fix: Internal error on unresolvable Open API links

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

docs/changelog.rst

@@ -4,6 +4,10 @@ Changelog
 :version:`Unreleased <v3.28.0...HEAD>` - TBD
 --------------------------------------------
 
+**Fixed**
+
+- Internal error on unresolvable Open API links during stateful testing.
+
 **Performance**
 
 - Improve performance of ``add_link`` by avoiding unnecessary reference resolving.

src/schemathesis/specs/openapi/links.py

@@ -4,22 +4,22 @@
 """
 
 from __future__ import annotations
+
 from dataclasses import dataclass, field
 from difflib import get_close_matches
-from typing import Any, Generator, NoReturn, Sequence, Union, TYPE_CHECKING
+from typing import TYPE_CHECKING, Any, Generator, NoReturn, Sequence, Union
 
+from ...constants import NOT_SET
+from ...internal.copy import fast_deepcopy
 from ...models import APIOperation, Case
 from ...parameters import ParameterSet
-from ...stateful import ParsedData, StatefulTest
+from ...stateful import ParsedData, StatefulTest, UnresolvableLink
 from ...stateful.state_machine import Direction
 from ...types import NotSet
-
-from ...constants import NOT_SET
-from ...internal.copy import fast_deepcopy
 from . import expressions
 from .constants import LOCATION_TO_CONTAINER
 from .parameters import OpenAPI20Body, OpenAPI30Body, OpenAPIParameter
-
+from .references import Unresolvable
 
 if TYPE_CHECKING:
     from ...transports.responses import GenericResponse
@@ -61,16 +61,17 @@ def from_definition(cls, name: str, definition: dict[str, dict[str, Any]], sourc
     def parse(self, case: Case, response: GenericResponse) -> ParsedData:
         """Parse data into a structure expected by links definition."""
         context = expressions.ExpressionContext(case=case, response=response)
-        parameters = {
-            parameter: expressions.evaluate(expression, context) for parameter, expression in self.parameters.items()
-        }
-        return ParsedData(
-            parameters=parameters,
-            # https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.3.md#link-object
-            # > A literal value or {expression} to use as a request body when calling the target operation.
-            # In this case all literals will be passed as is, and expressions will be evaluated
-            body=expressions.evaluate(self.request_body, context),
-        )
+        parameters = {}
+        for parameter, expression in self.parameters.items():
+            evaluated = expressions.evaluate(expression, context)
+            if isinstance(evaluated, Unresolvable):
+                raise UnresolvableLink(f"Unresolvable reference in the link: {expression}")
+            parameters[parameter] = evaluated
+        # https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.3.md#link-object
+        # > A literal value or {expression} to use as a request body when calling the target operation.
+        # In this case all literals will be passed as is, and expressions will be evaluated
+        body = expressions.evaluate(self.request_body, context)
+        return ParsedData(parameters=parameters, body=body)
 
     def make_operation(self, collected: list[ParsedData]) -> APIOperation:
         """Create a modified version of the original API operation with additional data merged in."""

src/schemathesis/specs/openapi/stateful/__init__.py

@@ -10,8 +10,7 @@
 from ....stateful.state_machine import APIStateMachine, Direction, StepResult
 from ....utils import combine_strategies
 from .. import expressions
-from . import links
-from .links import APIOperationConnections, Connection, _convert_strategy, apply, make_response_filter
+from .links import APIOperationConnections, Connection, apply
 
 if TYPE_CHECKING:
     from ....models import APIOperation, Case

src/schemathesis/stateful/__init__.py

@@ -16,6 +16,10 @@
     from .state_machine import APIStateMachine
 
 
+class UnresolvableLink(Exception):
+    """Raised when a link cannot be resolved."""
+
+
 @enum.unique
 class Stateful(enum.Enum):
     none = 1
@@ -70,8 +74,12 @@ def make_operation(self) -> APIOperation:
 
     def store(self, case: Case, response: GenericResponse) -> None:
         """Parse and store data for a stateful test."""
-        parsed = self.stateful_test.parse(case, response)
-        self.container.append(parsed)
+        try:
+            parsed = self.stateful_test.parse(case, response)
+            self.container.append(parsed)
+        except UnresolvableLink:
+            # For now, ignore if a link cannot be resolved
+            pass
 
 
 @dataclass

test/cli/__snapshots__/test_commands/test_unresolvable_links[Open API 3.0].raw

@@ -0,0 +1,29 @@
+Exit code: 0
+---
+Stdout:
+======================= Schemathesis test session starts =======================
+Schema location: file:///tmp/schema.json
+Base URL: http://127.0.0.1/api
+Specification version: Open API 3.0.2
+Random seed: 42
+Workers: 1
+Collected API operations: 3
+Collected API links: 2
+API probing: SUCCESS
+Schema analysis: SKIP
+
+POST /api/users/ .                                                        [ 33%]
+    -> GET /api/users/{user_id} .                                         [ 50%]
+    -> PATCH /api/users/{user_id} .                                       [ 60%]
+GET /api/users/{user_id} .                                                [ 80%]
+PATCH /api/users/{user_id} .                                              [100%]
+
+=================================== SUMMARY ====================================
+
+Performed checks:
+    not_a_server_error                    5 / 5 passed          PASSED 
+
+Tip: Use the `--report` CLI option to visualize test results via Schemathesis.io.
+We run additional conformance checks on reports from public repos.
+
+============================== 5 passed in 1.00s ===============================

test/cli/test_commands.py

@@ -1507,6 +1507,91 @@ def test_openapi_links_disabled(cli, schema_url, hypothesis_max_examples, snapsh
     )
 
 
+@pytest.mark.openapi_version("3.0")
+@pytest.mark.operations("create_user", "get_user")
+def test_unresolvable_links(cli, empty_open_api_3_schema, testdir, snapshot_cli, base_url):
+    empty_open_api_3_schema["paths"] = {
+        "/users/": {
+            "post": {
+                "requestBody": {
+                    "required": True,
+                    "content": {
+                        "application/json": {
+                            "schema": {
+                                "type": "object",
+                                "properties": {
+                                    "first_name": {"type": "string", "minLength": 3},
+                                    "last_name": {"type": "string", "minLength": 3},
+                                },
+                                "required": ["first_name", "last_name"],
+                                "additionalProperties": False,
+                            }
+                        }
+                    },
+                },
+                "responses": {
+                    "201": {
+                        "description": "OK",
+                        "links": {
+                            "next": {
+                                "operationId": "get_user",
+                                "parameters": {"user_id": "$response.body#/invalid_value"},
+                            },
+                            "update": {
+                                "operationId": "update_user",
+                                "parameters": {"user_id": "$response.body#/id"},
+                                "requestBody": {"first_name": "foo", "last_name": "bar"},
+                            },
+                        },
+                    }
+                },
+            },
+        },
+        "/users/{user_id}": {
+            "parameters": [{"in": "path", "name": "user_id", "required": True, "schema": {"type": "string"}}],
+            "get": {
+                "operationId": "get_user",
+                "responses": {
+                    "200": {
+                        "description": "OK",
+                    }
+                },
+            },
+            "patch": {
+                "operationId": "update_user",
+                "requestBody": {
+                    "content": {
+                        "application/json": {
+                            "schema": {
+                                "type": "object",
+                                "properties": {
+                                    "first_name": {"type": "string", "minLength": 3},
+                                    "last_name": {"type": "string", "minLength": 3},
+                                },
+                                "required": ["first_name", "last_name"],
+                                "additionalProperties": False,
+                            }
+                        }
+                    },
+                    "required": True,
+                },
+                "responses": {"200": {"description": "OK"}, "404": {"description": "Not found"}},
+            },
+        },
+    }
+    schema_file = testdir.make_openapi_schema_file(empty_open_api_3_schema)
+    assert (
+        cli.run(
+            str(schema_file),
+            f"--base-url={base_url}",
+            "--hypothesis-max-examples=1",
+            "--show-trace",
+            "--validate-schema=true",
+        )
+        == snapshot_cli
+    )
+
+
 @pytest.mark.parametrize("recursion_limit", (1, 5))
 @pytest.mark.operations("create_user", "get_user", "update_user")
 @flaky(max_runs=5, min_passes=1)

test/specs/openapi/test_stateful.py

@@ -262,7 +262,7 @@ def test_trimmed_output(testdir, app_schema, base_url):
 @pytest.mark.parametrize("method", ("requests", "werkzeug"))
 @pytest.mark.openapi_version("3.0")
 @pytest.mark.operations("create_user", "get_user", "update_user")
-def test_history(testdir, app_schema, base_url, response_factory, method):
+def test_history(app_schema, response_factory, method):
     # When cases are serialized
     schema = schemathesis.from_dict(app_schema)
     first = schema["/users/"]["POST"].make_case(body={"first_name": "Foo", "last_name": "bar"})