Merge pull request #189 from Nadrieril/serialize

3 files changed, 275 insertions, 28 deletions

diff --git a/serde_dhall/src/options.rs b/serde_dhall/src/options/de.rs
index 7b27114..e4f3456 100644
--- a/serde_dhall/src/options.rs
+++ b/serde_dhall/src/options/de.rs
@@ -2,8 +2,9 @@ use std::path::{Path, PathBuf};
 
 use dhall::Parsed;
 
+use crate::options::{HasAnnot, ManualAnnot, NoAnnot, StaticAnnot, TypeAnnot};
 use crate::SimpleType;
-use crate::{Error, ErrorKind, FromDhall, Result, StaticType, Value};
+use crate::{Error, ErrorKind, FromDhall, Result, Value};
 
 #[derive(Debug, Clone)]
 enum Source<'a> {
@@ -12,32 +13,6 @@ enum Source<'a> {
     // Url(&'a str),
 }
 
-#[derive(Debug, Clone, Copy)]
-pub struct NoAnnot;
-#[derive(Debug, Clone, Copy)]
-pub struct ManualAnnot<'ty>(&'ty SimpleType);
-#[derive(Debug, Clone, Copy)]
-pub struct StaticAnnot;
-
-pub trait HasAnnot<A> {
-    fn get_annot(a: &A) -> Option<SimpleType>;
-}
-impl<T> HasAnnot<NoAnnot> for T {
-    fn get_annot(_: &NoAnnot) -> Option<SimpleType> {
-        None
-    }
-}
-impl<'ty, T> HasAnnot<ManualAnnot<'ty>> for T {
-    fn get_annot(a: &ManualAnnot<'ty>) -> Option<SimpleType> {
-        Some(a.0.clone())
-    }
-}
-impl<T: StaticType> HasAnnot<StaticAnnot> for T {
-    fn get_annot(_: &StaticAnnot) -> Option<SimpleType> {
-        Some(T::static_type())
-    }
-}
-
 /// Controls how a Dhall value is read.
 ///
 /// This builder exposes the ability to configure how a value is deserialized and what operations
@@ -252,6 +227,7 @@ impl<'a, A> Deserializer<'a, A> {
 
     fn _parse<T>(&self) -> dhall::error::Result<Value>
     where
+        A: TypeAnnot,
         T: HasAnnot<A>,
     {
         let parsed = match &self.source {
@@ -263,7 +239,7 @@ impl<'a, A> Deserializer<'a, A> {
         } else {
             parsed.skip_resolve()?
         };
-        let typed = match &T::get_annot(&self.annot) {
+        let typed = match &T::get_annot(self.annot) {
             None => resolved.typecheck()?,
             Some(ty) => resolved.typecheck_with(ty.to_value().as_hir())?,
         };
@@ -287,6 +263,7 @@ impl<'a, A> Deserializer<'a, A> {
     /// [`StaticType`]: trait.StaticType.html
     pub fn parse<T>(&self) -> Result<T>
     where
+        A: TypeAnnot,
         T: FromDhall + HasAnnot<A>,
     {
         let val = self
diff --git a/serde_dhall/src/options/mod.rs b/serde_dhall/src/options/mod.rs
new file mode 100644
index 0000000..9241c45
--- /dev/null
+++ b/serde_dhall/src/options/mod.rs
@@ -0,0 +1,36 @@
+use crate::{SimpleType, StaticType};
+
+pub(crate) mod de;
+pub(crate) mod ser;
+
+#[derive(Debug, Clone, Copy)]
+pub struct NoAnnot;
+#[derive(Debug, Clone, Copy)]
+pub struct ManualAnnot<'ty>(&'ty SimpleType);
+#[derive(Debug, Clone, Copy)]
+pub struct StaticAnnot;
+
+pub trait TypeAnnot: Copy {}
+pub trait HasAnnot<A: TypeAnnot> {
+    fn get_annot(a: A) -> Option<SimpleType>;
+}
+
+impl TypeAnnot for NoAnnot {}
+impl TypeAnnot for ManualAnnot<'_> {}
+impl TypeAnnot for StaticAnnot {}
+
+impl<T> HasAnnot<NoAnnot> for T {
+    fn get_annot(_: NoAnnot) -> Option<SimpleType> {
+        None
+    }
+}
+impl<T> HasAnnot<ManualAnnot<'_>> for T {
+    fn get_annot(a: ManualAnnot<'_>) -> Option<SimpleType> {
+        Some(a.0.clone())
+    }
+}
+impl<T: StaticType> HasAnnot<StaticAnnot> for T {
+    fn get_annot(_: StaticAnnot) -> Option<SimpleType> {
+        Some(T::static_type())
+    }
+}
diff --git a/serde_dhall/src/options/ser.rs b/serde_dhall/src/options/ser.rs
new file mode 100644
index 0000000..d74beb0
--- /dev/null
+++ b/serde_dhall/src/options/ser.rs
@@ -0,0 +1,234 @@
+use crate::options::{HasAnnot, ManualAnnot, NoAnnot, StaticAnnot, TypeAnnot};
+use crate::{Result, SimpleType, ToDhall};
+
+/// Controls how a Dhall value is written.
+///
+/// This builder exposes the ability to configure how a value is serialized, and to set type
+/// annotations.
+///
+/// When using [`Serializer`], you'll create it with [`serialize`], then chain calls to methods to
+/// set each option, then call [`to_string`]. This will give you a [`Result<String>`] containing
+/// the input serialized to Dhall.
+///
+/// Note that if you do not provide a type annotation, some values may not be convertible to Dhall,
+/// like empty lists or enums.
+///
+/// [`Serializer`]: struct.Serializer.html
+/// [`serialize`]: fn.serialize.html
+/// [`to_string`]: struct.Serializer.html#method.to_string
+/// [`Result<String>`]: type.Result.html
+///
+/// # Examples
+///
+/// Serializing without a type annotation:
+///
+/// ```rust
+/// # fn main() -> serde_dhall::Result<()> {
+/// use serde_dhall::serialize;
+///
+/// let string = serialize(&1i64).to_string()?;
+/// assert_eq!(string, "+1".to_string());
+/// # Ok(())
+/// # }
+/// ```
+///
+/// Serializing with an automatic type annotation:
+///
+/// ```rust
+/// # fn main() -> serde_dhall::Result<()> {
+/// use serde_dhall::serialize;
+///
+/// let data: Option<u64> = None;
+/// let string = serialize(&data).static_type_annotation().to_string()?;
+/// assert_eq!(string, "None Natural".to_string());
+/// # Ok(())
+/// # }
+/// ```
+#[derive(Debug, Clone)]
+pub struct Serializer<'a, T, A> {
+    data: &'a T,
+    annot: A,
+}
+
+impl<'a, T> Serializer<'a, T, NoAnnot> {
+    /// Provides a type to the serialization process. The provided value will be checked against
+    /// that type, and the type will be used when Dhall needs it, like for empty lists or for
+    /// unions.
+    ///
+    /// In many cases the Dhall type that corresponds to a Rust type can be inferred automatically.
+    /// See the [`StaticType`] trait and the [`static_type_annotation`] method for that.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # fn main() -> serde_dhall::Result<()> {
+    /// use serde_dhall::{serialize, from_str, SimpleType, SimpleValue};
+    ///
+    /// let ty = from_str("< A | B: Bool >").parse()?;
+    /// let data = SimpleValue::Union("A".to_string(), None);
+    /// let string = serialize(&data)
+    ///     .type_annotation(&ty)
+    ///     .to_string()?;
+    /// assert_eq!(string, "< A | B: Bool >.A".to_string());
+    ///
+    /// // Invalid data fails the type validation; serialization would have succeeded otherwise.
+    /// let ty = SimpleType::Integer;
+    /// assert!(
+    ///     serialize(&Some(0u64))
+    ///         .type_annotation(&ty)
+    ///         .to_string()
+    ///         .is_err()
+    /// );
+    /// # Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`static_type_annotation`]: struct.Serializer.html#method.static_type_annotation
+    /// [`StaticType`]: trait.StaticType.html
+    pub fn type_annotation<'ty>(
+        self,
+        ty: &'ty SimpleType,
+    ) -> Serializer<'a, T, ManualAnnot<'ty>> {
+        Serializer {
+            annot: ManualAnnot(ty),
+            data: self.data,
+        }
+    }
+
+    /// Uses the type of `T` in the serialization process. This will be used when Dhall needs it,
+    /// like for empty lists or for unions.
+    ///
+    /// `T` must implement the [`StaticType`] trait. If it doesn't, you can use [`type_annotation`]
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # fn main() -> serde_dhall::Result<()> {
+    /// use serde::Serialize;
+    /// use serde_dhall::{serialize, StaticType};
+    ///
+    /// #[derive(Serialize, StaticType)]
+    /// enum MyOption {
+    ///     MyNone,
+    ///     MySome(u64),
+    /// }
+    ///
+    /// let data = MyOption::MySome(0);
+    /// let string = serialize(&data)
+    ///     .static_type_annotation()
+    ///     .to_string()?;
+    /// // The resulting Dhall string depends on the type annotation; it could not have been
+    /// // printed without it.
+    /// assert_eq!(string, "< MyNone | MySome: Natural >.MySome 0".to_string());
+    /// # Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`type_annotation`]: struct.Serializer.html#method.type_annotation
+    /// [`StaticType`]: trait.StaticType.html
+    pub fn static_type_annotation(self) -> Serializer<'a, T, StaticAnnot> {
+        Serializer {
+            annot: StaticAnnot,
+            data: self.data,
+        }
+    }
+}
+
+impl<'a, T, A> Serializer<'a, T, A>
+where
+    A: TypeAnnot,
+{
+    /// Prints the chosen value with the options provided.
+    ///
+    /// If you enabled static annotations, `T` is required to implement [`StaticType`].
+    ///
+    /// Note that if you do not provide a type annotation, some values may not be convertible to
+    /// Dhall, like empty lists or enums.
+    ///
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// # fn main() -> serde_dhall::Result<()> {
+    /// use serde_dhall::serialize;
+    ///
+    /// let string = serialize(&1i64).static_type_annotation().to_string()?;
+    /// assert_eq!(string, "+1".to_string());
+    /// # Ok(())
+    /// # }
+    /// ```
+    ///
+    /// [`StaticType`]: trait.StaticType.html
+    pub fn to_string(&self) -> Result<String>
+    where
+        T: ToDhall + HasAnnot<A>,
+    {
+        let val = self.data.to_dhall(T::get_annot(self.annot).as_ref())?;
+        Ok(val.to_string())
+    }
+}
+
+/// Serialize a value to a string of Dhall text.
+///
+/// This returns a [`Serializer`] object. Call the [`to_string`] method to get the serialized
+/// value, or use other [`Serializer`] methods to control the serialization process.
+///
+/// In order to process certain values (like unions or empty lists) correctly, it is necessary to
+/// add a type annotation (with [`static_type_annotation`] or [`type_annotation`]).
+///
+/// # Examples
+///
+/// ```rust
+/// # fn main() -> serde_dhall::Result<()> {
+/// use serde::Serialize;
+/// use serde_dhall::{serialize, StaticType};
+///
+/// #[derive(Serialize)]
+/// struct Point {
+///     x: u64,
+///     y: u64,
+/// }
+///
+///
+/// let data = Point { x: 0, y: 0 };
+/// let string = serialize(&data).to_string()?;
+/// assert_eq!(string, "{ x = 0, y = 0 }");
+/// # Ok(())
+/// # }
+/// ```
+///
+/// ```rust
+/// # fn main() -> serde_dhall::Result<()> {
+/// use serde::Serialize;
+/// use serde_dhall::{serialize, StaticType};
+///
+/// #[derive(Serialize, StaticType)]
+/// enum MyOption {
+///     MyNone,
+///     MySome(u64),
+/// }
+///
+/// let data = MyOption::MySome(0);
+/// let string = serialize(&data)
+///     .static_type_annotation()
+///     .to_string()?;
+/// // The resulting Dhall string depends on the type annotation; it could not have been
+/// // printed without it.
+/// assert_eq!(string, "< MyNone | MySome: Natural >.MySome 0".to_string());
+/// # Ok(())
+/// # }
+/// ```
+///
+/// [`Serializer`]: struct.Serializer.html
+/// [`type_annotation`]: struct.Serializer.html#method.type_annotation
+/// [`static_type_annotation`]: struct.Serializer.html#method.static_type_annotation
+/// [`to_string`]: struct.Serializer.html#method.to_string
+pub fn serialize<T>(data: &T) -> Serializer<'_, T, NoAnnot>
+where
+    T: ToDhall,
+{
+    Serializer {
+        data,
+        annot: NoAnnot,
+    }
+}