fix: Internal error when Open API 2.0 schema contains no swagger key

Signed-off-by: Dmitry Dygalo <dmitry@dygalo.dev>

docs/changelog.rst

@@ -9,6 +9,7 @@ Changelog
 - Not respecting ``allow_x00`` and ``codec`` configs options during filling gaps in explicit examples.
 - Internal error when sending ``multipart/form-data`` requests when the schema defines the ``*/*`` content type.
 - Internal error when YAML payload definition contains nested ``binary`` format.
+- Internal error when an Open API 2.0 schema contains no ``swagger`` key and the schema version is forced.
 
 **Changed**
 

src/schemathesis/runner/events.py

@@ -205,6 +205,9 @@ class InternalErrorType(str, enum.Enum):
     OTHER = "other"
 
 
+DEFAULT_INTERNAL_ERROR_MESSAGE = "An internal error occurred during the test run"
+
+
 @dataclass
 class InternalError(ExecutionEvent):
     """An error that happened inside the runner."""
@@ -243,7 +246,7 @@ def from_exc(cls, exc: Exception) -> InternalError:
             type_=InternalErrorType.OTHER,
             subtype=None,
             title="Test Execution Error",
-            message="An internal error occurred during the test run",
+            message=DEFAULT_INTERNAL_ERROR_MESSAGE,
             extras=[],
         )
 

src/schemathesis/specs/openapi/schemas.py

@@ -809,7 +809,7 @@ class SwaggerV20(BaseOpenAPISchema):
 
     @property
     def spec_version(self) -> str:
-        return self.raw_schema["swagger"]
+        return self.raw_schema.get("swagger", "2.0")
 
     @property
     def verbose_name(self) -> str:

test/cli/test_crashes.py

@@ -10,6 +10,7 @@
 from schemathesis.cli import ALL_CHECKS_NAMES, ALL_TARGETS_NAMES
 from schemathesis.code_samples import CodeSampleStyle
 from schemathesis.fixups import ALL_FIXUPS
+from schemathesis.runner.events import DEFAULT_INTERNAL_ERROR_MESSAGE
 from schemathesis.stateful import Stateful
 
 
@@ -132,7 +133,7 @@ def csv_strategy(enum):
 @pytest.mark.usefixtures("mocked_schema")
 def test_valid_parameters_combos(cli, schema_url, params, flags, multiple_params, csv_params, tmp_path):
     report = tmp_path / "temp.tar.gz"
-    result = cli.run(schema_url, *params, *multiple_params, *flags, *csv_params, f"--report={report}")
+    result = cli.run(schema_url, *params, *multiple_params, *flags, *csv_params, f"--report={report}", "--show-trace")
     check_result(result)
 
 
@@ -156,6 +157,7 @@ def test_schema_validity(cli, schema, base_url):
 
 def check_result(result):
     assert not (result.exception and not isinstance(result.exception, SystemExit)), result.stdout
+    assert DEFAULT_INTERNAL_ERROR_MESSAGE not in result.stdout, result.stdout
 
 
 def test_not_handled_error(mocker, cli, schema_url):