Fix extra blank lines after custom headers in multiple files (#2638)

Author: koxudaxi

src/datamodel_code_generator/__init__.py

@@ -779,7 +779,7 @@ def get_header_and_first_line(csv_file: IO[str]) -> dict[str, Any]:
                 if header_after:
                     content = header_before + "\n" + extracted_future + "\n\n" + header_after
                 else:
-                    content = header_before + "\n\n\n" + extracted_future
+                    content = header_before + "\n\n" + extracted_future
                 print(content, file=file)
                 print(file=file)
                 print(body_without_future.rstrip(), file=file)

tests/data/expected/main/openapi/custom_file_header.py

@@ -2,7 +2,6 @@
 # header ;
 # file ;
 
-
 from __future__ import annotations
 
 from typing import List, Optional

tests/data/expected/main/openapi/custom_file_header_comments_only.py

@@ -1,7 +1,6 @@
 # Just a comment
 # Another comment
 
-
 from __future__ import annotations
 
 from typing import List, Optional

tests/data/expected/main/openapi/custom_file_header_with_docstring.py

@@ -3,7 +3,6 @@
 This module contains generated models.
 """
 
-
 from __future__ import annotations
 
 from typing import List, Optional

tests/data/expected/main/openapi/modular_all_exports_children_docstring/__init__.py

@@ -4,7 +4,6 @@
 This is a multi-line docstring used for testing.
 """
 
-
 from __future__ import annotations
 
 from ._internal import DifferentTea, Error, Id, OptionalModel, Result, Source

tests/data/expected/main/openapi/modular_all_exports_children_docstring/_internal.py

@@ -4,7 +4,6 @@
 This is a multi-line docstring used for testing.
 """
 
-
 from __future__ import annotations
 
 from typing import List, Optional

tests/data/expected/main/openapi/modular_all_exports_children_docstring/bar.py

@@ -4,7 +4,6 @@
 This is a multi-line docstring used for testing.
 """
 
-
 from __future__ import annotations
 
 from pydantic import BaseModel, Field

tests/data/expected/main/openapi/modular_all_exports_children_docstring/collections.py

@@ -4,7 +4,6 @@
 This is a multi-line docstring used for testing.
 """
 
-
 from __future__ import annotations
 
 from enum import Enum

tests/data/expected/main/openapi/modular_all_exports_children_docstring/foo/__init__.py

@@ -4,7 +4,6 @@
 This is a multi-line docstring used for testing.
 """
 
-
 from __future__ import annotations
 
 from .._internal import Cocoa, Tea

tests/data/expected/main/openapi/modular_all_exports_children_docstring/foo/bar.py

@@ -4,7 +4,6 @@
 This is a multi-line docstring used for testing.
 """
 
-
 from __future__ import annotations
 
 from typing import Any, Dict, List, Optional