Add specific exceptions for missing id & unfetched links

src/api/categories.py

@@ -11,6 +11,7 @@ from src.api.auth.dependencies import LoggedInDep
 from src.db.models.category import Category
 from src.db.models.event import Event
 from src.db.models.user import User
+from src.utils.db import MissingIdError
 from src.utils.logging import get_logger
 
 from .auth import CurrentUserDep
@@ -49,7 +50,7 @@ class CategoryData(_BaseCategoryData):
     def from_category(cls, category: Category) -> "CategoryData":
         """Construct CategoryData from an instance of Category."""
         if category.id is None:
-            raise ValueError("Got a category without id")
+            raise MissingIdError(category)
 
         return cls(
             name=category.name,

src/api/sessions.py

@@ -7,6 +7,7 @@ from pydantic import BaseModel
 
 from src.api.auth.jwt import invalidate_access_tokens
 from src.db.models.token import Token
+from src.utils.db import MissingIdError, UnfetchedLinkError
 from src.utils.logging import get_logger
 
 from .auth import AnyTokenDep, CurrentUserDep
@@ -36,15 +37,15 @@ class UserSession(BaseModel):
         # This can only happen if the attendee wasn't yet committed to the db,
         # within the context of this function, that should never happen.
         if token.id is None:
-            raise ValueError("Got token without id")
+            raise MissingIdError(token)
 
         if token.parent_token:
             # This function expects the parent token links to be fetched already
             if isinstance(token.parent_token, Link):
-                raise TypeError("Parent token must be fetched before calling this function")
+                raise UnfetchedLinkError(token.parent_token)
 
             if token.parent_token.id is None:
-                raise ValueError("Got parent token without id")
+                raise MissingIdError(token.parent_token)
 
         return cls(
             id=str(token.id),

src/api/users.py

@@ -10,6 +10,7 @@ from src.api.auth.dependencies import LoggedInDep
 from src.api.auth.passwords import check_hashed_password, create_password_hash
 from src.db.models.token import Token
 from src.db.models.user import User
+from src.utils.db import MissingIdError
 from src.utils.logging import get_logger
 
 from .auth import CurrentUserDep
@@ -50,7 +51,7 @@ class UserData(BaseModel):
     def from_user(cls, user: User) -> "UserData":
         """Construct UserData from a User instance."""
         if user.id is None:
-            raise ValueError("Got a user without id")
+            raise MissingIdError(user)
 
         return cls(
             user_id=user.id,

src/utils/db.py

@@ -0,0 +1,27 @@
+from typing import final
+
+from beanie import Document, Link
+
+
+@final
+class MissingIdError(ValueError):
+    """Raised when an item is missing an id.
+
+    This usually happens with objects that were not yet committed to the db.
+    """
+
+    def __init__(self, item: Document):
+        self.item = item
+        super().__init__(f"Item {item} is missing an id")
+
+
+@final
+class UnfetchedLinkError[T](ValueError):
+    """Raised when a link object is found, where a document was expected.
+
+    This usually happens when an object is fetched from the db without link fetching enabled.
+    """
+
+    def __init__(self, link: Link[T]):
+        self.link = link
+        super().__init__(f"Link {link} was not fetched")