Leaking Abstraction

Implementation details bubbling up through an abstraction.

“All non-trivial abstractions, to some degree, are leaky.” – Joel Spolsky

Signs of Use (Symptoms)

• Users of an abstraction must know about its internals to use it correctly.
• Exceptions or errors from lower layers propagate up unchanged.

Why it is bad (Consequences)

• Abstraction fails: The whole point of abstractions is to hide complexity.
• Coupling: Clients become coupled to the implementation.

Why it happens (Root Cause)

Abstractions are hard. Edge cases expose the underlying reality.

Refactoring Solution

• Strengthen the abstraction: Handle edge cases within it.
• Wrap exceptions: Translate low-level errors to domain errors.

Code example

Typescript

Bad

Good