[python] Fix empty example value for siblings that share a model (#25106)

toExampleValueRecursive tracks the ancestors of the current schema in
includedSchemas to stop on cycles, but the same list was passed to every
property of an object. When three or more sibling properties referenced
the same model (e.g. inline objects the generator deduplicates into one
model), the third one was mistaken for a cycle and got an empty value,
producing 'prop4 = ,' in the generated tests.

Give each property its own copy of the ancestor list.

Fixes #25047

Author: TanbirRamim

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

@@ -610,8 +610,11 @@ private String toExampleValueRecursive(Schema schema, List<Schema> includedSchem
                         if (StringUtils.isBlank(refTitle) || "null".equals(refTitle)) {
                             schema2.setTitle(propname);
                         }
+                        // Each property gets its own copy of the path: includedSchemas tracks the
+                        // ancestors of the current schema for cycle detection, so siblings that
+                        // reference the same model must not count as a cycle (#25047).
                         example += "\n" + indentationString + underscore(propname) + " = " +
-                                toExampleValueRecursive(schema2, includedSchemas, indentation + 1) + ", ";
+                                toExampleValueRecursive(schema2, new ArrayList<>(includedSchemas), indentation + 1) + ", ";
                     }
                 }
             }

modules/openapi-generator/src/test/java/org/openapitools/codegen/python/PythonClientCodegenTest.java

@@ -217,6 +217,29 @@ public void testGeneratedExampleValues() {
         Assert.assertTrue(codegen.escapeQuotationMark(codegen.toExampleValue(addressSchema)).matches(addressPattern));
     }
 
+    @Test(description = "sibling properties that share a model are not treated as a cycle (#25047)")
+    public void testExampleValueForSiblingsSharingAModel() {
+        final Schema shared = new ObjectSchema().addProperty("prop", new StringSchema());
+        final Schema holder = new ObjectSchema()
+                .addProperty("prop1", new Schema<>().$ref("#/components/schemas/Shared"))
+                .addProperty("prop2", new Schema<>().$ref("#/components/schemas/Shared"))
+                .addProperty("prop3", new Schema<>().$ref("#/components/schemas/Shared"));
+        holder.setTitle("Holder");
+        final OpenAPI openAPI = new OpenAPI().components(new io.swagger.v3.oas.models.Components()
+                .addSchemas("Shared", shared)
+                .addSchemas("Holder", holder));
+        final PythonClientCodegen codegen = new PythonClientCodegen();
+        codegen.setOpenAPI(openAPI);
+
+        final String example = codegen.toExampleValue(holder);
+
+        Assert.assertFalse(example.matches("(?s).*=\\s*,.*"), "empty example value in:\n" + example);
+        for (String prop : Arrays.asList("prop1", "prop2", "prop3")) {
+            Assert.assertTrue(example.contains(prop + " = openapi_client.models.shared.Shared("),
+                    prop + " missing its example in:\n" + example);
+        }
+    }
+
     @Test(description = "test single quotes escape")
     public void testSingleQuotes() {
         final PythonClientCodegen codegen = new PythonClientCodegen();