Rework #[derive(GraphQLInputObject)] macro implementation (#1052)

Co-authored-by: Kai Ren <tyranron@gmail.com>

juniper/src/executor_tests/introspection/input_object.rs

@@ -76,9 +76,9 @@ struct FieldDescription {
 
 #[derive(GraphQLInputObject, Debug)]
 struct FieldWithDefaults {
-    #[graphql(default = "123")]
+    #[graphql(default = 123)]
     field_one: i32,
-    #[graphql(default = "456", description = "The second field")]
+    #[graphql(default = 456, description = "The second field")]
     field_two: i32,
 }
 

juniper/src/executor_tests/variables.rs

@@ -49,7 +49,7 @@ struct ExampleInputObject {
 
 #[derive(GraphQLInputObject, Debug)]
 struct InputWithDefaults {
-    #[graphql(default = "123")]
+    #[graphql(default = 123)]
     a: i32,
 }
 

juniper_codegen/src/common/default.rs

@@ -0,0 +1,65 @@
+//! Common functions, definitions and extensions for parsing and code generation
+//! of [GraphQL default values][0]
+//!
+//! [0]: https://spec.graphql.org/October2021#DefaultValue
+
+use proc_macro2::TokenStream;
+use quote::{quote, ToTokens};
+use syn::{
+    parse::{Parse, ParseStream},
+    token,
+};
+
+use crate::common::parse::ParseBufferExt as _;
+
+/// Representation of a [GraphQL default value][0] for code generation.
+///
+/// [0]: https://spec.graphql.org/October2021#DefaultValue
+#[derive(Clone, Debug)]
+pub(crate) enum Value {
+    /// [`Default`] implementation should be used.
+    Default,
+
+    /// Explicit [`Expr`]ession to be used as the [default value][0].
+    ///
+    /// [`Expr`]: syn::Expr
+    /// [0]: https://spec.graphql.org/October2021#DefaultValue
+    Expr(Box<syn::Expr>),
+}
+
+impl Default for Value {
+    fn default() -> Self {
+        Self::Default
+    }
+}
+
+impl From<Option<syn::Expr>> for Value {
+    fn from(opt: Option<syn::Expr>) -> Self {
+        match opt {
+            Some(expr) => Self::Expr(Box::new(expr)),
+            None => Self::Default,
+        }
+    }
+}
+
+impl Parse for Value {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        Ok(input
+            .try_parse::<token::Eq>()?
+            .map(|_| input.parse::<syn::Expr>())
+            .transpose()?
+            .into())
+    }
+}
+
+impl ToTokens for Value {
+    fn to_tokens(&self, into: &mut TokenStream) {
+        match self {
+            Self::Default => quote! {
+                ::std::default::Default::default()
+            }
+            .to_tokens(into),
+            Self::Expr(expr) => expr.to_tokens(into),
+        }
+    }
+}

juniper_codegen/src/common/field/mod.rs

@@ -1,7 +1,7 @@
 //! Common functions, definitions and extensions for parsing and code generation
 //! of [GraphQL fields][1]
 //!
-//! [1]: https://spec.graphql.org/June2018/#sec-Language.Fields.
+//! [1]: https://spec.graphql.org/June2018/#sec-Language.Fields
 
 pub(crate) mod arg;
 
@@ -42,16 +42,16 @@ pub(crate) struct Attr {
 
     /// Explicitly specified [description][2] of this [GraphQL field][1].
     ///
-    /// If [`None`], then Rust doc comment is used as the [description][2], if
-    /// any.
+    /// If [`None`], then Rust doc comment will be used as the [description][2],
+    /// if any.
     ///
     /// [1]: https://spec.graphql.org/June2018/#sec-Language.Fields
     /// [2]: https://spec.graphql.org/June2018/#sec-Descriptions
     pub(crate) description: Option<SpanContainer<syn::LitStr>>,
 
     /// Explicitly specified [deprecation][2] of this [GraphQL field][1].
     ///
-    /// If [`None`], then Rust `#[deprecated]` attribute is used as the
+    /// If [`None`], then Rust `#[deprecated]` attribute will be used as the
     /// [deprecation][2], if any.
     ///
     /// [1]: https://spec.graphql.org/June2018/#sec-Language.Fields

juniper_codegen/src/common/mod.rs

@@ -1,5 +1,6 @@
 //! Common functions, definitions and extensions for code generation, used by this crate.
 
+pub(crate) mod default;
 pub(crate) mod field;
 pub(crate) mod gen;
 pub(crate) mod parse;

juniper_codegen/src/graphql_enum/derive.rs

@@ -1,8 +1,9 @@
 //! Code generation for `#[derive(GraphQLEnum)]` macro.
 
+use std::collections::HashSet;
+
 use proc_macro2::TokenStream;
 use quote::ToTokens as _;
-use std::collections::HashSet;
 use syn::{ext::IdentExt as _, parse_quote, spanned::Spanned};
 
 use crate::{

juniper_codegen/src/graphql_enum/mod.rs

@@ -30,7 +30,7 @@ use crate::{
 };
 
 /// Available arguments behind `#[graphql]` attribute placed on a Rust enum
-/// definition, when generating code for a [GraphQL enum][0] type.
+/// definition, when generating code for a [GraphQL enum][0].
 ///
 /// [0]: https://spec.graphql.org/October2021#sec-Enums
 #[derive(Debug, Default)]
@@ -44,8 +44,8 @@ struct ContainerAttr {
 
     /// Explicitly specified [description][2] of this [GraphQL enum][0].
     ///
-    /// If [`None`], then Rust doc comment will be used as [description][2], if
-    /// any.
+    /// If [`None`], then Rust doc comment will be used as the [description][2],
+    /// if any.
     ///
     /// [0]: https://spec.graphql.org/October2021#sec-Enums
     /// [2]: https://spec.graphql.org/October2021#sec-Descriptions
@@ -190,22 +190,23 @@ impl ContainerAttr {
 struct VariantAttr {
     /// Explicitly specified name of this [GraphQL enum value][1].
     ///
-    /// If [`None`], then Rust enum variant's name is used by default.
+    /// If [`None`], then Rust enum variant's name will be used by default.
     ///
     /// [1]: https://spec.graphql.org/October2021#sec-Enum-Value
     name: Option<SpanContainer<String>>,
 
     /// Explicitly specified [description][2] of this [GraphQL enum value][1].
     ///
-    /// If [`None`], then Rust doc comment is used as [description][2], if any.
+    /// If [`None`], then Rust doc comment will be used as the [description][2],
+    /// if any.
     ///
     /// [1]: https://spec.graphql.org/October2021#sec-Enum-Value
     /// [2]: https://spec.graphql.org/October2021#sec-Descriptions
     description: Option<SpanContainer<String>>,
 
     /// Explicitly specified [deprecation][2] of this [GraphQL enum value][1].
     ///
-    /// If [`None`], then Rust `#[deprecated]` attribute is used as the
+    /// If [`None`], then Rust `#[deprecated]` attribute will be used as the
     /// [deprecation][2], if any.
     ///
     /// If the inner [`Option`] is [`None`], then no [reason][3] was provided.
@@ -357,8 +358,9 @@ struct Definition {
     /// [0]: https://spec.graphql.org/October2021#sec-Enums
     ident: syn::Ident,
 
-    /// [`syn::Generics`] of the Rust enum behind this [GraphQL enum][0].
+    /// [`Generics`] of the Rust enum behind this [GraphQL enum][0].
     ///
+    /// [`Generics`]: syn::Generics
     /// [0]: https://spec.graphql.org/October2021#sec-Enums
     generics: syn::Generics,