Generate examples with jsf (#1891)

Fixes https://github.com/spec-first/connexion/issues/1719 .

Builds on work of https://github.com/spec-first/connexion/pull/1718,
pulling in external library to provide the fake data from JSON schema.

Changes proposed in this pull request:

* Use JSF library to generate sample data for mocking APIs without
examples.
* Add this as a new extra dependency "mock"

See discussion on https://github.com/spec-first/connexion/pull/1870

---------

Co-authored-by: Robbe Sneyders <robbe.sneyders@gmail.com>

connexion/mock.py

@@ -51,4 +51,9 @@ class MockResolver(Resolver):
         resp, code = operation.example_response()
         if resp is not None:
             return resp, code
-        return "No example response was defined.", code
+        return (
+            "No example response defined in the API, and response "
+            "auto-generation disabled. To enable response auto-generation, "
+            "install connexion using the mock extra (connexion[mock])",
+            501,
+        )

connexion/operations/openapi.py

@@ -7,7 +7,7 @@ import logging
 from connexion.datastructures import MediaTypeDict
 from connexion.operations.abstract import AbstractOperation
 from connexion.uri_parsing import OpenAPIURIParser
-from connexion.utils import deep_get
+from connexion.utils import build_example_from_schema, deep_get
 
 logger = logging.getLogger("connexion.operations.openapi3")
 
@@ -187,31 +187,11 @@ class OpenAPIOperation(AbstractOperation):
             pass
 
         try:
-            return (
-                self._nested_example(deep_get(self._responses, schema_path)),
-                status_code,
-            )
+            schema = deep_get(self._responses, schema_path)
         except KeyError:
-            return (None, status_code)
+            return ("No example response or response schema defined.", status_code)
 
-    def _nested_example(self, schema):
-        try:
-            return schema["example"]
-        except KeyError:
-            pass
-        try:
-            # Recurse if schema is an object
-            return {
-                key: self._nested_example(value)
-                for (key, value) in schema["properties"].items()
-            }
-        except KeyError:
-            pass
-        try:
-            # Recurse if schema is an array
-            return [self._nested_example(schema["items"])]
-        except KeyError:
-            raise
+        return (build_example_from_schema(schema), status_code)
 
     def get_path_parameter_types(self):
         types = {}

connexion/operations/swagger2.py

@@ -8,7 +8,7 @@ import typing as t
 from connexion.exceptions import InvalidSpecification
 from connexion.operations.abstract import AbstractOperation
 from connexion.uri_parsing import Swagger2URIParser
-from connexion.utils import deep_get
+from connexion.utils import build_example_from_schema, deep_get
 
 logger = logging.getLogger("connexion.operations.swagger2")
 
@@ -209,31 +209,11 @@ class Swagger2Operation(AbstractOperation):
             pass
 
         try:
-            return (
-                self._nested_example(deep_get(self._responses, schema_path)),
-                status_code,
-            )
+            schema = deep_get(self._responses, schema_path)
         except KeyError:
-            return (None, status_code)
+            return ("No example response or response schema defined.", status_code)
 
-    def _nested_example(self, schema):
-        try:
-            return schema["example"]
-        except KeyError:
-            pass
-        try:
-            # Recurse if schema is an object
-            return {
-                key: self._nested_example(value)
-                for (key, value) in schema["properties"].items()
-            }
-        except KeyError:
-            pass
-        try:
-            # Recurse if schema is an array
-            return [self._nested_example(schema["items"])]
-        except KeyError:
-            raise
+        return (build_example_from_schema(schema), status_code)
 
     def body_name(self, content_type: str = None) -> str:
         return self.body_definition(content_type).get("name", "body")

connexion/utils.py

@@ -512,3 +512,35 @@ def sort_apis_by_basepath(apis: t.List["API"]) -> t.List["API"]:
     :return: List of APIs sorted by basepath
     """
     return sort_routes(apis, key=lambda api: api.base_path or "/")
+
+
+def build_example_from_schema(schema):
+    if "example" in schema:
+        return schema["example"]
+
+    if "properties" in schema:
+        # Recurse if schema is an object
+        return {
+            key: build_example_from_schema(value)
+            for (key, value) in schema["properties"].items()
+        }
+
+    if "items" in schema:
+        # Recurse if schema is an array
+        min_item_count = schema.get("minItems", 0)
+        max_item_count = schema.get("maxItems")
+
+        if max_item_count is None or max_item_count >= min_item_count + 1:
+            item_count = min_item_count + 1
+        else:
+            item_count = min_item_count
+
+        return [build_example_from_schema(schema["items"]) for n in range(item_count)]
+
+    try:
+        from jsf import JSF
+    except ImportError:
+        return None
+
+    faker = JSF(schema)
+    return faker.generate()

docs/cli.rst

@@ -47,7 +47,10 @@ Running a mock server
 ---------------------
 
 You can run a simple server which returns example responses on every request.
-The example responses must be defined in the ``examples`` response property of the OpenAPI specification.
+
+The example responses can be defined in the ``examples`` response property of
+the OpenAPI specification. If no examples are specified, and you have installed connexion with the `mock` extra (`pip install connexion[mock]`), an example is generated based on the provided schema.
+
 Your API specification file is not required to have any ``operationId``.
 
 .. code-block:: bash

pyproject.toml

@@ -48,24 +48,26 @@ python = '^3.8'
 asgiref = ">= 3.4"
 httpx = ">= 0.23"
 inflection = ">= 0.3.1"
-jsonschema = ">= 4.0.1"
+jsonschema = ">=4.17.3"
 Jinja2 = ">= 3.0.0"
 python-multipart = ">= 0.0.5"
 PyYAML = ">= 5.1"
 requests = ">= 2.27"
 starlette = ">= 0.35"
-typing-extensions = ">= 4"
+typing-extensions = ">= 4.6.1"
 werkzeug = ">= 2.2.1"
 
 a2wsgi = { version = ">= 1.7", optional = true }
 flask = { version = ">= 2.2", extras = ["async"], optional = true }
 swagger-ui-bundle = { version = ">= 1.1.0", optional = true }
 uvicorn = { version = ">= 0.17.6", extras = ["standard"], optional = true }
+jsf = { version = ">=0.10.0", optional = true }
 
 [tool.poetry.extras]
 flask = ["a2wsgi", "flask"]
 swagger-ui = ["swagger-ui-bundle"]
 uvicorn = ["uvicorn"]
+mock = ["jsf"]
 
 [tool.poetry.group.tests.dependencies]
 pre-commit = "~2.21.0"

tests/test_mock.py

@@ -224,7 +224,8 @@ def test_mock_resolver_no_example_nested_in_object():
 
     response, status_code = resolver.mock_operation(operation)
     assert status_code == 200
-    assert response == "No example response was defined."
+    assert isinstance(response, dict)
+    assert isinstance(response["foo"], str)
 
 
 def test_mock_resolver_no_example_nested_in_list_openapi():
@@ -256,7 +257,8 @@ def test_mock_resolver_no_example_nested_in_list_openapi():
 
     response, status_code = resolver.mock_operation(operation)
     assert status_code == 202
-    assert response == "No example response was defined."
+    assert isinstance(response, list)
+    assert all(isinstance(c, str) for c in response)
 
 
 def test_mock_resolver_no_examples():
@@ -278,7 +280,7 @@ def test_mock_resolver_no_examples():
 
     response, status_code = resolver.mock_operation(operation)
     assert status_code == 418
-    assert response == "No example response was defined."
+    assert response == "No example response or response schema defined."
 
 
 def test_mock_resolver_notimplemented():
@@ -315,4 +317,7 @@ def test_mock_resolver_notimplemented():
     )
 
     # check if it is using the mock function
-    assert operation._resolution.function() == ("No example response was defined.", 418)
+    assert operation._resolution.function() == (
+        "No example response or response schema defined.",
+        418,
+    )

tests/test_mock2.py

@@ -0,0 +1,162 @@
+from datetime import datetime
+from re import fullmatch
+
+from connexion.utils import build_example_from_schema
+
+
+def test_build_example_from_schema_string():
+    schema = {
+        "type": "string",
+    }
+    example = build_example_from_schema(schema)
+    assert isinstance(example, str)
+
+
+def test_build_example_from_schema_integer():
+    schema = {
+        "type": "integer",
+    }
+    example = build_example_from_schema(schema)
+    assert isinstance(example, int)
+
+
+def test_build_example_from_schema_number():
+    schema = {
+        "type": "number",
+    }
+    example = build_example_from_schema(schema)
+    assert isinstance(example, float)
+
+
+def test_build_example_from_schema_boolean():
+    schema = {
+        "type": "boolean",
+    }
+    example = build_example_from_schema(schema)
+    assert isinstance(example, bool)
+
+
+def test_build_example_from_schema_integer_minimum():
+    schema = {
+        "type": "integer",
+        "minimum": 4,
+    }
+    example = build_example_from_schema(schema)
+    assert example >= schema["minimum"] and isinstance(example, int)
+
+
+def test_build_example_from_schema_integer_maximum():
+    schema = {
+        "type": "integer",
+        "maximum": 17,
+    }
+    example = build_example_from_schema(schema)
+    assert example <= schema["maximum"] and isinstance(example, int)
+
+
+def test_build_example_from_schema_integer_exclusive_minimum():
+    schema = {
+        "type": "integer",
+        "minimum": 4,
+        "exclusiveMinimum": True,
+    }
+    example = build_example_from_schema(schema)
+    assert example > schema["minimum"] and isinstance(example, int)
+
+
+def test_build_example_from_schema_integer_exclusive_maximum():
+    schema = {
+        "type": "integer",
+        "maximum": 17,
+        "exclusiveMaximum": True,
+    }
+    example = build_example_from_schema(schema)
+    assert example < schema["maximum"] and isinstance(example, int)
+
+
+def test_build_example_from_schema_string_regular_expression():
+    pattern = r"^\d{3}-\d{2}-\d{4}$"
+    schema = {
+        "type": "string",
+        "pattern": pattern,
+    }
+    example = build_example_from_schema(schema)
+    assert fullmatch(pattern, example) != None and isinstance(example, str)
+
+
+def test_build_example_from_schema_string_maximum():
+    schema = {
+        "type": "string",
+        "maxLength": 20,
+    }
+    example = build_example_from_schema(schema)
+    assert isinstance(example, str) and len(example) <= schema["maxLength"]
+
+
+def test_build_example_from_schema_string_minimum():
+    schema = {
+        "type": "string",
+        "minLength": 20,
+    }
+    example = build_example_from_schema(schema)
+    assert isinstance(example, str) and len(example) >= schema["minLength"]
+
+
+def test_build_example_from_schema_enum():
+    schema = {"type": "string", "enum": ["asc", "desc"]}
+    example = build_example_from_schema(schema)
+    assert isinstance(example, str)
+    assert example == "asc" or example == "desc"
+
+
+def test_build_example_from_complex_schema():
+    schema = {
+        "type": "object",
+        "properties": {
+            "datetimeField": {"type": "string", "format": "date-time"},
+            "integerField": {
+                "type": "integer",
+                "minimum": 2,
+                "maximum": 5,
+                "exclusiveMinimum": True,
+                "multipleOf": 2,
+            },
+            "arrayOfNumbersField": {
+                "type": "array",
+                "items": {
+                    "type": "number",
+                    "format": "float",
+                    "minimum": 0.1,
+                    "maximum": 0.9,
+                    "multipleOf": 0.1,
+                },
+                "minItems": 3,
+                "maxItems": 5,
+            },
+            "objectField": {
+                "type": "object",
+                "properties": {
+                    "nestedBoolean": {"type": "boolean"},
+                    "stringWithExample": {
+                        "type": "string",
+                        "example": "example-string",
+                    },
+                },
+            },
+        },
+    }
+    example = build_example_from_schema(schema)
+
+    # Check that ValueError is not raised on invalid datetime.
+    datetime.fromisoformat(example["datetimeField"])
+    assert example["integerField"] == 4
+
+    assert isinstance(example["arrayOfNumbersField"], list)
+    assert 3 <= len(example["arrayOfNumbersField"]) <= 5
+    assert all(0.1 <= num <= 0.9 for num in example["arrayOfNumbersField"])
+
+    example_boolean = example["objectField"]["nestedBoolean"]
+    assert example_boolean is True or example_boolean is False
+
+    # Check that if an example is provided then it is used directly.
+    assert example["objectField"]["stringWithExample"] == "example-string"

tests/test_mock3.py

@@ -103,7 +103,7 @@ def test_mock_resolver_no_examples():
 
     response, status_code = resolver.mock_operation(operation)
     assert status_code == 418
-    assert response == "No example response was defined."
+    assert response == "No example response or response schema defined."
 
 
 def test_mock_resolver_notimplemented():
@@ -133,4 +133,7 @@ def test_mock_resolver_notimplemented():
         resolver=resolver,
     )
     # check if it is using the mock function
-    assert operation._resolution.function() == ("No example response was defined.", 418)
+    assert operation._resolution.function() == (
+        "No example response or response schema defined.",
+        418,
+    )