Address review findings

Author: bartosz822

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaHttp4sClientCodegen.java

@@ -88,6 +88,9 @@ public ScalaHttp4sClientCodegen() {
                         SchemaSupportFeature.Polymorphism,
                         SchemaSupportFeature.not
                 )
+                .includeSchemaSupportFeatures(
+                        SchemaSupportFeature.oneOf
+                )
                 .excludeParameterFeatures(
                         ParameterFeature.Cookie,
                         ParameterFeature.FormMultipart
@@ -390,8 +393,10 @@ public Map<String, ModelsMap> postProcessAllModels(Map<String, ModelsMap> objs)
                     Set<String> additionalImports = new HashSet<>();
                     for (String childName : cModel.oneOf) {
                         CodegenModel childModel = allModels.get(childName);
-                        if (childModel != null && oneOfMemberCount.getOrDefault(childName, 0) == 1) {
-                            // Mark for inlining (only used by this one parent)
+                        if (childModel != null
+                                && (childModel.oneOf == null || childModel.oneOf.isEmpty())
+                                && oneOfMemberCount.getOrDefault(childName, 0) == 1) {
+                            // Mark for inlining (only used by this one parent, and not itself a oneOf container)
                             childModel.getVendorExtensions().put("x-isOneOfMember", true);
                             childModel.getVendorExtensions().put("x-oneOfParent", cModel.classname);
                             // Store parent's discriminator info for use in template
@@ -407,6 +412,20 @@ public Map<String, ModelsMap> postProcessAllModels(Map<String, ModelsMap> objs)
                         }
                     }
 
+                    // Create list of discriminator entries with class names and schema names
+                    // When discriminator has no explicit mapping, use schema name (not class name)
+                    List<Map<String, String>> discriminatorEntries = new ArrayList<>();
+                    for (String childName : cModel.oneOf) {
+                        CodegenModel childModel = allModels.get(childName);
+                        if (childModel != null) {
+                            Map<String, String> entry = new HashMap<>();
+                            entry.put("classname", childModel.classname);
+                            entry.put("schemaName", childModel.name);
+                            discriminatorEntries.add(entry);
+                        }
+                    }
+                    cModel.getVendorExtensions().put("x-discriminator-entries", discriminatorEntries);
+
                     // Decide between sealed trait (with inlined members) vs regular trait (edge cases)
                     // Use sealed trait ONLY if ALL oneOf members can be inlined
                     // If some are inlined and some aren't (mixed case), use regular trait

modules/openapi-generator/src/main/resources/scala-http4s/model.mustache

@@ -43,16 +43,16 @@ object {{classname}} {
 {{^vendorExtensions.x-use-discr-mapping}}
 // with discriminator, no mapping
   given encoder{{classname}}: Encoder[{{classname}}] = Encoder.instance {
-{{#oneOf}}
-    case obj: {{.}} => obj.asJson.mapObject(("{{discriminator.propertyName}}" -> "{{.}}".asJson) +: _)
-{{/oneOf}}
+{{#vendorExtensions.x-discriminator-entries}}
+    case obj: {{classname}} => obj.asJson.mapObject(("{{discriminator.propertyName}}" -> "{{schemaName}}".asJson) +: _)
+{{/vendorExtensions.x-discriminator-entries}}
   }
 
   given decoder{{classname}}: Decoder[{{classname}}] = Decoder.instance { cursor =>
     cursor.downField("{{discriminator.propertyName}}").as[String].flatMap {
-      {{#oneOf}}
-      case "{{.}}" => cursor.as[{{.}}]
-      {{/oneOf}}
+      {{#vendorExtensions.x-discriminator-entries}}
+      case "{{schemaName}}" => cursor.as[{{classname}}]
+      {{/vendorExtensions.x-discriminator-entries}}
       case discriminatorValue =>
         Left(DecodingFailure(s"Unknown discriminator value: $discriminatorValue", cursor.history))
     }
@@ -109,14 +109,14 @@ object {{classname}} {
 // with discriminator, no mapping
   given encoder{{classname}}: Encoder[{{classname}}] = Encoder.instance {
 {{#vendorExtensions.x-oneOfMembers}}
-    case obj: {{classname}} => obj.asJson.mapObject(("{{vendorExtensions.x-parentDiscriminatorName}}" -> "{{classname}}".asJson) +: _)
+    case obj: {{classname}} => obj.asJson.mapObject(("{{vendorExtensions.x-parentDiscriminatorName}}" -> "{{name}}".asJson) +: _)
 {{/vendorExtensions.x-oneOfMembers}}
   }
 
   given decoder{{classname}}: Decoder[{{classname}}] = Decoder.instance { cursor =>
     cursor.downField("{{discriminator.propertyName}}").as[String].flatMap {
       {{#vendorExtensions.x-oneOfMembers}}
-      case "{{classname}}" => cursor.as[{{classname}}]
+      case "{{name}}" => cursor.as[{{classname}}]
       {{/vendorExtensions.x-oneOfMembers}}
       case discriminatorValue =>
         Left(DecodingFailure(s"Unknown discriminator value: $discriminatorValue", cursor.history))