Clean up Exception structures (#449)

Most exceptions had a messages dictionary that only made sense in
Validation and Data-related exceptions. This PR changes exception
structures to be simpler and to use the messages dictionary only where necessary.

We also subclass Exception and create a new exception class, `ProteanException`
from which all exceptions are subclassed.

The following exceptions were simplified:
- `NoDomainException`
- `ObjectNotFoundError`
- `IncorrectUsageError`

docs/guides/change-state/commands.md

@@ -81,9 +81,6 @@ Out[3]: <PublishArticle: PublishArticle object ({'article_id': '1', 'published_a
 
 In [4]: publish_article_command.published_at = datetime.now() - timedelta(hours=24)
 ...
-IncorrectUsageError: {
-    '_command': [
-        'Command Objects are immutable and cannot be modified once created'
-    ]
+IncorrectUsageError: 'Command Objects are immutable and cannot be modified once created'
 }
 ```

docs/guides/domain-definition/entities.md

@@ -33,7 +33,7 @@ specified while defining the identity, you will see an `IncorrectUsageError`:
 ... class Comment:
 ...     content = String(max_length=500)
 ... 
-IncorrectUsageError: {'_entity': ['Entity `Comment` needs to be associated with an Aggregate']}
+IncorrectUsageError: 'Entity `Comment` needs to be associated with an Aggregate'
 ```
 
 An Entity cannot enclose another Entity (or Aggregate). Trying to do so will
@@ -44,7 +44,7 @@ throw `IncorrectUsageError`.
 ... class SubComment:
 ...     parent = Comment()
 ... 
-IncorrectUsageError: {'_entity': ['Entity `Comment` needs to be associated with an Aggregate']}
+IncorrectUsageError: 'Entity `Comment` needs to be associated with an Aggregate'
 ```
 <!-- FIXME Ensure entities cannot enclose other entities. When entities
 enclose something other than permitted fields, through an error-->

docs/guides/domain-definition/events.md

@@ -195,9 +195,5 @@ In [2]: renamed = UserRenamed(user_id=user.id, name="John Doe Jr.")
 
 In [3]: renamed.name = "John Doe Sr."
 ...
-IncorrectUsageError: {
-    '_message': [
-        'Event/Command Objects are immutable and cannot be modified once created'
-    ]
-}
+IncorrectUsageError: 'Event/Command Objects are immutable and cannot be modified once created'
 ```

docs/guides/domain-definition/value-objects.md

@@ -228,7 +228,7 @@ In [3]: class Balance(BaseValueObject):
    ...:     currency = String(max_length=3, unique=True)
    ...:     amount = Float()
 ...
-IncorrectUsageError: {'_value_object': ["Value Objects cannot contain fields marked 'unique' (field 'currency')"]}
+IncorrectUsageError: "Value Objects cannot contain fields marked 'unique' (field 'currency')"
 ```
 
 Same case if you try to find a Value Object's `id_field`:
@@ -238,7 +238,7 @@ In [4]: from protean.reflection import id_field
 
 In [5]: id_field(Balance)
 ...
-IncorrectUsageError: {"identity": ["<class '__main__.Balance'> does not have identity fields"]}
+IncorrectUsageError: "<class '__main__.Balance'> does not have identity fields"
 ```
 
 ## Immutability
@@ -250,5 +250,5 @@ In [1]: bal1 = Balance(currency='USD', amount=100.0)
 
 In [2]: bal1.currency = "CAD"
 ...
-IncorrectUsageError: {'_value_object': ["Value Objects are immutable and cannot be modified once created"]}
+IncorrectUsageError: "Value Objects are immutable and cannot be modified once created"
 ```

src/protean/adapters/repository/elasticsearch.py

@@ -235,10 +235,8 @@ def _update(self, model_obj: Any):
         except NotFoundError as exc:
             logger.error(f"Database Record not found: {exc}")
             raise ObjectNotFoundError(
-                {
-                    "_entity": f"`{self.entity_cls.__name__}` object with identifier {identifier} "
-                    f"does not exist."
-                }
+                f"`{self.entity_cls.__name__}` object with identifier {identifier} "
+                f"does not exist."
             )
 
         try:

src/protean/adapters/repository/memory.py

@@ -390,10 +390,8 @@ def _update(self, model_obj):
             # Check if object is present
             if identifier not in conn._db["data"][self.schema_name]:
                 raise ObjectNotFoundError(
-                    {
-                        "_entity": f"`{self.__class__.__name__}` object with identifier {identifier} "
-                        f"does not exist."
-                    }
+                    f"`{self.__class__.__name__}` object with identifier {identifier} "
+                    f"does not exist."
                 )
 
             conn._db["data"][self.schema_name][identifier] = model_obj
@@ -434,10 +432,8 @@ def _delete(self, model_obj):
             # Check if object is present
             if identifier not in conn._db["data"][self.schema_name]:
                 raise ObjectNotFoundError(
-                    {
-                        "_entity": f"`{self.entity_cls.__name__}` object with identifier {identifier} "
-                        f"does not exist."
-                    }
+                    f"`{self.entity_cls.__name__}` object with identifier {identifier} "
+                    f"does not exist."
                 )
 
             del conn._db["data"][self.schema_name][identifier]

src/protean/adapters/repository/sqlalchemy.py

@@ -383,10 +383,8 @@ def _update(self, model_obj):
             conn.rollback()
             conn.close()
             raise ObjectNotFoundError(
-                {
-                    "_entity": f"`{self.entity_cls.__name__}` object with identifier {identifier} "
-                    f"does not exist."
-                }
+                f"`{self.entity_cls.__name__}` object with identifier {identifier} "
+                f"does not exist."
             )
 
         # Sync DB Record with current changes. When the session is committed, changes are automatically synced
@@ -447,10 +445,8 @@ def _delete(self, model_obj):
             conn.rollback()
             conn.close()
             raise ObjectNotFoundError(
-                {
-                    "_entity": f"`{self.entity_cls.__name__}` object with identifier {identifier} "
-                    f"does not exist."
-                }
+                f"`{self.entity_cls.__name__}` object with identifier {identifier} "
+                f"does not exist."
             )
 
         try:

src/protean/cli/__init__.py

@@ -152,7 +152,7 @@ def server(
     try:
         domain = derive_domain(domain)
     except NoDomainException as exc:
-        logger.error(f"Error loading Protean domain: {exc.messages}")
+        logger.error(f"Error loading Protean domain: {exc.args[0]}")
         raise typer.Abort()
 
     from protean.server import Engine

src/protean/cli/shell.py

@@ -31,7 +31,7 @@ def shell(
     try:
         domain_instance = derive_domain(domain)
     except NoDomainException as exc:
-        logger.error(f"Error loading Protean domain: {exc.messages}")
+        logger.error(f"Error loading Protean domain: {exc.args[0]}")
         raise typer.Abort()
 
     if traverse:

src/protean/core/aggregate.py

@@ -257,11 +257,7 @@ def apply(fn):
 
     if len(typing.get_type_hints(fn)) > 2:
         raise IncorrectUsageError(
-            {
-                "_entity": [
-                    f"Handler method `{fn.__name__}` has incorrect number of arguments"
-                ]
-            }
+            f"Handler method `{fn.__name__}` has incorrect number of arguments"
         )
 
     try:
@@ -276,11 +272,7 @@ def apply(fn):
         )
     except StopIteration:
         raise IncorrectUsageError(
-            {
-                "_entity": [
-                    f"Apply method `{fn.__name__}` should accept an argument annotated with the Event class"
-                ]
-            }
+            f"Apply method `{fn.__name__}` should accept an argument annotated with the Event class"
         )
 
     @functools.wraps(fn)

src/protean/core/command.py

@@ -59,11 +59,7 @@ def command_factory(element_cls, domain, **opts):
 
     if not element_cls.meta_.part_of and not element_cls.meta_.abstract:
         raise IncorrectUsageError(
-            {
-                "_command": [
-                    f"Command `{element_cls.__name__}` needs to be associated with an aggregate or a stream"
-                ]
-            }
+            f"Command `{element_cls.__name__}` needs to be associated with an aggregate or a stream"
         )
 
     return element_cls

src/protean/core/command_handler.py

@@ -28,11 +28,7 @@ def command_handler_factory(element_cls, domain, **opts):
 
     if not element_cls.meta_.part_of:
         raise IncorrectUsageError(
-            {
-                "_entity": [
-                    f"Command Handler `{element_cls.__name__}` needs to be associated with an Aggregate"
-                ]
-            }
+            f"Command Handler `{element_cls.__name__}` needs to be associated with an Aggregate"
         )
 
     return element_cls

src/protean/core/domain_service.py

@@ -114,11 +114,7 @@ def domain_service_factory(element_cls, domain, **opts):
 
     if not element_cls.meta_.part_of or len(element_cls.meta_.part_of) < 2:
         raise IncorrectUsageError(
-            {
-                "_entity": [
-                    f"Domain Service `{element_cls.__name__}` needs to be associated with two or more Aggregates"
-                ]
-            }
+            f"Domain Service `{element_cls.__name__}` needs to be associated with two or more Aggregates"
         )
 
     # Iterate through methods marked as `@invariant` and record them for later use

src/protean/core/entity.py

@@ -621,11 +621,7 @@ def entity_factory(element_cls, domain, **opts):
 
     if not element_cls.meta_.part_of:
         raise IncorrectUsageError(
-            {
-                "_entity": [
-                    f"Entity `{element_cls.__name__}` needs to be associated with an Aggregate"
-                ]
-            }
+            f"Entity `{element_cls.__name__}` needs to be associated with an Aggregate"
         )
 
     # Set up reference fields

src/protean/core/event.py

@@ -58,11 +58,7 @@ def domain_event_factory(element_cls, domain, **opts):
 
     if not element_cls.meta_.part_of and not element_cls.meta_.abstract:
         raise IncorrectUsageError(
-            {
-                "_event": [
-                    f"Event `{element_cls.__name__}` needs to be associated with an aggregate or a stream"
-                ]
-            }
+            f"Event `{element_cls.__name__}` needs to be associated with an aggregate or a stream"
         )
 
     return element_cls

src/protean/core/event_handler.py

@@ -36,11 +36,7 @@ def event_handler_factory(element_cls, domain, **opts):
 
     if not (element_cls.meta_.part_of or element_cls.meta_.stream_category):
         raise IncorrectUsageError(
-            {
-                "_entity": [
-                    f"Event Handler `{element_cls.__name__}` needs to be associated with an aggregate or a stream"
-                ]
-            }
+            f"Event Handler `{element_cls.__name__}` needs to be associated with an aggregate or a stream"
         )
 
     return element_cls

src/protean/core/event_sourced_repository.py

@@ -33,9 +33,7 @@ def __init__(self, domain) -> None:
 
     def add(self, aggregate: BaseAggregate) -> None:
         if aggregate is None:
-            raise IncorrectUsageError(
-                {"_entity": ["Aggregate object to persist is invalid"]}
-            )
+            raise IncorrectUsageError("Aggregate object to persist is invalid")
 
         # Proceed only if aggregate has events
         if len(aggregate._events) > 0:
@@ -91,10 +89,8 @@ def get(self, identifier: Identifier) -> BaseAggregate:
 
         if not aggregate:
             raise ObjectNotFoundError(
-                {
-                    "_entity": f"`{self.meta_.part_of.__name__}` object with identifier {identifier} "
-                    f"does not exist."
-                }
+                f"`{self.meta_.part_of.__name__}` object with identifier {identifier} "
+                f"does not exist."
             )
 
         aggregate._event_position = aggregate._version
@@ -107,20 +103,12 @@ def event_sourced_repository_factory(element_cls, domain, **opts):
 
     if not element_cls.meta_.part_of:
         raise IncorrectUsageError(
-            {
-                "_entity": [
-                    f"Repository `{element_cls.__name__}` should be associated with an Aggregate"
-                ]
-            }
+            f"Repository `{element_cls.__name__}` should be associated with an Aggregate"
         )
 
     if not element_cls.meta_.part_of.meta_.is_event_sourced:
         raise IncorrectUsageError(
-            {
-                "_entity": [
-                    f"Repository `{element_cls.__name__}` can only be associated with an Event Sourced Aggregate"
-                ]
-            }
+            f"Repository `{element_cls.__name__}` can only be associated with an Event Sourced Aggregate"
         )
 
     return element_cls

src/protean/core/model.py

@@ -41,11 +41,7 @@ def model_factory(element_cls, domain, **opts):
 
     if not element_cls.meta_.part_of:
         raise IncorrectUsageError(
-            {
-                "_entity": [
-                    f"Model `{element_cls.__name__}` should be associated with an Entity or Aggregate"
-                ]
-            }
+            f"Model `{element_cls.__name__}` should be associated with an Entity or Aggregate"
         )
 
     return element_cls

src/protean/core/repository.py

@@ -266,11 +266,7 @@ def repository_factory(element_cls, domain, **opts):
 
     if not element_cls.meta_.part_of:
         raise IncorrectUsageError(
-            {
-                "_entity": [
-                    f"Repository `{element_cls.__name__}` should be associated with an Aggregate"
-                ]
-            }
+            f"Repository `{element_cls.__name__}` should be associated with an Aggregate"
         )
 
     # FIXME Uncomment
@@ -284,11 +280,7 @@ def repository_factory(element_cls, domain, **opts):
         database.value for database in Database
     ]:
         raise IncorrectUsageError(
-            {
-                "_entity": [
-                    f"Repository `{element_cls.__name__}` should be associated with a valid Database"
-                ]
-            }
+            f"Repository `{element_cls.__name__}` should be associated with a valid Database"
         )
 
     return element_cls

src/protean/core/subscriber.py

@@ -39,20 +39,12 @@ def subscriber_factory(element_cls, domain, **opts):
 
     if not element_cls.meta_.event:
         raise IncorrectUsageError(
-            {
-                "_entity": [
-                    f"Subscriber `{element_cls.__name__}` needs to be associated with an Event"
-                ]
-            }
+            f"Subscriber `{element_cls.__name__}` needs to be associated with an Event"
         )
 
     if not element_cls.meta_.broker:
         raise IncorrectUsageError(
-            {
-                "_entity": [
-                    f"Subscriber `{element_cls.__name__}` needs to be associated with a Broker"
-                ]
-            }
+            f"Subscriber `{element_cls.__name__}` needs to be associated with a Broker"
         )
 
     return element_cls