Add skip_serializing_none feature

README.md

@@ -19,6 +19,7 @@ A typed GraphQL client library for Rust.
 - Supports setting GraphQL fields as deprecated and having the Rust compiler check
   their use.
 - Optional reqwest-based client for boilerplate-free API calls from browsers.
+- Implicit and explicit null support.
 
 ## Getting started
 
@@ -107,6 +108,21 @@ use graphql_client::GraphQLQuery;
 )]
 struct UnionQuery;
 ```
+## Implicit Null
+
+The generated code will skip the serialization of `None` values. By default it's `false`.
+
+```rust
+use graphql_client::GraphQLQuery;
+
+#[derive(GraphQLQuery)]
+#[graphql(
+    schema_path = "tests/unions/union_schema.graphql",
+    query_path = "tests/unions/union_query.graphql",
+    skip_serializing_none = "true"
+)]
+struct UnionQuery;
+```
 
 ## Custom scalars
 

graphql_client_codegen/src/codegen/inputs.rs

@@ -3,6 +3,7 @@ use crate::{
     codegen_options::GraphQLClientCodegenOptions,
     query::{BoundQuery, UsedTypes},
     schema::input_is_recursive_without_indirection,
+    type_qualifiers::GraphqlTypeQualifier,
 };
 use heck::ToSnakeCase;
 use proc_macro2::{Ident, Span, TokenStream};
@@ -28,6 +29,11 @@ pub(super) fn generate_input_object_definitions(
                 let normalized_field_type_name = options
                     .normalization()
                     .field_type(field_type.id.name(query.schema));
+                let optional_skip_serializing_none = if *options.skip_serializing_none() && field_type.is_optional() {
+                    Some(quote!(#[serde(skip_serializing_if = "Option::is_none")]))
+                } else {
+                    None
+                };
                 let type_name = Ident::new(normalized_field_type_name.as_ref(), Span::call_site());
                 let field_type_tokens = super::decorate_type(&type_name, &field_type.qualifiers);
                 let field_type = if field_type
@@ -40,12 +46,16 @@ pub(super) fn generate_input_object_definitions(
                 } else {
                     field_type_tokens
                 };
-                quote!(#annotation pub #name_ident: #field_type)
+
+                quote!(
+                    #optional_skip_serializing_none
+                    #annotation pub #name_ident: #field_type
+                )
             });
 
             quote! {
                 #variable_derives
-                pub struct #struct_name {
+                pub struct #struct_name{
                     #(#fields,)*
                 }
             }

graphql_client_codegen/src/codegen/selection.rs

@@ -405,6 +405,18 @@ impl<'a> ExpandedField<'a> {
             qualified_type
         };
 
+        let optional_skip_serializing_none = if *options.skip_serializing_none()
+            && self
+                .field_type_qualifiers
+                .get(0)
+                .map(|qualifier| !qualifier.is_required())
+                .unwrap_or(false)
+        {
+            Some(quote!(#[serde(skip_serializing_if = "Option::is_none")]))
+        } else {
+            None
+        };
+
         let optional_rename = self
             .graphql_name
             .as_ref()
@@ -427,6 +439,7 @@ impl<'a> ExpandedField<'a> {
             };
 
         let tokens = quote! {
+            #optional_skip_serializing_none
             #optional_flatten
             #optional_rename
             #optional_deprecation_annotation

graphql_client_codegen/src/codegen_options.rs

@@ -45,6 +45,8 @@ pub struct GraphQLClientCodegenOptions {
     extern_enums: Vec<String>,
     /// Flag to trigger generation of Other variant for fragments Enum
     fragments_other_variant: bool,
+    /// Skip Serialization of None values.
+    skip_serializing_none: bool,
 }
 
 impl GraphQLClientCodegenOptions {
@@ -65,6 +67,7 @@ impl GraphQLClientCodegenOptions {
             custom_scalars_module: Default::default(),
             extern_enums: Default::default(),
             fragments_other_variant: Default::default(),
+            skip_serializing_none: Default::default(),
         }
     }
 
@@ -214,4 +217,14 @@ impl GraphQLClientCodegenOptions {
     pub fn fragments_other_variant(&self) -> &bool {
         &self.fragments_other_variant
     }
+
+    /// Set the graphql client codegen option's skip none value.
+    pub fn set_skip_serializing_none(&mut self, skip_serializing_none: bool) {
+        self.skip_serializing_none = skip_serializing_none
+    }
+
+    /// Get a reference to the graphql client codegen option's skip none value.
+    pub fn skip_serializing_none(&self) -> &bool {
+        &self.skip_serializing_none
+    }
 }

graphql_client_codegen/src/tests/mod.rs

@@ -117,3 +117,45 @@ fn fragments_other_variant_false_should_not_generate_unknown_other_variant() {
         };
     }
 }
+
+#[test]
+fn skip_serializing_none_should_generate_serde_skip_serializing() {
+    let query_string = include_str!("keywords_query.graphql");
+    let query = graphql_parser::parse_query::<&str>(query_string).expect("Parse keywords query");
+    let schema = graphql_parser::parse_schema(include_str!("keywords_schema.graphql"))
+        .expect("Parse keywords schema")
+        .into_static();
+    let schema = Schema::from(schema);
+
+    let mut options = GraphQLClientCodegenOptions::new(CodegenMode::Cli);
+
+    options.set_skip_serializing_none(true);
+
+    let query = crate::query::resolve(&schema, &query).unwrap();
+
+    for (_id, operation) in query.operations() {
+        let generated_tokens = generated_module::GeneratedModule {
+            query_string,
+            schema: &schema,
+            operation: &operation.name,
+            resolved_query: &query,
+            options: &options,
+        }
+        .to_token_stream()
+        .expect("Generate keywords module");
+
+        let generated_code = generated_tokens.to_string();
+
+        let r: syn::parse::Result<proc_macro2::TokenStream> = syn::parse2(generated_tokens);
+
+        match r {
+            Ok(_) => {
+                println!("{}", generated_code);
+                assert!(generated_code.contains("skip_serializing_if"));
+            }
+            Err(e) => {
+                panic!("Error: {}\n Generated content: {}\n", e, &generated_code);
+            }
+        };
+    }
+}

graphql_query_derive/src/attributes.rs

@@ -103,6 +103,13 @@ pub fn extract_fragments_other_variant(ast: &syn::DeriveInput) -> bool {
         .unwrap_or(false)
 }
 
+pub fn extract_skip_serializing_none(ast: &syn::DeriveInput) -> bool {
+    extract_attr(ast, "skip_serializing_none")
+        .ok()
+        .and_then(|s| FromStr::from_str(s.as_str()).ok())
+        .unwrap_or(false)
+}
+
 #[cfg(test)]
 mod test {
     use super::*;
@@ -219,4 +226,63 @@ mod test {
         let parsed = syn::parse_str(input).unwrap();
         assert!(!extract_fragments_other_variant(&parsed));
     }
+
+    #[test]
+    fn test_skip_serializing_none_set_to_true() {
+        let input = r#"
+            #[derive(GraphQLQuery)]
+            #[graphql(
+                schema_path = "x",
+                query_path = "x",
+                skip_serializing_none = "true"
+            )]
+            struct MyQuery;
+        "#;
+        let parsed = syn::parse_str(input).unwrap();
+        assert!(extract_skip_serializing_none(&parsed));
+    }
+
+    #[test]
+    fn test_skip_serializing_none_set_to_false() {
+        let input = r#"
+            #[derive(GraphQLQuery)]
+            #[graphql(
+                schema_path = "x",
+                query_path = "x",
+                skip_serializing_none = "false"
+            )]
+            struct MyQuery;
+        "#;
+        let parsed = syn::parse_str(input).unwrap();
+        assert!(!extract_skip_serializing_none(&parsed));
+    }
+
+    #[test]
+    fn test_skip_serializing_none_set_to_invalid() {
+        let input = r#"
+            #[derive(GraphQLQuery)]
+            #[graphql(
+                schema_path = "x",
+                query_path = "x",
+                skip_serializing_none = "invalid"
+            )]
+            struct MyQuery;
+        "#;
+        let parsed = syn::parse_str(input).unwrap();
+        assert!(!extract_skip_serializing_none(&parsed));
+    }
+
+    #[test]
+    fn test_skip_serializing_none_unset() {
+        let input = r#"
+            #[derive(GraphQLQuery)]
+            #[graphql(
+                schema_path = "x",
+                query_path = "x",
+            )]
+            struct MyQuery;
+        "#;
+        let parsed = syn::parse_str(input).unwrap();
+        assert!(!extract_skip_serializing_none(&parsed));
+    }
 }

graphql_query_derive/src/lib.rs

@@ -64,10 +64,12 @@ fn build_graphql_client_derive_options(
     let custom_scalars_module = attributes::extract_attr(input, "custom_scalars_module").ok();
     let extern_enums = attributes::extract_attr_list(input, "extern_enums").ok();
     let fragments_other_variant: bool = attributes::extract_fragments_other_variant(input);
+    let skip_serializing_none: bool = attributes::extract_skip_serializing_none(input);
 
     let mut options = GraphQLClientCodegenOptions::new(CodegenMode::Derive);
     options.set_query_file(query_path);
     options.set_fragments_other_variant(fragments_other_variant);
+    options.set_skip_serializing_none(skip_serializing_none);
 
     if let Some(variables_derives) = variables_derives {
         options.set_variables_derives(variables_derives);