Added double option support

Author: ranger-ross

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RustClientCodegen.java

@@ -605,9 +605,18 @@ public void postProcessModelProperty(CodegenModel model, CodegenProperty propert
             additionalProperties.put("serdeWith", true);
         }
 
+        // Add a field for checking if a field is with optional or required in templates.
+        // This is useful in Mustache templates as it's not possible to do OR logic between variables.
+        property.vendorExtensions.put("isMandatory", !property.isNullable && property.required);
+
         // If a property is a base64-encoded byte array, use `serde_with` for deserialization.
         if (property.isByteArray) {
             additionalProperties.put("serdeWith", true);
+            // If a byte array is both nullable and not required we need to include our own
+            // custom double option as serde_as does not work with serde_with's double_option.
+            if (property.isNullable && !property.required) {
+                additionalProperties.put("serdeAsDoubleOption", true);
+            }
         }
     }
 

modules/openapi-generator/src/main/resources/rust/model.mustache

@@ -129,7 +129,7 @@ pub struct {{{classname}}} {
     /// {{{.}}}
     {{/description}}
     {{#isByteArray}}
-    {{#required}}#[serde_as(as = "serde_with::base64::Base64")]{{/required}}{{^required}}#[serde_as(as = "{{#isNullable}}Option<{{/isNullable}}Option<serde_with::base64::Base64>{{#isNullable}}>{{/isNullable}}")]{{/required}}
+    {{#vendorExtensions.isMandatory}}#[serde_as(as = "serde_with::base64::Base64")]{{/vendorExtensions.isMandatory}}{{^vendorExtensions.isMandatory}}#[serde_as(as = "{{^serdeAsDoubleOption}}Option{{/serdeAsDoubleOption}}{{#serdeAsDoubleOption}}super::DoubleOption{{/serdeAsDoubleOption}}<serde_with::base64::Base64>")]{{/vendorExtensions.isMandatory}}
     {{/isByteArray}}
     #[serde(rename = "{{{baseName}}}"{{^required}}{{#isNullable}}, default{{^isByteArray}}, with = "::serde_with::rust::double_option"{{/isByteArray}}{{/isNullable}}{{/required}}{{^required}}, skip_serializing_if = "Option::is_none"{{/required}}{{#required}}{{#isNullable}}, deserialize_with = "Option::deserialize"{{/isNullable}}{{/required}})]
     pub {{{name}}}: {{!

modules/openapi-generator/src/main/resources/rust/model_mod.mustache

@@ -4,3 +4,42 @@ pub mod {{{classFilename}}};
 pub use self::{{{classFilename}}}::{{{classname}}};
 {{/model}}
 {{/models}}
+{{#serdeAsDoubleOption}}
+use serde::{Deserialize, Deserializer, Serializer};
+use serde_with::{de::DeserializeAsWrap, ser::SerializeAsWrap, DeserializeAs, SerializeAs};
+use std::marker::PhantomData;
+
+pub(crate) struct DoubleOption<T>(PhantomData<T>);
+
+impl<T, TAs> SerializeAs<Option<Option<T>>> for DoubleOption<TAs>
+where
+    TAs: SerializeAs<T>,
+{
+    fn serialize_as<S>(values: &Option<Option<T>>, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        match values {
+            None => serializer.serialize_unit(),
+            Some(None) => serializer.serialize_none(),
+            Some(Some(v)) => serializer.serialize_some(&SerializeAsWrap::<T, TAs>::new(v)),
+        }
+    }
+}
+
+impl<'de, T, TAs> DeserializeAs<'de, Option<Option<T>>> for DoubleOption<TAs>
+where
+    TAs: DeserializeAs<'de, T>,
+    T: std::fmt::Debug,
+{
+    fn deserialize_as<D>(deserializer: D) -> Result<Option<Option<T>>, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Ok(Some(
+            DeserializeAsWrap::<Option<T>, Option<TAs>>::deserialize(deserializer)?
+                .into_inner(),
+        ))
+    }
+}
+{{/serdeAsDoubleOption}}