[Protobuf] Improve oneOf Handling by Unwrapping allOf for Complex Types (#22700)

* Improve Protobuf Generator's oneOf Handling allOf Unwrapping with Complex Types

* Address cubic-dev-ai comment

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

@@ -442,7 +442,19 @@ public class ProtobufSchemaCodegen extends DefaultCodegen implements CodegenConf
             List<Schema> oneOfs = schema.getOneOf();
             List<Schema> newOneOfs = new ArrayList<>();
             for (Schema oneOf : oneOfs) {
-                Schema oneOfSchema = ModelUtils.getReferencedSchema(openAPI, oneOf);
+                Schema oneOfSchema = oneOf;
+                if (ModelUtils.isAllOf(oneOf) && oneOf.getAllOf() != null && oneOf.getAllOf().size() == 1) {
+                    Object allOfObj = oneOf.getAllOf().get(0);
+                    if (allOfObj instanceof Schema) {
+                        Schema allOfItem = (Schema) allOfObj;
+                        if (StringUtils.isNotEmpty(allOfItem.get$ref())) {
+                            oneOfSchema = ModelUtils.getReferencedSchema(openAPI, allOfItem);
+                        }
+                    }
+                } else {
+                    oneOfSchema = ModelUtils.getReferencedSchema(openAPI, oneOf);
+                }
+
                 if (ModelUtils.isArraySchema(oneOfSchema)) {
                     Schema innerSchema = generateNestedSchema(oneOfSchema, visitedSchemas);
                     innerSchema.setTitle(oneOf.getTitle());

modules/openapi-generator/src/test/java/org/openapitools/codegen/protobuf/ProtobufSchemaCodegenTest.java

@@ -18,8 +18,10 @@ package org.openapitools.codegen.protobuf;
 
 import io.swagger.v3.oas.models.OpenAPI;
 import io.swagger.v3.oas.models.media.ArraySchema;
+import io.swagger.v3.oas.models.media.BooleanSchema;
 import io.swagger.v3.oas.models.media.IntegerSchema;
 import io.swagger.v3.oas.models.media.MapSchema;
+import io.swagger.v3.oas.models.media.NumberSchema;
 import io.swagger.v3.oas.models.media.ObjectSchema;
 import io.swagger.v3.oas.models.media.Schema;
 import io.swagger.v3.oas.models.media.StringSchema;
@@ -45,6 +47,7 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 
+
 import static org.openapitools.codegen.TestUtils.createCodegenModelWrapper;
 import static org.openapitools.codegen.languages.ProtobufSchemaCodegen.USE_SIMPLIFIED_ENUM_NAMES;
 import static org.testng.Assert.assertEquals;
@@ -142,6 +145,64 @@ public class ProtobufSchemaCodegenTest {
         output.deleteOnExit();
     }
 
+    @Test
+    public void testCodeGenWithOneOfDiscriminator31() throws IOException {
+        System.setProperty("line.separator", "\n");
+
+        File output = Files.createTempDirectory("test").toFile();
+
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName("protobuf-schema")
+                .setInputSpec("src/test/resources/3_1/oneOf.yaml")
+                .setOutputDir(output.getAbsolutePath().replace("\\", "/"));
+
+        final ClientOptInput clientOptInput = configurator.toClientOptInput();
+        DefaultGenerator generator = new DefaultGenerator();
+        List<File> files = generator.opts(clientOptInput).generate();
+
+        TestUtils.ensureContainsFile(files, output, "models/fruit.proto");
+
+        // Get the processed OpenAPI with wrapper schemas
+        OpenAPI openAPI = clientOptInput.getOpenAPI();
+        ProtobufSchemaCodegen codegen = new ProtobufSchemaCodegen();
+        codegen.setOpenAPI(openAPI);
+        codegen.processOpts();
+
+        Schema fruitSchema = openAPI.getComponents().getSchemas().get("fruit");
+        Assert.assertNotNull(fruitSchema, "fruit schema should exist");
+
+        CodegenModel fruitModel = codegen.fromModel("fruit", fruitSchema);
+        codegen.postProcessModels(createCodegenModelWrapper(fruitModel));
+
+        Assert.assertNotNull(fruitModel.oneOf, "fruit model should have oneOf items");
+        Assert.assertTrue(fruitModel.oneOf.size() >= 2, "fruit model should have at least 2 oneOf items");
+
+        Assert.assertNotNull(fruitModel.vars, "fruit model should have vars");
+        Assert.assertTrue(fruitModel.vars.size() > 0, "fruit model should have at least one var");
+
+        Assert.assertEquals(fruitModel.vars.size(), 3, "fruit model should have 3 vars (one for each oneOf item)");
+
+        for (CodegenProperty var : fruitModel.vars) {
+            Assert.assertNotNull(var.name, "var name should not be null");
+            Assert.assertNotNull(var.dataType, "var dataType should not be null");
+            Assert.assertTrue(var.isModel, "var " + var.name + " should be a model type (isModel=" + var.isModel + ")");
+            Assert.assertFalse(var.isContainer, "var should not be a container (it references a model)");
+
+            // Check expected properties based on discriminator title
+            if (var.name.equals("apple_list")) {
+                Assert.assertEquals(var.dataType, "StringArray", "apple_list should reference StringArray");
+            } else if (var.name.equals("banana_map")) {
+                Assert.assertEquals(var.dataType, "FloatMap", "banana_map should reference FloatMap");
+            } else if (var.name.equals("orange_choice")) {
+                Assert.assertEquals(var.dataType, "Orange", "orange_choice should reference Orange");
+            } else {
+                Assert.fail("Unexpected var name: " + var.name + ". Expected one of: apple_list, banana_map, orange_choice");
+            }
+        }
+
+        output.deleteOnExit();
+    }
+
     @Test(description = "convert a model with dollar signs")
     public void modelTest() {
         final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/dollar-in-names-pull14359.yaml");

modules/openapi-generator/src/test/resources/3_1/oneOf.yaml

@@ -0,0 +1,42 @@
+openapi: 3.1.0
+
+info:
+  title: fruity
+  version: 0.0.1
+
+paths:
+  /:
+    get:
+      responses:
+        '200':
+          description: desc
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/fruit'
+
+components:
+  schemas:
+    fruit:
+      oneOf:
+        - title: appleList
+          $ref: '#/components/schemas/appleArray'
+        - title: bananaMap
+          $ref: '#/components/schemas/bananaMap'
+        - title: orangeChoice
+          $ref: '#/components/schemas/orange'
+    appleArray:
+      type: array
+      items:
+        title: appleaArray
+        type: string
+    bananaMap:
+      type: object
+      additionalProperties:
+        type: number
+    orange:
+      title: orange
+      type: object
+      properties:
+        sweet:
+          type: boolean