Purpose¶

Functions that return bool are easier to read at call sites when their names read as a question. This rule enforces that any function or method with a bool return type annotation starts with is_, has_, or should_.

Configuration¶

rules:
  - name: bool-method-prefix
    type: function
    filter: { return_type: bool }
    naming: { prefix: [is_, has_, should_] }

apply:
  - name: all
    rules: [bool-method-prefix]
    modules: "**"

Violation Example¶

# src/domain/service.py

class SubscriptionService:
    def validate(self) -> bool:   # missing required prefix
        return self._status == "active"

Passing Example¶

# src/domain/service.py

class SubscriptionService:
    def is_valid(self) -> bool:
        return self._status == "active"

Output¶

$ pnl check
src/domain/service.py:4
    [bool-method-prefix] validate (expected prefix: is_ | has_ | should_)

Found 1 violation(s).