Improve typing in the module

Fixes pallets-eco#65

- make it pass mypy tests (i.e., improve type hinting)
- add mypy test to CI
- add py.typed to setup so that other packages recognize it's typed
- enable async view function decoration (via ensure_sync() as noted on
  https://flask.palletsprojects.com/en/latest/async-await/#extensions)

Signed-off-by: Marek Pikuła <[email protected]>

Author: MarekPikula

Diff for: .github/workflows/tests.yml

@@ -3,6 +3,26 @@ name: Tests
 on: [push, pull_request]
 
 jobs:
+  mypy:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+
+    steps:
+    - uses: actions/checkout@v1
+    - name: Set up Python 3.7
+      uses: actions/setup-python@v1
+      with:
+        python-version: "3.7"
+    - name: Install dependencies
+      if: steps.cache-pip.outputs.cache-hit != 'true'
+      run: |
+        python -m pip install --upgrade pip
+        pip install -r requirements/test.pip
+    - name: Run mypy satic check
+      run: |
+        python3 -m mypy flask_pydantic/
+
   build:
     runs-on: ${{ matrix.os }}
     strategy:

Diff for: flask_pydantic/converters.py

@@ -1,12 +1,12 @@
-from typing import Type
+from typing import Dict, List, Type, Union
 
 from pydantic import BaseModel
-from werkzeug.datastructures import ImmutableMultiDict
+from werkzeug.datastructures import MultiDict
 
 
 def convert_query_params(
-    query_params: ImmutableMultiDict, model: Type[BaseModel]
-) -> dict:
+    query_params: MultiDict[str, str], model: Type[BaseModel]
+) -> Dict[str, Union[str, List[str]]]:
     """
     group query parameters into lists if model defines them
 

Diff for: flask_pydantic/core.py

@@ -1,7 +1,28 @@
+from collections.abc import Iterable
 from functools import wraps
-from typing import Any, Callable, Iterable, List, Optional, Tuple, Type, Union
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    Awaitable,
+    Callable,
+    Dict,
+    List,
+    Optional,
+    Tuple,
+    Type,
+    Union,
+)
+
+from flask import Response, current_app, jsonify, request
+from flask.typing import ResponseReturnValue, RouteCallable
+
+try:
+    from flask_restful import (  # type: ignore
+        original_flask_make_response as make_response,
+    )
+except ImportError:
+    from flask import make_response
 
-from flask import Response, current_app, jsonify, make_response, request
 from pydantic import BaseModel, ValidationError
 from pydantic.tools import parse_obj_as
 
@@ -13,22 +34,33 @@
 )
 from .exceptions import ValidationError as FailedValidation
 
-try:
-    from flask_restful import original_flask_make_response as make_response
-except ImportError:
-    pass
+if TYPE_CHECKING:
+    from pydantic.error_wrappers import ErrorDict
+
+
+ModelResponseReturnValue = Union[ResponseReturnValue, BaseModel]
+ModelRouteCallable = Union[
+    Callable[..., ModelResponseReturnValue],
+    Callable[..., Awaitable[ModelResponseReturnValue]],
+]
 
 
 def make_json_response(
     content: Union[BaseModel, Iterable[BaseModel]],
     status_code: int,
     by_alias: bool,
     exclude_none: bool = False,
-    many: bool = False,
 ) -> Response:
     """serializes model, creates JSON response with given status code"""
-    if many:
-        js = f"[{', '.join([model.json(exclude_none=exclude_none, by_alias=by_alias) for model in content])}]"
+    if not isinstance(content, BaseModel):
+        js = "["
+        js += ", ".join(
+            [
+                model.json(exclude_none=exclude_none, by_alias=by_alias)
+                for model in content
+            ]
+        )
+        js += "]"
     else:
         js = content.json(exclude_none=exclude_none, by_alias=by_alias)
     response = make_response(js, status_code)
@@ -56,9 +88,9 @@ def validate_many_models(model: Type[BaseModel], content: Any) -> List[BaseModel
         return [model(**fields) for fields in content]
     except TypeError:
         # iteration through `content` fails
-        err = [
+        err: List["ErrorDict"] = [
             {
-                "loc": ["root"],
+                "loc": ("root",),
                 "msg": "is not an array of objects",
                 "type": "type_error.array",
             }
@@ -68,30 +100,53 @@ def validate_many_models(model: Type[BaseModel], content: Any) -> List[BaseModel
         raise ManyModelValidationError(ve.errors())
 
 
-def validate_path_params(func: Callable, kwargs: dict) -> Tuple[dict, list]:
-    errors = []
+def validate_path_params(
+    func: ModelRouteCallable, kwargs: Dict[str, Any]
+) -> Tuple[Dict[str, Any], List["ErrorDict"]]:
+    errors: List["ErrorDict"] = []
     validated = {}
     for name, type_ in func.__annotations__.items():
         if name in {"query", "body", "form", "return"}:
             continue
         try:
             value = parse_obj_as(type_, kwargs.get(name))
             validated[name] = value
-        except ValidationError as e:
-            err = e.errors()[0]
-            err["loc"] = [name]
+        except ValidationError as error:
+            err = error.errors()[0]
+            err["loc"] = (name,)
             errors.append(err)
     kwargs = {**kwargs, **validated}
     return kwargs, errors
 
 
-def get_body_dict(**params):
-    data = request.get_json(**params)
+def get_body_dict(**params: Dict[str, Any]) -> Any:
+    data = request.get_json(**params)  # type: ignore
     if data is None and params.get("silent"):
         return {}
     return data
 
 
+def _ensure_model_kwarg(
+    kwarg_name: str,
+    from_validate: Optional[Type[BaseModel]],
+    func: ModelRouteCallable,
+) -> Tuple[Optional[Type[BaseModel]], bool]:
+    """Get model information either from wrapped function or validate kwargs."""
+    in_func_kwargs = func.__annotations__.get(kwarg_name)
+    if in_func_kwargs is None:
+        return from_validate, False
+    assert isinstance(in_func_kwargs, type) and issubclass(
+        in_func_kwargs, BaseModel
+    ), "Model in function arguments needs to be a BaseModel."
+
+    # Ensure that the most "detailed" model is used.
+    if from_validate is None:
+        return in_func_kwargs, True
+    if issubclass(in_func_kwargs, from_validate):
+        return in_func_kwargs, True
+    return from_validate, True
+
+
 def validate(
     body: Optional[Type[BaseModel]] = None,
     query: Optional[Type[BaseModel]] = None,
@@ -100,7 +155,7 @@ def validate(
     response_many: bool = False,
     request_body_many: bool = False,
     response_by_alias: bool = False,
-    get_json_params: Optional[dict] = None,
+    get_json_params: Optional[Dict[str, Any]] = None,
     form: Optional[Type[BaseModel]] = None,
 ):
     """
@@ -163,105 +218,93 @@ def test_route_kwargs(query:Query, body:Body, form:Form):
     -> that will render JSON response with serialized MyModel instance
     """
 
-    def decorate(func: Callable) -> Callable:
+    def decorate(func: ModelRouteCallable) -> RouteCallable:
         @wraps(func)
-        def wrapper(*args, **kwargs):
-            q, b, f, err = None, None, None, {}
-            kwargs, path_err = validate_path_params(func, kwargs)
-            if path_err:
-                err["path_params"] = path_err
-            query_in_kwargs = func.__annotations__.get("query")
-            query_model = query_in_kwargs or query
-            if query_model:
+        def wrapper(*args: Any, **kwargs: Dict[str, Any]) -> ResponseReturnValue:
+            q, b, f, err = None, None, None, FailedValidation()
+            func_kwargs, path_err = validate_path_params(func, kwargs)
+            if len(path_err) > 0:
+                err.path_params = path_err
+            query_model, query_in_kwargs = _ensure_model_kwarg("query", query, func)
+            if query_model is not None:
                 query_params = convert_query_params(request.args, query_model)
                 try:
                     q = query_model(**query_params)
                 except ValidationError as ve:
-                    err["query_params"] = ve.errors()
-            body_in_kwargs = func.__annotations__.get("body")
-            body_model = body_in_kwargs or body
-            if body_model:
+                    err.query_params = ve.errors()
+            body_model, body_in_kwargs = _ensure_model_kwarg("body", body, func)
+            if body_model is not None:
                 body_params = get_body_dict(**(get_json_params or {}))
-                if "__root__" in body_model.__fields__:
-                    try:
-                        b = body_model(__root__=body_params).__root__
-                    except ValidationError as ve:
-                        err["body_params"] = ve.errors()
-                elif request_body_many:
-                    try:
+                try:
+                    if "__root__" in body_model.__fields__:
+                        b = body_model(__root__=body_params).__root__  # type: ignore
+                    elif request_body_many:
                         b = validate_many_models(body_model, body_params)
-                    except ManyModelValidationError as e:
-                        err["body_params"] = e.errors()
-                else:
-                    try:
+                    else:
                         b = body_model(**body_params)
-                    except TypeError:
-                        content_type = request.headers.get("Content-Type", "").lower()
-                        media_type = content_type.split(";")[0]
-                        if media_type != "application/json":
-                            return unsupported_media_type_response(content_type)
-                        else:
-                            raise JsonBodyParsingError()
-                    except ValidationError as ve:
-                        err["body_params"] = ve.errors()
-            form_in_kwargs = func.__annotations__.get("form")
-            form_model = form_in_kwargs or form
-            if form_model:
+                except (ValidationError, ManyModelValidationError) as error:
+                    err.body_params = error.errors()
+                except TypeError as error:
+                    content_type = request.headers.get("Content-Type", "").lower()
+                    media_type = content_type.split(";")[0]
+                    if media_type != "application/json":
+                        return unsupported_media_type_response(content_type)
+                    else:
+                        raise JsonBodyParsingError() from error
+            form_model, form_in_kwargs = _ensure_model_kwarg("form", form, func)
+            if form_model is not None:
                 form_params = request.form
-                if "__root__" in form_model.__fields__:
-                    try:
-                        f = form_model(__root__=form_params).__root__
-                    except ValidationError as ve:
-                        err["form_params"] = ve.errors()
-                else:
-                    try:
+                try:
+                    if "__root__" in form_model.__fields__:
+                        f = form_model(__root__=form_params).__root__  # type: ignore
+                    else:
                         f = form_model(**form_params)
-                    except TypeError:
-                        content_type = request.headers.get("Content-Type", "").lower()
-                        media_type = content_type.split(";")[0]
-                        if media_type != "multipart/form-data":
-                            return unsupported_media_type_response(content_type)
-                        else:
-                            raise JsonBodyParsingError
-                    except ValidationError as ve:
-                        err["form_params"] = ve.errors()
-            request.query_params = q
-            request.body_params = b
-            request.form_params = f
+                except TypeError as error:
+                    content_type = request.headers.get("Content-Type", "").lower()
+                    media_type = content_type.split(";")[0]
+                    if media_type != "multipart/form-data":
+                        return unsupported_media_type_response(content_type)
+                    else:
+                        raise JsonBodyParsingError() from error
+                except ValidationError as ve:
+                    err.form_params = ve.errors()
+            request.query_params = q  # type: ignore
+            request.body_params = b  # type: ignore
+            request.form_params = f  # type: ignore
             if query_in_kwargs:
-                kwargs["query"] = q
+                func_kwargs["query"] = q
             if body_in_kwargs:
-                kwargs["body"] = b
+                func_kwargs["body"] = b
             if form_in_kwargs:
-                kwargs["form"] = f
+                func_kwargs["form"] = f
 
-            if err:
+            if err.check():
                 if current_app.config.get(
                     "FLASK_PYDANTIC_VALIDATION_ERROR_RAISE", False
                 ):
-                    raise FailedValidation(**err)
+                    raise err
                 else:
                     status_code = current_app.config.get(
                         "FLASK_PYDANTIC_VALIDATION_ERROR_STATUS_CODE", 400
                     )
                     return make_response(
-                        jsonify({"validation_error": err}),
-                        status_code
+                        jsonify({"validation_error": err.to_dict()}), status_code
                     )
-            res = func(*args, **kwargs)
+            res: ModelResponseReturnValue = current_app.ensure_sync(func)(
+                *args, **func_kwargs
+            )
 
             if response_many:
-                if is_iterable_of_models(res):
-                    return make_json_response(
-                        res,
-                        on_success_status,
-                        by_alias=response_by_alias,
-                        exclude_none=exclude_none,
-                        many=True,
-                    )
-                else:
+                if not is_iterable_of_models(res):
                     raise InvalidIterableOfModelsException(res)
 
+                return make_json_response(
+                    res,  # type: ignore  # Iterability and type is ensured above.
+                    on_success_status,
+                    by_alias=response_by_alias,
+                    exclude_none=exclude_none,
+                )
+
             if isinstance(res, BaseModel):
                 return make_json_response(
                     res,
@@ -275,23 +318,29 @@ def wrapper(*args, **kwargs):
                 and len(res) in [2, 3]
                 and isinstance(res[0], BaseModel)
             ):
-                headers = None
+                headers: Optional[
+                    Union[Dict[str, Any], Tuple[Any, ...], List[Any]]
+                ] = None
                 status = on_success_status
                 if isinstance(res[1], (dict, tuple, list)):
                     headers = res[1]
-                elif len(res) == 3 and isinstance(res[2], (dict, tuple, list)):
-                    status = res[1]
-                    headers = res[2]
-                else:
+                elif isinstance(res[1], int):
                     status = res[1]
 
+                # Following type ignores should be fixed once
+                # https://github.com/python/mypy/issues/1178 is fixed.
+                if len(res) == 3 and isinstance(
+                    res[2], (dict, tuple, list)  # type: ignore[misc]
+                ):
+                    headers = res[2]  # type: ignore[misc]
+
                 ret = make_json_response(
                     res[0],
                     status,
                     exclude_none=exclude_none,
                     by_alias=response_by_alias,
                 )
-                if headers:
+                if headers is not None:
                     ret.headers.update(headers)
                 return ret