From a0a6cd69b2753acbfd0821912c2fd0811f80d934 Mon Sep 17 00:00:00 2001
From: Roman Imankulov <roman.imankulov@gmail.com>
Date: Thu, 20 Jul 2023 16:42:42 +0100
Subject: [PATCH] Fix "parent" AttributeError when calling
 --collapse-root-models (#1432)

Fixes #1419
---
 datamodel_code_generator/parser/base.py       |  4 ++-
 .../output.py                                 | 13 ++++++++++
 tests/data/openapi/flat_type.jsonschema       | 16 ++++++++++++
 tests/test_main.py                            | 25 +++++++++++++++++++
 4 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 tests/data/expected/main/main_collapse_root_models_with_references_to_flat_types/output.py
 create mode 100644 tests/data/openapi/flat_type.jsonschema

diff --git a/datamodel_code_generator/parser/base.py b/datamodel_code_generator/parser/base.py
index e5a03bbe3..b8903bd65 100644
--- a/datamodel_code_generator/parser/base.py
+++ b/datamodel_code_generator/parser/base.py
@@ -868,7 +868,9 @@ def __collapse_root_models(
                     data_type.remove_reference()
 
                     root_type_model.reference.children = [
-                        c for c in root_type_model.reference.children if c.parent
+                        c
+                        for c in root_type_model.reference.children
+                        if getattr(c, 'parent', None)
                     ]
 
                     if not root_type_model.reference.children:
diff --git a/tests/data/expected/main/main_collapse_root_models_with_references_to_flat_types/output.py b/tests/data/expected/main/main_collapse_root_models_with_references_to_flat_types/output.py
new file mode 100644
index 000000000..0e6eff78e
--- /dev/null
+++ b/tests/data/expected/main/main_collapse_root_models_with_references_to_flat_types/output.py
@@ -0,0 +1,13 @@
+# generated by datamodel-codegen:
+#   filename:  flat_type.jsonschema
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import Optional
+
+from pydantic import BaseModel
+
+
+class FooModel(BaseModel):
+    foo: Optional[str] = None
diff --git a/tests/data/openapi/flat_type.jsonschema b/tests/data/openapi/flat_type.jsonschema
new file mode 100644
index 000000000..9be8e2bf2
--- /dev/null
+++ b/tests/data/openapi/flat_type.jsonschema
@@ -0,0 +1,16 @@
+{
+  "title": "Foo",
+  "$schema": "http://json-schema.org/schema#",
+  "description": "",
+  "type": "object",
+  "properties": {
+    "foo": {
+      "$ref": "#/definitions/foo"
+    }
+  },
+  "definitions": {
+    "foo": {
+      "type": "string"
+    }
+  }
+}
diff --git a/tests/test_main.py b/tests/test_main.py
index 218ad45c4..7c3a5a3c5 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -4339,6 +4339,31 @@ def test_main_collapse_root_models_field_constraints():
         )
 
 
+@freeze_time('2019-07-26')
+def test_main_collapse_root_models_with_references_to_flat_types():
+    with TemporaryDirectory() as output_dir:
+        output_file: Path = Path(output_dir) / 'output.py'
+        return_code: Exit = main(
+            [
+                '--input',
+                str(OPEN_API_DATA_PATH / 'flat_type.jsonschema'),
+                '--output',
+                str(output_file),
+                '--collapse-root-models',
+            ]
+        )
+
+        assert return_code == Exit.OK
+        assert (
+            output_file.read_text()
+            == (
+                EXPECTED_MAIN_PATH
+                / 'main_collapse_root_models_with_references_to_flat_types'
+                / 'output.py'
+            ).read_text()
+        )
+
+
 @freeze_time('2019-07-26')
 def test_main_openapi_max_items_enum():
     with TemporaryDirectory() as output_dir: