Move api-related modules into an api module

6 files changed, 347 insertions, 0 deletions

diff --git a/dhall/src/api/mod.rs b/dhall/src/api/mod.rs
new file mode 100644
index 0000000..1522c9c
--- /dev/null
+++ b/dhall/src/api/mod.rs
@@ -0,0 +1,38 @@
+mod serde;
+pub(crate) mod traits;
+
+/// Deserialization of Dhall expressions into Rust
+pub mod de {
+    pub use crate::traits::{Deserialize, SimpleStaticType, StaticType};
+    #[doc(hidden)]
+    pub use dhall_proc_macros::SimpleStaticType;
+
+    /// Deserialize an instance of type T from a string of Dhall text.
+    ///
+    /// This will recursively resolve all imports in the expression, and
+    /// typecheck it before deserialization. Relative imports will be resolved relative to the
+    /// provided file. More control over this process is not yet available
+    /// but will be in a coming version of this crate.
+    ///
+    /// If a type is provided, this additionally checks that the provided
+    /// expression has that type.
+    pub fn from_str<'a, T: Deserialize<'a>>(
+        s: &'a str,
+        ty: Option<&crate::phase::Type>,
+    ) -> crate::error::Result<T> {
+        T::from_str(s, ty)
+    }
+
+    /// Deserialize an instance of type T from a string of Dhall text,
+    /// additionally checking that it matches the type of T.
+    ///
+    /// This will recursively resolve all imports in the expression, and
+    /// typecheck it before deserialization. Relative imports will be resolved relative to the
+    /// provided file. More control over this process is not yet available
+    /// but will be in a coming version of this crate.
+    pub fn from_str_auto_type<'a, T: Deserialize<'a> + StaticType>(
+        s: &'a str,
+    ) -> crate::error::Result<T> {
+        from_str(s, Some(&<T as StaticType>::get_static_type()))
+    }
+}
diff --git a/dhall/src/api/serde.rs b/dhall/src/api/serde.rs
new file mode 100644
index 0000000..93921ba
--- /dev/null
+++ b/dhall/src/api/serde.rs
@@ -0,0 +1,69 @@
+use crate::error::{Error, Result};
+use crate::phase::{Normalized, Type};
+use crate::traits::Deserialize;
+use dhall_syntax::*;
+use std::borrow::Cow;
+
+impl<'a, T: serde::Deserialize<'a>> Deserialize<'a> for T {
+    fn from_str(s: &'a str, ty: Option<&Type>) -> Result<Self> {
+        let expr = Normalized::from_str(s, ty)?;
+        T::deserialize(Deserializer(Cow::Owned(expr.to_expr())))
+    }
+}
+
+struct Deserializer<'a>(Cow<'a, SubExpr<X, X>>);
+
+impl serde::de::Error for Error {
+    fn custom<T>(msg: T) -> Self
+    where
+        T: std::fmt::Display,
+    {
+        Error::Deserialize(msg.to_string())
+    }
+}
+
+impl<'de: 'a, 'a> serde::de::IntoDeserializer<'de, Error> for Deserializer<'a> {
+    type Deserializer = Deserializer<'a>;
+    fn into_deserializer(self) -> Self::Deserializer {
+        self
+    }
+}
+
+impl<'de: 'a, 'a> serde::Deserializer<'de> for Deserializer<'a> {
+    type Error = Error;
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: serde::de::Visitor<'de>,
+    {
+        use std::convert::TryInto;
+        use ExprF::*;
+        match self.0.as_ref().as_ref() {
+            NaturalLit(n) => match (*n).try_into() {
+                Ok(n64) => visitor.visit_u64(n64),
+                Err(_) => match (*n).try_into() {
+                    Ok(n32) => visitor.visit_u32(n32),
+                    Err(_) => unimplemented!(),
+                },
+            },
+            IntegerLit(n) => match (*n).try_into() {
+                Ok(n64) => visitor.visit_i64(n64),
+                Err(_) => match (*n).try_into() {
+                    Ok(n32) => visitor.visit_i32(n32),
+                    Err(_) => unimplemented!(),
+                },
+            },
+            RecordLit(m) => visitor.visit_map(
+                serde::de::value::MapDeserializer::new(m.iter().map(
+                    |(k, v)| (k.as_ref(), Deserializer(Cow::Borrowed(v))),
+                )),
+            ),
+            _ => unimplemented!(),
+        }
+    }
+
+    serde::forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct enum identifier ignored_any
+    }
+}
diff --git a/dhall/src/api/traits/deserialize.rs b/dhall/src/api/traits/deserialize.rs
new file mode 100644
index 0000000..9673cf9
--- /dev/null
+++ b/dhall/src/api/traits/deserialize.rs
@@ -0,0 +1,53 @@
+use crate::error::*;
+use crate::phase::*;
+
+/// A data structure that can be deserialized from a Dhall expression
+///
+/// This is automatically implemented for any type that [serde][serde]
+/// can deserialize.
+///
+/// This trait cannot be implemented manually.
+pub trait Deserialize<'de>: Sized {
+    /// See [dhall::de::from_str][crate::de::from_str]
+    fn from_str(s: &'de str, ty: Option<&Type>) -> Result<Self>;
+}
+
+impl<'de> Deserialize<'de> for Parsed {
+    /// Simply parses the provided string. Ignores the
+    /// provided type.
+    fn from_str(s: &'de str, _: Option<&Type>) -> Result<Self> {
+        Ok(Parsed::parse_str(s)?)
+    }
+}
+
+impl<'de> Deserialize<'de> for Resolved {
+    /// Parses and resolves the provided string. Ignores the
+    /// provided type.
+    fn from_str(s: &'de str, ty: Option<&Type>) -> Result<Self> {
+        Ok(Parsed::from_str(s, ty)?.resolve()?)
+    }
+}
+
+impl<'de> Deserialize<'de> for Typed {
+    /// Parses, resolves and typechecks the provided string.
+    fn from_str(s: &'de str, ty: Option<&Type>) -> Result<Self> {
+        let resolved = Resolved::from_str(s, ty)?;
+        match ty {
+            None => Ok(resolved.typecheck()?),
+            Some(t) => Ok(resolved.typecheck_with(t)?),
+        }
+    }
+}
+
+impl<'de> Deserialize<'de> for Normalized {
+    /// Parses, resolves, typechecks and normalizes the provided string.
+    fn from_str(s: &'de str, ty: Option<&Type>) -> Result<Self> {
+        Ok(Typed::from_str(s, ty)?.normalize())
+    }
+}
+
+impl<'de> Deserialize<'de> for Type {
+    fn from_str(s: &'de str, ty: Option<&Type>) -> Result<Self> {
+        Ok(Normalized::from_str(s, ty)?.to_type())
+    }
+}
diff --git a/dhall/src/api/traits/dynamic_type.rs b/dhall/src/api/traits/dynamic_type.rs
new file mode 100644
index 0000000..7763a28
--- /dev/null
+++ b/dhall/src/api/traits/dynamic_type.rs
@@ -0,0 +1,32 @@
+use crate::error::TypeError;
+use crate::phase::{Normalized, Type, Typed};
+use crate::traits::StaticType;
+use std::borrow::Cow;
+
+pub trait DynamicType {
+    fn get_type<'a>(&'a self) -> Result<Cow<'a, Type>, TypeError>;
+}
+
+impl<T: StaticType> DynamicType for T {
+    fn get_type<'a>(&'a self) -> Result<Cow<'a, Type>, TypeError> {
+        Ok(Cow::Owned(T::get_static_type()))
+    }
+}
+
+impl DynamicType for Type {
+    fn get_type(&self) -> Result<Cow<'_, Type>, TypeError> {
+        self.get_type()
+    }
+}
+
+impl DynamicType for Normalized {
+    fn get_type(&self) -> Result<Cow<'_, Type>, TypeError> {
+        self.0.get_type()
+    }
+}
+
+impl DynamicType for Typed {
+    fn get_type(&self) -> Result<Cow<'_, Type>, TypeError> {
+        self.get_type()
+    }
+}
diff --git a/dhall/src/api/traits/mod.rs b/dhall/src/api/traits/mod.rs
new file mode 100644
index 0000000..315e17a
--- /dev/null
+++ b/dhall/src/api/traits/mod.rs
@@ -0,0 +1,6 @@
+mod deserialize;
+mod dynamic_type;
+mod static_type;
+pub use deserialize::Deserialize;
+pub use dynamic_type::DynamicType;
+pub use static_type::{SimpleStaticType, StaticType};
diff --git a/dhall/src/api/traits/static_type.rs b/dhall/src/api/traits/static_type.rs
new file mode 100644
index 0000000..8b141a0
--- /dev/null
+++ b/dhall/src/api/traits/static_type.rs
@@ -0,0 +1,149 @@
+use crate::phase::*;
+use dhall_proc_macros as dhall;
+use dhall_syntax::*;
+
+/// A value that has a statically-known Dhall type.
+///
+/// This trait is strictly more general than [SimpleStaticType].
+/// The reason is that it allows an arbitrary [Type] to be returned
+/// instead of just a [SimpleType].
+///
+/// For now the only interesting impl is [SimpleType] itself, who
+/// has a statically-known type which is not itself a [SimpleType].
+pub trait StaticType {
+    fn get_static_type() -> Type;
+}
+
+/// A Rust type that can be represented as a Dhall type.
+///
+/// A typical example is `Option<bool>`,
+/// represented by the dhall expression `Optional Bool`.
+///
+/// This trait can and should be automatically derived.
+///
+/// The representation needs to be independent of the value.
+/// For this reason, something like `HashMap<String, bool>` cannot implement
+/// [SimpleStaticType] because each different value would
+/// have a different Dhall record type.
+///
+/// The `Simple` in `SimpleStaticType` indicates that the returned type is
+/// a [SimpleType].
+pub trait SimpleStaticType {
+    fn get_simple_static_type() -> SimpleType;
+}
+
+fn mktype(x: SubExpr<X, X>) -> SimpleType {
+    x.into()
+}
+
+impl<T: SimpleStaticType> StaticType for T {
+    fn get_static_type() -> Type {
+        crate::phase::Normalized::from_thunk_and_type(
+            crate::phase::normalize::Thunk::from_normalized_expr(
+                T::get_simple_static_type().into(),
+            ),
+            Type::const_type(),
+        )
+        .to_type()
+    }
+}
+
+impl StaticType for SimpleType {
+    /// By definition, a [SimpleType] has type `Type`.
+    /// This returns the Dhall expression `Type`
+    fn get_static_type() -> Type {
+        Type::const_type()
+    }
+}
+
+impl SimpleStaticType for bool {
+    fn get_simple_static_type() -> SimpleType {
+        mktype(dhall::subexpr!(Bool))
+    }
+}
+
+impl SimpleStaticType for Natural {
+    fn get_simple_static_type() -> SimpleType {
+        mktype(dhall::subexpr!(Natural))
+    }
+}
+
+impl SimpleStaticType for u32 {
+    fn get_simple_static_type() -> SimpleType {
+        mktype(dhall::subexpr!(Natural))
+    }
+}
+
+impl SimpleStaticType for u64 {
+    fn get_simple_static_type() -> SimpleType {
+        mktype(dhall::subexpr!(Natural))
+    }
+}
+
+impl SimpleStaticType for Integer {
+    fn get_simple_static_type() -> SimpleType {
+        mktype(dhall::subexpr!(Integer))
+    }
+}
+
+impl SimpleStaticType for i32 {
+    fn get_simple_static_type() -> SimpleType {
+        mktype(dhall::subexpr!(Integer))
+    }
+}
+
+impl SimpleStaticType for i64 {
+    fn get_simple_static_type() -> SimpleType {
+        mktype(dhall::subexpr!(Integer))
+    }
+}
+
+impl SimpleStaticType for String {
+    fn get_simple_static_type() -> SimpleType {
+        mktype(dhall::subexpr!(Text))
+    }
+}
+
+impl<A: SimpleStaticType, B: SimpleStaticType> SimpleStaticType for (A, B) {
+    fn get_simple_static_type() -> SimpleType {
+        let ta: SubExpr<_, _> = A::get_simple_static_type().into();
+        let tb: SubExpr<_, _> = B::get_simple_static_type().into();
+        mktype(dhall::subexpr!({ _1: ta, _2: tb }))
+    }
+}
+
+impl<T: SimpleStaticType> SimpleStaticType for Option<T> {
+    fn get_simple_static_type() -> SimpleType {
+        let t: SubExpr<_, _> = T::get_simple_static_type().into();
+        mktype(dhall::subexpr!(Optional t))
+    }
+}
+
+impl<T: SimpleStaticType> SimpleStaticType for Vec<T> {
+    fn get_simple_static_type() -> SimpleType {
+        let t: SubExpr<_, _> = T::get_simple_static_type().into();
+        mktype(dhall::subexpr!(List t))
+    }
+}
+
+impl<'a, T: SimpleStaticType> SimpleStaticType for &'a T {
+    fn get_simple_static_type() -> SimpleType {
+        T::get_simple_static_type()
+    }
+}
+
+impl<T> SimpleStaticType for std::marker::PhantomData<T> {
+    fn get_simple_static_type() -> SimpleType {
+        mktype(dhall::subexpr!({}))
+    }
+}
+
+impl<T: SimpleStaticType, E: SimpleStaticType> SimpleStaticType
+    for std::result::Result<T, E>
+{
+    fn get_simple_static_type() -> SimpleType {
+        let tt: SubExpr<_, _> = T::get_simple_static_type().into();
+        let te: SubExpr<_, _> = E::get_simple_static_type().into();
+        mktype(dhall::subexpr!(< Ok: tt | Err: te>))
+    }
+}