Fix missing constr import issue

Add duplicate field constraints test case

datamodel_code_generator/parser/base.py

@@ -873,6 +873,7 @@ def __collapse_root_models(
                         ]
                     else:  # pragma: no cover
                         continue
+                    imports.append(copied_data_type.imports)
 
                     data_type.remove_reference()
 

tests/data/expected/main/duplicate_field_constraints/common.py

@@ -0,0 +1,13 @@
+# generated by datamodel-codegen:
+#   filename:  common.yml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import Any
+
+from pydantic import RootModel
+
+
+class Model(RootModel[Any]):
+    root: Any

tests/data/expected/main/duplicate_field_constraints/test.py

@@ -0,0 +1,15 @@
+# generated by datamodel-codegen:
+#   filename:  test.yml
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from pydantic import BaseModel, Field, constr
+
+from . import common
+
+
+class Test(BaseModel):
+    uid: constr(pattern=r'[0-9ABCDEFGHJKMNPQRSTVWXYZ]{26,26}') = Field(
+        ..., description='ulid of this object'
+    )

tests/data/jsonschema/duplicate_field_constraints/common.yml

@@ -0,0 +1,7 @@
+---
+$schema: https://json-schema.org/draft/2020-12/schema
+$id: common.yml
+definitions:
+  ulid:
+    type: string
+    pattern: '[0-9ABCDEFGHJKMNPQRSTVWXYZ]{26,26}'

tests/data/jsonschema/duplicate_field_constraints/test.yml

@@ -0,0 +1,10 @@
+---
+$schema: https://json-schema.org/draft/2020-12/schema
+$id: test.yml
+title: test
+required:
+  - uid
+properties:
+  uid:
+    description: ulid of this object
+    $ref: ./common.yml#/definitions/ulid

tests/test_main.py

@@ -5804,3 +5804,29 @@ def test_main_msgspec_use_annotated_with_field_constraints():
                 / 'output.py'
             ).read_text()
         )
+
+
+@freeze_time('2019-07-26')
+def test_main_duplicate_field_constraints():
+    with TemporaryDirectory() as output_dir:
+        output_path: Path = Path(output_dir)
+        return_code: Exit = main(
+            [
+                '--input',
+                str(JSON_SCHEMA_DATA_PATH / 'duplicate_field_constraints'),
+                '--output',
+                str(output_path),
+                '--input-file-type',
+                'jsonschema',
+                '--collapse-root-models',
+                '--output-model-type',
+                'pydantic_v2.BaseModel',
+            ]
+        )
+        assert return_code == Exit.OK
+        main_modular_dir = EXPECTED_MAIN_PATH / 'duplicate_field_constraints'
+        for path in main_modular_dir.rglob('*.py'):
+            result = output_path.joinpath(
+                path.relative_to(main_modular_dir)
+            ).read_text()
+            assert result == path.read_text()