Fix attributes in allOf and $ref

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

@@ -3979,6 +3979,8 @@ public CodegenProperty fromProperty(String name, Schema p, boolean required, boo
             } else {
                 LOGGER.error("Unknown type in allOf schema. Please report the issue via openapi-generator's Github issue tracker.");
             }
+        } else if (p.get$ref() != null) { // it's a ref
+            original = p;
         }
 
         CodegenProperty property = CodegenModelFactory.newInstance(CodegenModelType.PROPERTY);
@@ -4214,6 +4216,24 @@ public CodegenProperty fromProperty(String name, Schema p, boolean required, boo
             if (original.getDescription() != null) {
                 property.description = p.getDescription();
             }
+            if (original.getMaxLength() != null) {
+                property.setMaxLength(original.getMaxLength());
+            }
+            if (original.getMinLength() != null) {
+                property.setMinLength(original.getMinLength());
+            }
+            if (original.getMaxItems() != null) {
+                property.setMaxItems(original.getMaxItems());
+            }
+            if (original.getMinItems() != null) {
+                property.setMinItems(original.getMinItems());
+            }
+            if (original.getMaximum() != null) {
+                property.setMaximum(String.valueOf(original.getMaximum().doubleValue()));
+            }
+            if (original.getMinimum() != null) {
+                property.setMinimum(String.valueOf(original.getMinimum().doubleValue()));
+            }
         }
 
         // set the default value

modules/openapi-generator/src/test/java/org/openapitools/codegen/kotlin/KotlinServerCodegenTest.java

@@ -5,6 +5,7 @@
 import org.openapitools.codegen.DefaultGenerator;
 import org.openapitools.codegen.TestUtils;
 import org.openapitools.codegen.languages.KotlinServerCodegen;
+import org.openapitools.codegen.languages.KotlinSpringServerCodegen;
 
 import java.io.File;
 import java.io.IOException;
@@ -164,4 +165,26 @@ public void beanValidationJakartaEeImports() throws IOException {
                 "import javax.validation.Valid"
         );
     }
+
+    // to test attributes in the $ref (OpenAPI 3.1 spec)
+    @Test
+    public void attributesInRef() throws IOException {
+        File output = Files.createTempDirectory("test_attributes").toFile().getCanonicalFile();
+        output.deleteOnExit();
+
+        KotlinSpringServerCodegen codegen = new KotlinSpringServerCodegen();
+        codegen.setOutputDir(output.getAbsolutePath());
+
+        new DefaultGenerator().opts(new ClientOptInput()
+                        .openAPI(TestUtils.parseSpec("src/test/resources/3_1/issue_17726.yaml"))
+                        .config(codegen))
+                .generate();
+
+        String outputPath = output.getAbsolutePath() + "src/main/kotlin/org/openapitools";
+        Path order = Paths.get(outputPath + "/model/Order.kt");
+        assertFileContains(
+                order,
+                "@get:Size(max=50)"
+        );
+    }
 }

modules/openapi-generator/src/test/resources/3_1/issue_17726.yaml

@@ -0,0 +1,24 @@
+openapi: 3.1.0
+info:
+  title: dummy
+  version: "1.0"
+paths:
+  /users/{id}:
+    summary: Represents a user
+components:
+  schemas:
+    Order:
+      type: object
+      required:
+        - name
+      properties:
+        name:
+          type: string
+        address:
+          $ref: '#/components/schemas/Address'
+          maxLength: 50
+    Address:
+      type: object
+      properties:
+        firstName:
+          type: string