fix #22147 handle rust generating null

Author: JensWalter

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

@@ -308,6 +308,9 @@ public CodegenModel fromModel(String name, Schema model) {
                     // In-placed type (primitive), because there is no mapping or ref for it.
                     // use camelized `title` if present, otherwise use `type`
                     String oneOfName = Optional.ofNullable(schema.getTitle()).orElseGet(schema::getType);
+                    if (oneOfName == null) {
+                        oneOfName = "Variant" + i;
+                    }
                     oneOf.setName(toModelName(oneOfName));
                 }
             }

modules/openapi-generator/src/test/java/org/openapitools/codegen/rust/RustClientCodegenTest.java

@@ -271,4 +271,22 @@ public void testMultipleArrayTypesEnum() throws IOException {
         TestUtils.assertFileExists(outputPath);
         TestUtils.assertFileContains(outputPath, enumSpec);
     }
+
+    @Test
+    public void testAnonymousOneOfGeneratesRustModel() throws IOException {
+        Path target = Files.createTempDirectory("test_anonymous_one_of");
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName("rust")
+                .setInputSpec("src/test/resources/3_0/rust/rust-anonymous-oneof-model.yaml")
+                .setOutputDir(target.toAbsolutePath().toString().replace("\\", "/"));
+
+        try {
+            List<File> files = new DefaultGenerator().opts(configurator.toClientOptInput()).generate();
+            files.forEach(File::deleteOnExit);
+            Path outputPath = Path.of(target.toString(), "/src/models/custom_fields_attributes.rs");
+            TestUtils.assertFileExists(outputPath);
+        } finally {
+            target.toFile().deleteOnExit();
+        }
+    }
 }

modules/openapi-generator/src/test/resources/3_0/rust/rust-anonymous-oneof-model.yaml

@@ -0,0 +1,50 @@
+openapi: 3.1.0
+info:
+  title: Rust Anonymous OneOf Model
+  version: 1.0.0
+paths:
+  /example:
+    patch:
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              properties:
+                custom_fields_attributes:
+                  $ref: "#/components/schemas/custom_fields_attributes"
+      responses:
+        "200":
+          description: Success
+          content:
+            application/json:
+              schema:
+                type: object
+components:
+  schemas:
+    custom_fields_attributes:
+      oneOf:
+        - type: object
+          additionalProperties:
+            type: object
+            properties:
+              id:
+                type:
+                  - integer
+                  - string
+              value:
+                type: string
+            required:
+              - id
+              - value
+        - type: array
+          items:
+            type: object
+            properties:
+              id:
+                type:
+                  - integer
+                  - string
+              value:
+                type: string