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//! Type level fields for fun and profit. use super::{reply::Reply, Response}; use frunk_core::hlist::{HCons, HNil}; use serde::{ de::{self, DeserializeOwned}, ser, Deserialize, Serialize, }; use std::{ fmt, marker::PhantomData, ops::{Deref, DerefMut}, str::FromStr, }; /// Access a [named field][Field] in an hlist. /// /// # First form: evaluates to a statement that moves an hlist field into a variable /// Immutable: `zoom!(new_variable = my_record.field_name)` /// /// Mutable: `zoom!(mut new_variable = my_record.field_name)` /// /// The result will be a *statement* that extracts a field, binds its value to the specified /// identifier, and shadows the original hlist with any remaining fields. /// /// The new hlist will be declared as `mut` in all cases. /// /// ``` /// use hyperbole::{r, zoom, R}; /// /// let rec = r![x = 1000, y = "hello world"]; /// /// zoom!(s = rec.y); /// assert_eq!(s, "hello world"); /// /// // NOTE: 'rec' is now eqivalent to 'let mut rec = r![x = 1000]' /// /// zoom!(n = rec.x); /// assert_eq!(n, 1000); /// /// // NOTE: 'rec' is now empty and contains no fields /// let _: R![] = rec; /// ``` /// /// # Second form: evaluates to an expression that borrows a field /// For immutable borrows: `zoom!(&my_record.field_name)` /// /// For mutable borrows: `zoom!(&mut my_record.field_name)` /// /// ``` /// use hyperbole::{r, zoom, R}; /// /// let mut rec = r![x = 1000, y = "hello world"]; /// /// let _: &u64 = zoom!(&rec.x); /// let _: &mut u64 = zoom!(&mut rec.x); /// /// assert_eq!(1000, *zoom!(&rec.x)); /// assert_eq!("hello world", *zoom!(&rec.y)); /// /// *zoom!(&mut rec.y) = "changed"; /// assert_eq!("changed", *zoom!(&rec.y)); /// /// // the type and mutability of 'rec' has not changed /// let _: R![x: u64, y: &str] = rec; /// ``` #[macro_export] macro_rules! zoom { ($var:ident = $rec:ident . $field:ident) => { #[allow(unused_mut)] let (val, mut $rec) = $rec.pluck::<$crate::f![$field], _>(); let $var = val.into_inner(); }; (mut $var:ident = $rec:ident . $field:ident) => { #[allow(unused_mut)] let (val, mut $rec) = $rec.pluck::<$crate::f![$field], _>(); let mut $var = val.into_inner(); }; (&$rec:ident . $field:ident) => { &**($rec.get::<$crate::f![$field], _>()) }; (&mut $rec:ident . $field:ident) => { &mut **($rec.get_mut::<$crate::f![$field], _>()) }; } /// Expands to the type of an hlist that may contain named fields. /// /// [Named fields][Field] are used to disambiguate elements of the same type, as most logic in this /// crate depends on types being unique within hlists. /// /// Any invocation may contain an arbitrary number of comma separated elements of the form `Type` /// or `name: Type`. Optionally, `...Type` may be added to the end in order to append the elements /// of another hlist. /// /// The [r!] macro may be used to instantiate an hlist value. /// /// # Examples /// ``` /// use frunk_core::hlist::{HCons, HNil}; /// use hyperbole::{f, R}; /// # /// # macro_rules! assert_type_eq { /// # ($t1:ty, $t2:ty) => {{ /// # fn check(mut t1: $t1, t2: $t2) { /// # t1 = t2; /// # } /// # }}; /// # } /// /// type T = R![u16, u32, u64]; /// type _T = HCons<u16, HCons<u32, HCons<u64, HNil>>>; /// assert_type_eq!(T, _T); /// /// type U = R![x: u16, y: u32, z: u64]; /// type _U = HCons<f![x: u16], HCons<f![y: u32], HCons<f![z: u64], HNil>>>; /// assert_type_eq!(U, _U); /// /// type V = R![u16, x: u32, u64]; /// type _V = HCons<u16, HCons<f![x: u32], HCons<u64, HNil>>>; /// assert_type_eq!(V, _V); /// /// type W = R![foo: String, ...T]; /// type _W = HCons<f![foo: String], HCons<u16, HCons<u32, HCons<u64, HNil>>>>; /// assert_type_eq!(W, _W); /// ``` #[macro_export] macro_rules! R { () => { $crate::frunk_core::hlist::HNil }; ($name:ident : $type:ty) => { $crate::frunk_core::hlist::HCons< $crate::field::Field::<$type, { stringify!($name) }>, $crate::frunk_core::hlist::HNil, > }; ($name:ident : $type:ty , $( $tok:tt )*) => { $crate::frunk_core::hlist::HCons< $crate::field::Field::<$type, { stringify!($name) }>, $crate::R![$( $tok )*], > }; ($type:ty) => { $crate::frunk_core::hlist::HCons<$type, $crate::frunk_core::hlist::HNil> }; ($type:ty , $( $tok:tt )*) => { $crate::frunk_core::hlist::HCons<$type, $crate::R![$( $tok )*]> }; (... $tail:ty) => { $tail } } /// Expands to an hlist that may contain named fields. /// /// [Named fields][Field] are used to disambiguate elements of the same type, as most logic in this /// crate depends on types being unique within hlists. /// /// Any invocation may contain an arbitrary number of comma separated elements of the form `expr` /// or `name = expr`. Optionally, `...expr` may be added to the end in order to append the elements /// of another hlist. /// /// The [R!] macro may be used to name the type of the produced hlist. /// /// # Examples /// As hlists are effectively singly linked lists at the type level, the simplest way to refer to /// an individual element is to follow the struct fields directly: /// /// ``` /// use hyperbole::r; /// /// let rec = r![1, 2, 3]; /// /// assert_eq!(rec.head, 1); /// assert_eq!(rec.tail.head, 2); /// assert_eq!(rec.tail.tail.head, 3); /// ``` /// /// Alternatively, they can be converted into tuples: /// /// ``` /// use hyperbole::r; /// /// let rec = r![1, "foo", "bar".to_owned()]; /// let (a, b, c) = rec.into(); /// /// assert_eq!(a, 1); /// assert_eq!(b, "foo"); /// assert_eq!(c, "bar"); /// ``` /// /// See [HCons][frunk_core::hlist::HCons] for more advanced usage. #[macro_export] macro_rules! r { () => { $crate::frunk_core::hlist::HNil }; (... $tail:expr) => { $tail }; ($name:ident = $value:expr) => { $crate::frunk_core::hlist::HCons { head: $crate::field::Field::<_, { stringify!($name) }>::new($value), tail: $crate::frunk_core::hlist::HNil, } }; ($name:ident = $value:expr , $( $tok:tt )*) => { $crate::frunk_core::hlist::HCons { head: $crate::field::Field::<_, { stringify!($name) }>::new($value), tail: $crate::r![$( $tok )*], } }; ($value:expr) => { $crate::frunk_core::hlist::HCons { head: $value, tail: $crate::frunk_core::hlist::HNil, } }; ($value:expr , $( $tok:tt )*) => { $crate::frunk_core::hlist::HCons { head: $value, tail: $crate::r![$( $tok )*], } }; } /// Expands to either the type of a [named field][Field], or a (~consty) expression that evaluates /// to an instantiated field. /// /// # First form: evaluates to the type of a named field with an inferred value type /// /// ``` /// use hyperbole::f; /// /// let one: f![abc] = 256.into(); /// let two: f![abc] = one; /// ``` /// /// Named fields with different names have different types, so for example this will not compile: /// /// ```compile_fail,E0308 /// use hyperbole::f; /// /// let one: f![abc] = 1234.into(); /// let two: f![bca] = one; /// ``` /// /// # Second form: evaluates to the type of a named field with a concrete value type /// /// ``` /// use hyperbole::f; /// /// let one: f![abc: u32] = 40.into(); /// let two: f![bca: &str] = "hello world".into(); /// ``` /// /// # Third form: evaluates to an instantiated named field /// /// ``` /// use hyperbole::f; /// /// let one = f![hello_world = "this string"]; /// /// const TWO: f![xyz: &str] = f![xyz = "is const"]; /// ``` #[macro_export] macro_rules! f { ($name:ident) => { $crate::field::Field<_, { stringify!($name) }> }; ($name:ident : $type:ty) => { $crate::field::Field<$type, { stringify!($name) }> }; ($name:ident = $val:expr) => { $crate::field::Field::<_, { stringify!($name) }>::new($val) }; } /// A named value where the name is lifted to the type level, analagous to a struct field. /// /// This struct is intended to be named and instantiated via the [f!] or [r!] / [R!] macros. /// /// For convenience, `Field<T>` implements [Deref] and [DerefMut] for `T`, as well as a number of /// fundamental traits like [Clone], [Debug], etc. Consider it a smart pointer to a `T`. /// /// # Examples /// ``` /// use hyperbole::f; /// /// let mut field = f![foo = "neat".to_owned()]; /// /// assert_eq!(4, field.len()); // Deref<Target = String> /// field.push('o'); // DerefMut /// assert_eq!("neato", format!("{}", field)); // Display /// assert_eq!(field, field.clone()); // Clone /// /// assert_eq!("foo", field.name()); /// ``` #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)] pub struct Field<T, const NAME: &'static str> { inner: T, } impl<T, const NAME: &'static str> Field<T, NAME> { /// Returns a new field. #[inline] pub const fn new(inner: T) -> Self { Self { inner } } /// Extracts the field's inner value. #[inline] pub fn into_inner(self) -> T { self.inner } /// The field's name. pub const NAME: &'static str = NAME; /// The field's name. pub const fn name(&self) -> &'static str { Self::NAME } } impl<T, const NAME: &'static str> From<T> for Field<T, NAME> { #[inline] fn from(inner: T) -> Self { Self::new(inner) } } impl<T, const NAME: &'static str> Deref for Field<T, NAME> { type Target = T; #[inline] fn deref(&self) -> &Self::Target { &self.inner } } impl<T, const NAME: &'static str> DerefMut for Field<T, NAME> { #[inline] fn deref_mut(&mut self) -> &mut Self::Target { &mut self.inner } } impl<T: FromStr, const NAME: &'static str> FromStr for Field<T, NAME> { type Err = T::Err; #[inline] fn from_str(input: &str) -> Result<Self, Self::Err> { Ok(Self::new(input.parse()?)) } } impl<T: fmt::Debug, const NAME: &'static str> fmt::Debug for Field<T, NAME> { #[inline] fn fmt(&self, w: &mut fmt::Formatter<'_>) -> fmt::Result { write!(w, "{} = {:?}", NAME, self.inner) } } impl<T: fmt::Display, const NAME: &'static str> fmt::Display for Field<T, NAME> { #[inline] fn fmt(&self, w: &mut fmt::Formatter<'_>) -> fmt::Result { self.inner.fmt(w) } } impl<T: Reply, const NAME: &'static str> Reply for Field<T, NAME> { #[inline] fn into_response(self) -> Response { self.inner.into_response() } } impl<T: Serialize, const NAME: &'static str> Serialize for Field<T, NAME> { fn serialize<S: ser::Serializer>(&self, s: S) -> Result<S::Ok, S::Error> { use ser::SerializeStruct; let mut s = s.serialize_struct("Field", 1)?; s.serialize_field(Self::NAME, &self.inner)?; s.end() } } trait Named { const NAME: &'static str; } impl<T, const NAME: &'static str> Named for Field<T, NAME> { const NAME: &'static str = NAME; } impl<'de, T: Deserialize<'de>, const NAME: &'static str> Deserialize<'de> for Field<T, NAME> { fn deserialize<D: de::Deserializer<'de>>(d: D) -> Result<Self, D::Error> { enum Tag<Up> { Good(PhantomData<fn(Up)>), Ignore(PhantomData<fn(Up)>), } struct TagVisitor<Up>(PhantomData<fn(Up)>); impl<'de, Up: Named> de::Visitor<'de> for TagVisitor<Up> { type Value = Tag<Up>; #[inline] fn expecting(&self, w: &mut fmt::Formatter<'_>) -> fmt::Result { write!(w, "field identifier") } #[inline] fn visit_u64<E: de::Error>(self, val: u64) -> Result<Self::Value, E> { if val == 0 { return Ok(Tag::Good(PhantomData)); } Err(de::Error::invalid_value( de::Unexpected::Unsigned(val), &"field index 0 <= i < 1", )) } #[inline] fn visit_str<E: de::Error>(self, val: &str) -> Result<Self::Value, E> { if val == Up::NAME { Ok(Tag::Good(PhantomData)) } else { Ok(Tag::Ignore(PhantomData)) } } #[inline] fn visit_bytes<E: de::Error>(self, val: &[u8]) -> Result<Self::Value, E> { if val == Up::NAME.as_bytes() { Ok(Tag::Good(PhantomData)) } else { Ok(Tag::Ignore(PhantomData)) } } } impl<'de, Up: Named> Deserialize<'de> for Tag<Up> { #[inline] fn deserialize<D: de::Deserializer<'de>>(d: D) -> Result<Self, D::Error> { d.deserialize_identifier(TagVisitor::<Up>(PhantomData)) } } struct Visitor<T, const NAME: &'static str>(PhantomData<fn(Field<T, NAME>)>); impl<'de, T: Deserialize<'de>, const NAME: &'static str> de::Visitor<'de> for Visitor<T, NAME> { type Value = Field<T, NAME>; #[inline] fn expecting(&self, w: &mut fmt::Formatter<'_>) -> fmt::Result { write!(w, "struct Field") } #[inline] fn visit_seq<A: de::SeqAccess<'de>>(self, mut seq: A) -> Result<Self::Value, A::Error> { let inner = seq .next_element::<T>()? .ok_or_else(|| de::Error::invalid_length(0, &"struct Field with 1 element"))?; Ok(Field { inner }) } #[inline] fn visit_map<A: de::MapAccess<'de>>(self, mut map: A) -> Result<Self::Value, A::Error> { let mut inner: Option<T> = None; while let Some(tag) = map.next_key::<Tag<Self::Value>>()? { match tag { Tag::Good(_) if inner.is_some() => { return Err(de::Error::duplicate_field(NAME)) } Tag::Good(_) => { inner = Some(map.next_value()?); } Tag::Ignore(_) => { map.next_value::<de::IgnoredAny>()?; } } } let inner = inner.ok_or_else(|| de::Error::missing_field(NAME))?; Ok(Field { inner }) } } d.deserialize_struct("Field", &[NAME], Visitor::<T, NAME>(PhantomData)) } } #[derive(Copy, Clone, Default, Serialize, Deserialize)] #[serde(default)] #[doc(hidden)] pub struct RNil { #[serde(skip)] __: (), } #[derive(Copy, Clone, Serialize, Deserialize)] #[doc(hidden)] pub struct RCons<T, Tail> { #[serde(flatten)] head: T, #[serde(flatten)] tail: Tail, } /// Types with an alternate representation that is [Serialize]. /// /// For hlists, the serialization format is equivalent to a struct with the same fields: /// /// ``` /// use hyperbole::{field::IsoEncode, r}; /// use serde::Serialize; /// /// #[derive(Serialize)] /// struct MyRequest { /// a: String, /// b: u32, /// c: f32, /// } /// /// let my_req = serde_json::to_string(&MyRequest { /// a: "hello-worldo".into(), /// b: 32324, /// c: 345345.34, /// }) /// .unwrap(); /// /// let my_req_r = serde_json::to_string( /// &r! { /// a = "hello-worldo".to_string(), /// b = 32324, /// c = 345345.34, /// } /// .as_repr(), /// ) /// .unwrap(); /// /// // both of the above serialize to: /// let repr = r#"{"a":"hello-worldo","b":32324,"c":345345.34}"#; /// /// assert_eq!(repr, my_req); /// assert_eq!(repr, my_req_r); /// ``` pub trait IsoEncode<'a> { /// The representation. type Repr: Serialize; /// Convert to the representation. fn as_repr(&'a self) -> Self::Repr; } impl<'a> IsoEncode<'a> for HNil { type Repr = RNil; #[inline] fn as_repr(&'a self) -> Self::Repr { RNil { __: () } } } impl<'a, T: Serialize + 'a, Tail: IsoEncode<'a>> IsoEncode<'a> for HCons<T, Tail> { type Repr = RCons<&'a T, Tail::Repr>; #[inline] fn as_repr(&'a self) -> Self::Repr { RCons { head: &self.head, tail: self.tail.as_repr(), } } } /// Types with an alternate representation that is [DeserializeOwned]. /// /// For hlists, the deserialization format is equivalent to a struct with the same fields: /// /// ``` /// use hyperbole::{field::IsoDecode, zoom, R}; /// use serde::Deserialize; /// /// #[derive(Deserialize)] /// struct MyRequest { /// a: String, /// b: u32, /// c: f32, /// } /// /// let repr = r#"{"a":"hello-worldo","b":32324,"c":345345.34}"#; /// /// let my_req: MyRequest = serde_json::from_str(repr).unwrap(); /// /// let my_req_r: R![a: String, b: u32, c: f32] = serde_json::from_str(repr) /// .map(IsoDecode::from_repr) /// .unwrap(); /// /// assert_eq!(my_req.a, *zoom![&my_req_r.a]); /// assert_eq!(my_req.b, *zoom![&my_req_r.b]); /// assert_eq!(my_req.c, *zoom![&my_req_r.c]); /// ``` pub trait IsoDecode { /// The representation. type Repr: DeserializeOwned; /// Convert from the representation. fn from_repr(repr: Self::Repr) -> Self; } impl IsoDecode for HNil { type Repr = RNil; #[inline] fn from_repr(_: Self::Repr) -> Self { HNil } } impl<T: DeserializeOwned, Tail: IsoDecode> IsoDecode for HCons<T, Tail> { type Repr = RCons<T, Tail::Repr>; #[inline] fn from_repr(repr: Self::Repr) -> Self { HCons { head: repr.head, tail: Tail::from_repr(repr.tail), } } } #[cfg(test)] mod tests { use super::*; use quickcheck_macros::quickcheck; fn iso_de<T: IsoDecode>(input: &str) -> T { T::from_repr(serde_json::from_str(input).unwrap()) } fn iso_ser<'a, T: IsoEncode<'a>>(input: &'a T) -> String { serde_json::to_string(&input.as_repr()).unwrap() } fn ser_de_ser<T: IsoDecode + PartialEq + fmt::Debug>(input: T) where T: for<'a> IsoEncode<'a> { let encoded = iso_ser(&input); let decoded: T = iso_de(&encoded); assert_eq!(input, decoded); } fn de_ser_de<T: IsoDecode>(input: &str) where T: for<'a> IsoEncode<'a> { let decoded: T = iso_de(input); let encoded = iso_ser(&decoded); assert_eq!(input, encoded); } #[quickcheck] fn serde_iso_roundtrips(x: u32, y: String, z: f32) { ser_de_ser(r![x = x, y = y.clone()]); ser_de_ser(r![y = y, x = x, z = z]); de_ser_de::<R![x: u32, y: String, z: f32]>(r#"{"x":32,"y":"neat","z":4.4}"#); } }