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global-state-dependency

Category: Dependency Injection
Severity: Error
Triggered by: pyscn analyze, pyscn check --select di

What it does

Flags a class method that uses a global statement to read or mutate module-level state.

Why is this a problem?

A global inside a method ties the class to a specific module variable that isn't visible from the class's interface. Nothing in OrderService(...) tells a reader that constructing it is not enough — some module-level value must also be primed, or the method will behave unexpectedly.

Tests suffer the most. To exercise a method that touches global state, each test has to reach into the module, save the old value, install a new one, and restore it on teardown — and any test that forgets to clean up leaks state into the next one. Running tests in parallel becomes unsafe.

The dependency is real; it's just hidden. Making it an explicit constructor parameter removes the surprise.

Example

_current_user = None

class AuditLog:
    def record(self, action):
        global _current_user
        entry = {"user": _current_user, "action": action}
        db.insert("audit", entry)

Use instead

Pass the value in through __init__ so the dependency is visible and swappable.

class AuditLog:
    def __init__(self, user):
        self.user = user

    def record(self, action):
        db.insert("audit", {"user": self.user, "action": action})

Options

Option Default Description
di.enabled false Must be true for analyze to run DI rules.
di.min_severity "warning" This rule reports at error; it is surfaced unless min_severity is raised above error.

References