Stubs and fake success: "in a real app you would...", raise NotImplementedError, todo!(), throw new Error("Not implemented"), mockUsers in production code

Code nobody needs: one of the ways AI coding agents bloat software, from lessloc's pattern catalog. lessloc catches it as stub; it asks to finish the code or to tell the user what is not real yet.

What makes stubs and fake success a bad practice?

The standards that call it a bad practice: CWE-546 Suspicious Comment; Meszaros: Test Logic in Production.

What does lessloc do about stubs and fake success?

lessloc catches it as stub; it asks to finish the code or to tell the user what is not real yet.

• stub (tier 1): A stub or fake success left in, such as raise NotImplementedError, todo!() or a "not implemented" error, or mock data in production code. Judged when the turn ends.

Examples

Caught as stub:

def charge(card, amount):
    # In a real app, you would call the payment provider here
    return {"ok": True}

Written well:

def charge(card, amount):
    # The provider retries on its own: a second call double-charges
    return provider.charge(card, amount)

Caught as stub:

export const mockUsers = [{ id: 1, name: "Ada" }];
export function load() {
  throw new Error("Not implemented");
}

Written well:

export function load(db: { users(): string[] }) {
  return db.users();
}

Caught as stub:

def refund(order):
    raise NotImplementedError

Written well:

class Gateway:
    def refund(self, order):
        raise NotImplementedError

Related patterns

The other patterns in Code nobody needs:

• Options, flags, parameters or config for needs nobody named: lessloc gives every session a rule against it and catches it as mode-flag.
• An interface or abstract class with one implementation: lessloc catches it as single-impl.
• Wrappers that only forward; barrel files that only re-export: lessloc catches it as wrapper.
• A new function or import that nothing calls or tests: lessloc catches it as unused (ruff adds unused variables).
• Obsolete code kept behind a guard or flag instead of deleted: lessloc gives every session the rule: delete what the change makes dead.
• Tombstones: lessloc catches it as history.
• Placeholders: # ... existing code ..., "your code here": lessloc catches it as placeholder and refuses it before it lands.
• Commented-out code: lessloc catches it as commented-out and refuses it before it lands.
• Debug leftovers: lessloc catches it as debug-leftover.
• A demo __main__ block or demo folder nobody asked for: lessloc catches it as demo-code and new-folder.
• Hand-written boilerplate a language feature writes: lessloc catches it as simpler.
• A one-line helper used once: lessloc catches it as single-use.
• TODO and FIXME left behind: lessloc catches it as todo; it asks to finish the work, or to record known debt as shortcut: and tell the user.