diff options
author | Nadrieril | 2020-04-05 17:57:07 +0100 |
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committer | GitHub | 2020-04-05 17:57:07 +0100 |
commit | 7e977f282fb6a0eff0ef45738b9b5c98dc4c6fee (patch) | |
tree | ad4249609707fd8720a44469152105c2f6a67c79 /serde_dhall/src/value.rs | |
parent | 5a5aa49e64197899006751db72e404f4b2292d4e (diff) | |
parent | 820214615547101f8f2b5de209b5189968bddfee (diff) |
Merge pull request #154 from Nadrieril/cleanup-api
Rewrite serde_dhall API
Diffstat (limited to 'serde_dhall/src/value.rs')
-rw-r--r-- | serde_dhall/src/value.rs | 287 |
1 files changed, 287 insertions, 0 deletions
diff --git a/serde_dhall/src/value.rs b/serde_dhall/src/value.rs new file mode 100644 index 0000000..d6631da --- /dev/null +++ b/serde_dhall/src/value.rs @@ -0,0 +1,287 @@ +use std::collections::{BTreeMap, HashMap}; + +use dhall::semantics::{Hir, HirKind, Nir, NirKind}; +use dhall::syntax::{Builtin, Expr, ExprKind, NumKind, Span}; + +use crate::{Error, ErrorKind, FromDhall, Result, Sealed}; + +#[doc(hidden)] +/// An arbitrary Dhall value. +#[derive(Debug, Clone)] +pub struct Value { + /// Invariant: in normal form + hir: Hir, + /// Cached conversions because they are annoying to construct from Hir. + /// At most one of them will be `Some`. + as_simple_val: Option<SimpleValue>, + as_simple_ty: Option<SimpleType>, +} + +/// A simple value of the kind that can be decoded with serde +#[derive(Debug, Clone, PartialEq, Eq)] +pub(crate) enum SimpleValue { + Num(NumKind), + Text(String), + Optional(Option<Box<SimpleValue>>), + List(Vec<SimpleValue>), + Record(BTreeMap<String, SimpleValue>), + Union(String, Option<Box<SimpleValue>>), +} + +/// The type of a value that can be decoded by `serde_dhall`, e.g. `{ x: Bool, y: List Natural }`. +/// +/// A `SimpleType` is used when deserializing values to ensure they are of the expected type. +/// Rather than letting `serde` handle potential type mismatches, this uses the type-checking +/// capabilities of Dhall to catch errors early and cleanly indicate in the user's code where the +/// mismatch happened. +/// +/// You would typically not manipulate `SimpleType`s by hand but rather let Rust infer it for your +/// datatype by deriving the [`StaticType`] trait, and using +/// [`Deserializer::static_type_annotation`]. If you need to supply a `SimpleType` manually, you +/// can either deserialize it like any other Dhall value, or construct it manually. +/// +/// [`StaticType`]: trait.StaticType.html +/// [`Deserializer::static_type_annotation`]: options/struct.Deserializer.html#method.static_type_annotation +/// +/// # Examples +/// +/// ```rust +/// # fn main() -> serde_dhall::Result<()> { +/// use serde_dhall::{SimpleType, StaticType}; +/// +/// #[derive(StaticType)] +/// struct Foo { +/// x: bool, +/// y: Vec<u64>, +/// } +/// +/// let ty: SimpleType = +/// serde_dhall::from_str("{ x: Bool, y: List Natural }").parse()?; +/// +/// assert_eq!(Foo::static_type(), ty); +/// # Ok(()) +/// # } +/// ``` +/// +/// ```rust +/// # fn main() -> serde_dhall::Result<()> { +/// use std::collections::HashMap; +/// use serde_dhall::SimpleType; +/// +/// let ty: SimpleType = +/// serde_dhall::from_str("{ x: Natural, y: Natural }").parse()?; +/// +/// let mut map = HashMap::new(); +/// map.insert("x".to_string(), SimpleType::Natural); +/// map.insert("y".to_string(), SimpleType::Natural); +/// assert_eq!(ty, SimpleType::Record(map)); +/// # Ok(()) +/// # } +/// ``` +/// +#[derive(Debug, Clone, PartialEq, Eq)] +pub enum SimpleType { + /// Corresponds to the Dhall type `Bool` + Bool, + /// Corresponds to the Dhall type `Natural` + Natural, + /// Corresponds to the Dhall type `Integer` + Integer, + /// Corresponds to the Dhall type `Double` + Double, + /// Corresponds to the Dhall type `Text` + Text, + /// Corresponds to the Dhall type `Optional T` + Optional(Box<SimpleType>), + /// Corresponds to the Dhall type `List T` + List(Box<SimpleType>), + /// Corresponds to the Dhall type `{ x : T, y : U }` + Record(HashMap<String, SimpleType>), + /// Corresponds to the Dhall type `< x : T | y : U >` + Union(HashMap<String, Option<SimpleType>>), +} + +impl Value { + pub(crate) fn from_nir(x: &Nir) -> Self { + Value { + hir: x.to_hir_noenv(), + as_simple_val: SimpleValue::from_nir(x), + as_simple_ty: SimpleType::from_nir(x), + } + } + + pub(crate) fn as_hir(&self) -> &Hir { + &self.hir + } + + /// Converts a Value into a SimpleValue. + pub(crate) fn to_simple_value(&self) -> Option<SimpleValue> { + self.as_simple_val.clone() + } + + /// Converts a Value into a SimpleType. + pub(crate) fn to_simple_type(&self) -> Option<SimpleType> { + self.as_simple_ty.clone() + } + + /// Converts a value back to the corresponding AST expression. + pub(crate) fn to_expr(&self) -> Expr { + self.hir.to_expr(Default::default()) + } +} + +impl SimpleValue { + pub(crate) fn from_nir(nir: &Nir) -> Option<Self> { + Some(match nir.kind() { + NirKind::Num(lit) => SimpleValue::Num(lit.clone()), + NirKind::TextLit(x) => SimpleValue::Text( + x.as_text() + .expect("Normal form should ensure the text is a string"), + ), + NirKind::EmptyOptionalLit(_) => SimpleValue::Optional(None), + NirKind::NEOptionalLit(x) => { + SimpleValue::Optional(Some(Box::new(Self::from_nir(x)?))) + } + NirKind::EmptyListLit(_) => SimpleValue::List(vec![]), + NirKind::NEListLit(xs) => SimpleValue::List( + xs.iter().map(Self::from_nir).collect::<Option<_>>()?, + ), + NirKind::RecordLit(kvs) => SimpleValue::Record( + kvs.iter() + .map(|(k, v)| Some((k.into(), Self::from_nir(v)?))) + .collect::<Option<_>>()?, + ), + NirKind::UnionLit(field, x, _) => SimpleValue::Union( + field.into(), + Some(Box::new(Self::from_nir(x)?)), + ), + NirKind::UnionConstructor(field, ty) + if ty.get(field).map(|f| f.is_some()) == Some(false) => + { + SimpleValue::Union(field.into(), None) + } + _ => return None, + }) + } +} + +impl SimpleType { + pub(crate) fn from_nir(nir: &Nir) -> Option<Self> { + Some(match nir.kind() { + NirKind::BuiltinType(b) => match b { + Builtin::Bool => SimpleType::Bool, + Builtin::Natural => SimpleType::Natural, + Builtin::Integer => SimpleType::Integer, + Builtin::Double => SimpleType::Double, + Builtin::Text => SimpleType::Text, + _ => unreachable!(), + }, + NirKind::OptionalType(t) => { + SimpleType::Optional(Box::new(Self::from_nir(t)?)) + } + NirKind::ListType(t) => { + SimpleType::List(Box::new(Self::from_nir(t)?)) + } + NirKind::RecordType(kts) => SimpleType::Record( + kts.iter() + .map(|(k, v)| Some((k.into(), Self::from_nir(v)?))) + .collect::<Option<_>>()?, + ), + NirKind::UnionType(kts) => SimpleType::Union( + kts.iter() + .map(|(k, v)| { + Some(( + k.into(), + v.as_ref() + .map(|v| Ok(Self::from_nir(v)?)) + .transpose()?, + )) + }) + .collect::<Option<_>>()?, + ), + _ => return None, + }) + } + + pub(crate) fn to_value(&self) -> Value { + Value { + hir: self.to_hir(), + as_simple_val: None, + as_simple_ty: Some(self.clone()), + } + } + pub(crate) fn to_hir(&self) -> Hir { + let hir = |k| Hir::new(HirKind::Expr(k), Span::Artificial); + hir(match self { + SimpleType::Bool => ExprKind::Builtin(Builtin::Bool), + SimpleType::Natural => ExprKind::Builtin(Builtin::Natural), + SimpleType::Integer => ExprKind::Builtin(Builtin::Integer), + SimpleType::Double => ExprKind::Builtin(Builtin::Double), + SimpleType::Text => ExprKind::Builtin(Builtin::Text), + SimpleType::Optional(t) => ExprKind::App( + hir(ExprKind::Builtin(Builtin::Optional)), + t.to_hir(), + ), + SimpleType::List(t) => { + ExprKind::App(hir(ExprKind::Builtin(Builtin::List)), t.to_hir()) + } + SimpleType::Record(kts) => ExprKind::RecordType( + kts.iter() + .map(|(k, t)| (k.as_str().into(), t.to_hir())) + .collect(), + ), + SimpleType::Union(kts) => ExprKind::UnionType( + kts.iter() + .map(|(k, t)| { + (k.as_str().into(), t.as_ref().map(|t| t.to_hir())) + }) + .collect(), + ), + }) + } +} + +impl Sealed for Value {} +impl Sealed for SimpleValue {} +impl Sealed for SimpleType {} + +impl FromDhall for Value { + fn from_dhall(v: &Value) -> Result<Self> { + Ok(v.clone()) + } +} +impl FromDhall for SimpleValue { + fn from_dhall(v: &Value) -> Result<Self> { + v.to_simple_value().ok_or_else(|| { + Error(ErrorKind::Deserialize(format!( + "this cannot be deserialized into a simple type: {}", + v + ))) + }) + } +} +impl FromDhall for SimpleType { + fn from_dhall(v: &Value) -> Result<Self> { + v.to_simple_type().ok_or_else(|| { + Error(ErrorKind::Deserialize(format!( + "this cannot be deserialized into a simple type: {}", + v + ))) + }) + } +} + +impl Eq for Value {} +impl PartialEq for Value { + fn eq(&self, other: &Self) -> bool { + self.hir == other.hir + } +} +impl std::fmt::Display for Value { + fn fmt( + &self, + f: &mut std::fmt::Formatter, + ) -> std::result::Result<(), std::fmt::Error> { + self.to_expr().fmt(f) + } +} |