avoid_collapsible_if

v0.8.0 Warning Fix Control Flow

This rule flags an if statement whose body is nothing but another if, where neither has an else.

Why use this rule

Two nested conditions with no else on either level are a conjunction written across two blocks. Merging them with && states the real condition in one place and removes a level of indentation from everything inside.

The nested form also hides the relationship: a reader has to scan to the end of the outer block to confirm nothing else happens there.

Don’t

if (user != null) {
  if (user.isActive) {
    sendNotification(user);
  }
}

Do

if (user != null && user.isActive) {
  sendNotification(user);
}

Known limitations

The rule stays silent whenever the nesting could carry meaning:

• An else on either level.
• Any other statement in the outer block, before or after the inner if.
• A pattern if (x case P) on either level, which cannot be joined with &&.

The quick fix parenthesises an operand when needed, so merging a condition containing || does not change precedence.

Configuration

This rule is in the recommended preset, so it is on with preset: recommended or preset: opinionated. Add it to preset: core with avoid_collapsible_if: true.

To turn it off:

many_lints.yaml

rules:
  avoid_collapsible_if: false

To keep the rule on but skip certain paths, use per-rule exclude.

Related rules

• avoid_redundant_else — Drop the else when the if branch always exits.
• prefer_early_return — Replace a body-wrapping if with an early-return guard.
• prefer_immediate_return — Return an expression directly instead of via a throwaway variable.
• avoid_cascade_after_if_null — Detect cascades after if-null operators without parentheses.