juniper/value/scalar.rs
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use std::{borrow::Cow, fmt};
use serde::{de::DeserializeOwned, Serialize};
use crate::parser::{ParseError, ScalarToken};
pub use juniper_codegen::ScalarValue;
/// The result of converting a string into a scalar value
pub type ParseScalarResult<S = DefaultScalarValue> = Result<S, ParseError>;
/// A trait used to convert a `ScalarToken` into a certain scalar value type
pub trait ParseScalarValue<S = DefaultScalarValue> {
/// See the trait documentation
fn from_str(value: ScalarToken<'_>) -> ParseScalarResult<S>;
}
/// A trait marking a type that could be used as internal representation of
/// scalar values in juniper
///
/// The main objective of this abstraction is to allow other libraries to
/// replace the default representation with something that better fits their
/// needs.
/// There is a custom derive (`#[derive(`[`ScalarValue`]`)]`) available that
/// implements most of the required traits automatically for a enum representing
/// a scalar value. However, [`Serialize`] and [`Deserialize`] implementations
/// are expected to be provided.
///
/// # Implementing a new scalar value representation
/// The preferred way to define a new scalar value representation is
/// defining a enum containing a variant for each type that needs to be
/// represented at the lowest level.
/// The following example introduces an new variant that is able to store 64 bit
/// integers.
///
/// ```rust
/// # use std::fmt;
/// #
/// # use serde::{de, Deserialize, Deserializer, Serialize};
/// # use juniper::ScalarValue;
/// #
/// #[derive(Clone, Debug, PartialEq, ScalarValue, Serialize)]
/// #[serde(untagged)]
/// enum MyScalarValue {
/// #[value(as_float, as_int)]
/// Int(i32),
/// Long(i64),
/// #[value(as_float)]
/// Float(f64),
/// #[value(as_str, as_string, into_string)]
/// String(String),
/// #[value(as_bool)]
/// Boolean(bool),
/// }
///
/// impl<'de> Deserialize<'de> for MyScalarValue {
/// fn deserialize<D: Deserializer<'de>>(de: D) -> Result<Self, D::Error> {
/// struct Visitor;
///
/// impl<'de> de::Visitor<'de> for Visitor {
/// type Value = MyScalarValue;
///
/// fn expecting(&self, f: &mut fmt::Formatter) -> fmt::Result {
/// f.write_str("a valid input value")
/// }
///
/// fn visit_bool<E: de::Error>(self, b: bool) -> Result<Self::Value, E> {
/// Ok(MyScalarValue::Boolean(b))
/// }
///
/// fn visit_i32<E: de::Error>(self, n: i32) -> Result<Self::Value, E> {
/// Ok(MyScalarValue::Int(n))
/// }
///
/// fn visit_i64<E: de::Error>(self, n: i64) -> Result<Self::Value, E> {
/// if n <= i64::from(i32::MAX) {
/// self.visit_i32(n.try_into().unwrap())
/// } else {
/// Ok(MyScalarValue::Long(n))
/// }
/// }
///
/// fn visit_u32<E: de::Error>(self, n: u32) -> Result<Self::Value, E> {
/// if n <= i32::MAX as u32 {
/// self.visit_i32(n.try_into().unwrap())
/// } else {
/// self.visit_u64(n.into())
/// }
/// }
///
/// fn visit_u64<E: de::Error>(self, n: u64) -> Result<Self::Value, E> {
/// if n <= i64::MAX as u64 {
/// self.visit_i64(n.try_into().unwrap())
/// } else {
/// // Browser's `JSON.stringify()` serialize all numbers
/// // having no fractional part as integers (no decimal
/// // point), so we must parse large integers as floating
/// // point, otherwise we would error on transferring large
/// // floating point numbers.
/// Ok(MyScalarValue::Float(n as f64))
/// }
/// }
///
/// fn visit_f64<E: de::Error>(self, f: f64) -> Result<Self::Value, E> {
/// Ok(MyScalarValue::Float(f))
/// }
///
/// fn visit_str<E: de::Error>(self, s: &str) -> Result<Self::Value, E> {
/// self.visit_string(s.into())
/// }
///
/// fn visit_string<E: de::Error>(self, s: String) -> Result<Self::Value, E> {
/// Ok(MyScalarValue::String(s))
/// }
/// }
///
/// de.deserialize_any(Visitor)
/// }
/// }
/// ```
///
/// [`Deserialize`]: trait@serde::Deserialize
/// [`Serialize`]: trait@serde::Serialize
pub trait ScalarValue:
fmt::Debug
+ fmt::Display
+ PartialEq
+ Clone
+ DeserializeOwned
+ Serialize
+ From<String>
+ From<bool>
+ From<i32>
+ From<f64>
+ 'static
{
/// Checks whether this [`ScalarValue`] contains the value of the given
/// type.
///
/// ```
/// # use juniper::{ScalarValue, DefaultScalarValue};
/// #
/// let value = DefaultScalarValue::Int(42);
///
/// assert_eq!(value.is_type::<i32>(), true);
/// assert_eq!(value.is_type::<f64>(), false);
/// ```
#[must_use]
fn is_type<'a, T>(&'a self) -> bool
where
T: 'a,
Option<&'a T>: From<&'a Self>,
{
<Option<&'a T>>::from(self).is_some()
}
/// Represents this [`ScalarValue`] as an integer value.
///
/// This function is used for implementing [`GraphQLValue`] for [`i32`] for
/// all possible [`ScalarValue`]s. Implementations should convert all the
/// supported integer types with 32 bit or less to an integer, if requested.
///
/// [`GraphQLValue`]: crate::GraphQLValue
#[must_use]
fn as_int(&self) -> Option<i32>;
/// Represents this [`ScalarValue`] as a [`String`] value.
///
/// This function is used for implementing [`GraphQLValue`] for [`String`]
/// for all possible [`ScalarValue`]s.
///
/// [`GraphQLValue`]: crate::GraphQLValue
#[must_use]
fn as_string(&self) -> Option<String>;
/// Converts this [`ScalarValue`] into a [`String`] value.
///
/// Same as [`ScalarValue::as_string()`], but takes ownership, so allows to
/// omit redundant cloning.
#[must_use]
fn into_string(self) -> Option<String>;
/// Represents this [`ScalarValue`] as a [`str`] value.
///
/// This function is used for implementing [`GraphQLValue`] for [`str`] for
/// all possible [`ScalarValue`]s.
///
/// [`GraphQLValue`]: crate::GraphQLValue
#[must_use]
fn as_str(&self) -> Option<&str>;
/// Represents this [`ScalarValue`] as a float value.
///
/// This function is used for implementing [`GraphQLValue`] for [`f64`] for
/// all possible [`ScalarValue`]s. Implementations should convert all
/// supported integer types with 64 bit or less and all floating point
/// values with 64 bit or less to a float, if requested.
///
/// [`GraphQLValue`]: crate::GraphQLValue
#[must_use]
fn as_float(&self) -> Option<f64>;
/// Represents this [`ScalarValue`] as a boolean value
///
/// This function is used for implementing [`GraphQLValue`] for [`bool`] for
/// all possible [`ScalarValue`]s.
///
/// [`GraphQLValue`]: crate::GraphQLValue
fn as_bool(&self) -> Option<bool>;
/// Converts this [`ScalarValue`] into another one.
fn into_another<S: ScalarValue>(self) -> S {
if let Some(i) = self.as_int() {
S::from(i)
} else if let Some(f) = self.as_float() {
S::from(f)
} else if let Some(b) = self.as_bool() {
S::from(b)
} else if let Some(s) = self.into_string() {
S::from(s)
} else {
unreachable!("`ScalarValue` must represent at least one of the GraphQL spec types")
}
}
}
/// The default [`ScalarValue`] representation in [`juniper`].
///
/// These types closely follow the [GraphQL specification][0].
///
/// [0]: https://spec.graphql.org/October2021
#[derive(Clone, Debug, PartialEq, ScalarValue, Serialize)]
#[serde(untagged)]
pub enum DefaultScalarValue {
/// [`Int` scalar][0] as a signed 32‐bit numeric non‐fractional value.
///
/// [0]: https://spec.graphql.org/October2021#sec-Int
#[value(as_float, as_int)]
Int(i32),
/// [`Float` scalar][0] as a signed double‐precision fractional values as
/// specified by [IEEE 754].
///
/// [0]: https://spec.graphql.org/October2021#sec-Float
/// [IEEE 754]: https://en.wikipedia.org/wiki/IEEE_floating_point
#[value(as_float)]
Float(f64),
/// [`String` scalar][0] as a textual data, represented as UTF‐8 character
/// sequences.
///
/// [0]: https://spec.graphql.org/October2021#sec-String
#[value(as_str, as_string, into_string)]
String(String),
/// [`Boolean` scalar][0] as a `true` or `false` value.
///
/// [0]: https://spec.graphql.org/October2021#sec-Boolean
#[value(as_bool)]
Boolean(bool),
}
impl<'a> From<&'a str> for DefaultScalarValue {
fn from(s: &'a str) -> Self {
Self::String(s.into())
}
}
impl<'a> From<Cow<'a, str>> for DefaultScalarValue {
fn from(s: Cow<'a, str>) -> Self {
Self::String(s.into())
}
}