Merge pull request #5920 from hotosm/enhance/5910-validation-error

Refactor request body validation using decorator

backend/models/dtos/__init__.py

@@ -0,0 +1,60 @@
+from functools import wraps
+from flask import request
+from schematics.exceptions import DataError
+
+
+from backend.exceptions import BadRequest
+
+
+def get_validation_errors(e):
+    """Returns a list of validation errors from a schematics DataError"""
+    return [
+        {"field": field, "message": str(error[0])} for field, error in e.errors.items()
+    ]
+
+
+def validate_request(dto_class):
+    """
+    Decorator to validate request against a DTO class.
+    --------------------------------
+    NOTE: This decorator should be applied after the token_auth decorator (if used) so that
+    the authenticated user id can be set on the DTO if the DTO has a user_id field.
+    --------------------------------
+    Parameters:
+        dto_class: DTO
+            The DTO class to validate against
+    """
+
+    def decorator(f):
+        @wraps(f)
+        def wrapper(*args, **kwargs):
+            from backend.services.users.authentication_service import token_auth
+
+            try:
+                dto = dto_class()
+
+                # Set attribute values from request body, query parameters, and path parameters
+                for attr in dto.__class__._fields:
+                    if request.is_json and attr in request.json:
+                        setattr(dto, attr, request.json[attr])
+                    elif attr in request.args:
+                        setattr(dto, attr, request.args.get(attr))
+                    elif attr in kwargs:
+                        setattr(dto, attr, kwargs[attr])
+
+                #  Set authenticated user id if user_id is a field in the DTO
+                if "user_id" in dto.__class__._fields:
+                    dto.user_id = token_auth.current_user()
+
+                dto.validate()
+                request.validated_dto = (
+                    dto  # Set validated DTO on request object for use in view function
+                )
+            except DataError as e:
+                field_errors = get_validation_errors(e)
+                raise BadRequest(field_errors=field_errors)
+            return f(*args, **kwargs)
+
+        return wrapper
+
+    return decorator