fix: default to None when Option missing (#1092)

Brings the behaviour of `ValueDeserialize` when working with `Option`s in line with serde.
obmarg · Nov 12, 2024 · 2479a51 · 2479a51
1 parent 6a01e8d
commit 2479a51
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Showing 3 changed files with 33 additions and 7 deletions.
diff --git a/cynic-parser-deser-macros/src/lib.rs b/cynic-parser-deser-macros/src/lib.rs
@@ -109,11 +109,14 @@ fn value_deser_impl(ast: syn::DeriveInput) -> Result<TokenStream, ()> {
                     quote! { let #field_name = #field_name.unwrap_or_else(|| #expr); }
                 }
                 None => {
+                    let ty = &field.ty;
                     quote! {
-                        let #field_name = #field_name.ok_or_else(|| cynic_parser_deser::Error::MissingField {
-                            name: #field_name_string.to_string(),
-                            object_span: input.span()
-                        })?;
+                        let #field_name = #field_name
+                            .or(<#ty as ValueDeserialize<#deser_lifetime>>::default_when_missing())
+                            .ok_or_else(|| cynic_parser_deser::Error::MissingField {
+                                name: #field_name_string.to_string(),
+                                object_span: input.span()
+                            })?;
                     }
                 }
             }

diff --git a/cynic-parser-deser/src/deserialize.rs b/cynic-parser-deser/src/deserialize.rs
@@ -5,6 +5,11 @@ use crate::{value::ValueType, ConstDeserializer, DeserValue, Error};
 // ValueDeserialize vs DeserializeValue
 pub trait ValueDeserialize<'a>: Sized {
     fn deserialize(input: DeserValue<'a>) -> Result<Self, Error>;
+
+    /// Provides a default in the case where a field of this type is missing
+    fn default_when_missing() -> Option<Self> {
+        None
+    }
 }
 
 pub trait ValueDeserializeOwned: for<'a> ValueDeserialize<'a> {}
@@ -134,6 +139,10 @@ where
             other => T::deserialize(other).map(Some),
         }
     }
+
+    fn default_when_missing() -> Option<Self> {
+        Some(None)
+    }
 }
 
 impl<'a, T> ValueDeserialize<'a> for Vec<T>

diff --git a/cynic-parser-deser/tests/deser.rs b/cynic-parser-deser/tests/deser.rs
@@ -21,13 +21,13 @@ fn test_struct_default() {
 #[derive(ValueDeserialize)]
 struct FieldDefault {
     #[deser(default)]
-    foo: Option<usize>,
+    foo: usize,
 }
 
 #[test]
 fn test_field_default() {
-    assert_eq!(deser::<FieldDefault>("@id").unwrap().foo, None);
-    assert_eq!(deser::<FieldDefault>("@id(foo: 10)").unwrap().foo, Some(10));
+    assert_eq!(deser::<FieldDefault>("@id").unwrap().foo, 0);
+    assert_eq!(deser::<FieldDefault>("@id(foo: 10)").unwrap().foo, 10);
 }
 
 #[derive(ValueDeserialize)]
@@ -57,6 +57,20 @@ fn test_with() {
     assert_eq!(deser::<WithTest>("@id(foo: 25)").unwrap().foo, 100);
 }
 
+#[derive(ValueDeserialize)]
+struct OptionDefaults {
+    foo: Option<usize>,
+}
+
+#[test]
+fn test_option_defaults() {
+    assert_eq!(deser::<OptionDefaults>("@id").unwrap().foo, None);
+    assert_eq!(
+        deser::<OptionDefaults>("@id(foo: 100)").unwrap().foo,
+        Some(100)
+    );
+}
+
 fn deser<T>(input: &str) -> Result<T, cynic_parser_deser::Error>
 where
     T: ValueDeserializeOwned,