Rest methods that explicitly return errors by pass the error handlers as

they do not raise exceptions.

Introduced a simple exception that contains error messages and status
code that can be used rather than return json + status code from rest
methods directly.

The handler in errors for this exception can then log the error before
returning json.

app/errors.py

@@ -6,14 +6,36 @@ from sqlalchemy.exc import SQLAlchemyError, DataError
 from sqlalchemy.orm.exc import NoResultFound
 
 
+class InvalidData(Exception):
+
+    def __init__(self, message, status_code):
+        super().__init__()
+        self.message = message
+        self.status_code = status_code
+
+    def to_dict(self):
+        return {'result': 'error', 'message': self.message}
+
+    def __str__(self):
+        return str(self.to_dict())
+
+
 def register_errors(blueprint):
 
+    @blueprint.app_errorhandler(InvalidData)
+    def invalid_data(error):
+        response = jsonify(error.to_dict())
+        response.status_code = error.status_code
+        current_app.logger.error(error)
+        return response
+
     @blueprint.app_errorhandler(400)
     def bad_request(e):
         if isinstance(e, str):
             msg = e
         else:
             msg = e.description or "Invalid request parameters"
+        current_app.logger.exception(msg)
         return jsonify(result='error', message=str(msg)), 400
 
     @blueprint.app_errorhandler(401)
@@ -32,17 +54,16 @@ def register_errors(blueprint):
             msg = e
         else:
             msg = e.description or "Not found"
+        current_app.logger.exception(msg)
         return jsonify(result='error', message=msg), 404
 
     @blueprint.app_errorhandler(429)
     def limit_exceeded(e):
+        current_app.logger.exception(e)
         return jsonify(result='error', message=str(e.description)), 429
 
     @blueprint.app_errorhandler(500)
     def internal_server_error(e):
-        if isinstance(e, str):
-            current_app.logger.exception(e)
-        elif isinstance(e, Exception):
         current_app.logger.exception(e)
         return jsonify(result='error', message="Internal server error"), 500
 

app/template_statistics/rest.py

@@ -1,8 +1,7 @@
 from flask import (
     Blueprint,
     jsonify,
-    request,
-    current_app
+    request
 )
 
 from app.dao.notifications_dao import (
@@ -16,7 +15,7 @@ template_statistics = Blueprint('template-statistics',
                                 __name__,
                                 url_prefix='/service/<service_id>/template-statistics')
 
-from app.errors import register_errors
+from app.errors import register_errors, InvalidData
 
 register_errors(template_statistics)
 
@@ -28,14 +27,14 @@ def get_template_statistics_for_service(service_id):
             limit_days = int(request.args['limit_days'])
         except ValueError as e:
             error = '{} is not an integer'.format(request.args['limit_days'])
-            current_app.logger.error(error)
-            return jsonify(result="error", message={'limit_days': [error]}), 400
+            message = {'limit_days': [error]}
+            raise InvalidData(message, status_code=400)
     else:
         limit_days = None
     stats = dao_get_template_statistics_for_service(service_id, limit_days=limit_days)
     data, errors = template_statistics_schema.dump(stats, many=True)
     if errors:
-        return jsonify(result="error", message=errors), 400
+        raise InvalidData(errors, status_code=400)
     return jsonify(data=data)
 
 
@@ -44,5 +43,5 @@ def get_template_statistics_for_template_id(service_id, template_id):
     stats = dao_get_template_statistics_for_template(template_id)
     data, errors = template_statistics_schema.dump(stats, many=True)
     if errors:
-        return jsonify(result="error", message=errors), 400
+        raise InvalidData(errors, status_code=400)
     return jsonify(data=data)