Escape generated pyproject TOML strings (#3436)

* Escape generated pyproject TOML strings

* Mark TOML escaping test as allow_direct_assert

The assert-helper guard test rejects direct assert statements in guarded
modules. This unit test verifies a TOML round-trip rather than comparing
generated output via shared helpers, so the narrow marker exception fits.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Test TOML escaping via e2e golden-file comparison

Replace the unit-style direct-assert test with run_main_with_args against
a golden fixture, matching the other generate-pyproject-config tests. This
exercises the full CLI path and drops the need for the allow_direct_assert
marker the assert-helper guard would otherwise require.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: DarkaMaul

src/datamodel_code_generator/__main__.py

@@ -629,7 +629,7 @@ def _format_toml_value(value: TomlValue) -> str:
     if isinstance(value, bool):
         return "true" if value else "false"
     if isinstance(value, str):
-        return f'"{value}"'
+        return json.dumps(value, ensure_ascii=False)
     formatted_items = [_format_toml_value(item) for item in value]
     return f"[{', '.join(formatted_items)}]"
 

tests/data/expected/main_kr/generate_pyproject_config/escapes_toml_strings.txt

@@ -0,0 +1,5 @@
+[tool.datamodel-codegen]
+custom-file-header = "say \"hi\" on C:\\tmp\nnext"
+http-headers = ["Authorization: Bearer \"abc\"", "X-Path: C:\\tmp"]
+input = "schema.yaml"
+

tests/test_main_kr.py

@@ -827,6 +827,24 @@ def test_generate_pyproject_config_with_enum_option(capsys: pytest.CaptureFixtur
     )
 
 
+def test_generate_pyproject_config_escapes_toml_strings(capsys: pytest.CaptureFixture[str]) -> None:
+    """Test --generate-pyproject-config escapes special characters in TOML basic strings."""
+    run_main_with_args(
+        [
+            "--generate-pyproject-config",
+            "--input",
+            "schema.yaml",
+            "--custom-file-header",
+            'say "hi" on C:\\tmp\nnext',
+            "--http-headers",
+            'Authorization: Bearer "abc"',
+            "X-Path: C:\\tmp",
+        ],
+        capsys=capsys,
+        expected_stdout_path=EXPECTED_GENERATE_PYPROJECT_CONFIG_PATH / "escapes_toml_strings.txt",
+    )
+
+
 EXPECTED_GENERATE_CLI_COMMAND_PATH = EXPECTED_MAIN_KR_PATH / "generate_cli_command"