast".into(), 42)); +} + +#[test] +fn deserialize_struct_enum() { + #[derive(Debug, Deserialize, PartialEq)] + enum Foo { + Bar, + Baz { name: String, age: usize }, + } + + let result: Foo = from_str( + r#" + { + Baz.name = "Slartibartfast"; + Baz.age = 42; + } + "#, + ) + .expect("should deserialize"); + + assert_eq!( + result, + Foo::Baz { + name: "Slartibartfast".into(), + age: 42 + } + ); +} + +#[test] +fn deserialize_enum_all() { + #[derive(Debug, Deserialize, PartialEq)] + #[serde(rename_all = "snake_case")] + enum TestEnum { + UnitVariant, + TupleVariant(String, String), + StructVariant { name: String, age: usize }, + } + + let result: Vec = from_str( + r#" + let + mkTuple = country: drink: { tuple_variant = [ country drink ]; }; + in + [ + (mkTuple "UK" "cask ale") + + "unit_variant" + + { + struct_variant.name = "Slartibartfast"; + struct_variant.age = 42; + } + + (mkTuple "Russia" "квас") + ] + "#, + ) + .expect("should deserialize"); + + let expected = vec![ + TestEnum::TupleVariant("UK".into(), "cask ale".into()), + TestEnum::UnitVariant, + TestEnum::StructVariant { + name: "Slartibartfast".into(), + age: 42, + }, + TestEnum::TupleVariant("Russia".into(), "квас".into()), + ]; + + assert_eq!(result, expected); +} diff --git a/tvix/serde/src/error.rs b/tvix/serde/src/error.rs index fb83105cd2..f206b830e9 100644 --- a/tvix/serde/src/error.rs +++ b/tvix/serde/src/error.rs @@ -31,6 +31,12 @@ pub enum Error { errors: Vec, source: tvix_eval::SourceCode, }, + + /// Could not determine an externally tagged enum representation. + AmbiguousEnum, + + /// Attempted to provide content to a unit enum. + UnitEnumContent, } impl Display for Error { @@ -69,6 +75,10 @@ impl Display for Error { Error::IntegerConversion { got, need } => { write!(f, "i64({}) does not fit in a {}", got, need) } + + Error::AmbiguousEnum => write!(f, "could not determine enum variant: ambiguous keys"), + + Error::UnitEnumContent => write!(f, "provided content for unit enum variant"), } } } -- cgit 1.4.1