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Many Lints

no_equal_conditions

v1.0.0 Warning Control Flow

This rule flags an if/else if chain that tests the same condition twice.

The second test can never be reached: the first branch already took every case it would have matched. Whatever the repeated branch does is dead code, and the case it was meant to handle silently falls through to else — so the bug shows up as a missing behaviour rather than an error.

Don’t

Section titled “Don’t”

A branch duplicated and its body edited while its condition was left alone:

class Status {
  bool get isPending => true;
  bool get isFailed => false;
  bool get isDone => false;
}


void showSpinner() {}
void showRetry() {}
void showResult() {}


void render(Status status) {
  if (status.isPending) {
    showSpinner();
  } else if (status.isPending) {
    showRetry();
  } else if (status.isDone) {
    showResult();
  }
}

showRetry() never runs, and a failed status falls off the end of the chain in silence.

Do

Section titled “Do”
class Status {
  bool get isPending => true;
  bool get isFailed => false;
  bool get isDone => false;
}


void showSpinner() {}
void showRetry() {}
void showResult() {}


void render(Status status) {
  if (status.isPending) {
    showSpinner();
  } else if (status.isFailed) {
    showRetry();
  } else if (status.isDone) {
    showResult();
  }
}

Known limitations

Section titled “Known limitations”

Conditions are compared by source text, so two spellings of the same test (a && b and b && a) are not reported.

Only one chain is compared at a time. Two independent if statements are never reported against each other, because the first may have changed the state the second reads:

class Cart {
  bool get isEmpty => true;


  void addDefaultItem() {}
  void showCheckout() {}
}


void prepare(Cart cart) {
  if (cart.isEmpty) {
    cart.addDefaultItem();
  }


  // Not reported — the block above may have changed the answer.
  if (cart.isEmpty) {
    cart.showCheckout();
  }
}

A pattern if (if (x case ...)) is skipped entirely: two clauses that read alike need not test the same thing.

Turning this rule off

Section titled “Turning this rule off”

This rule is in the recommended preset, so it is on with preset: recommended or preset: opinionated.

To disable this rule:

many_lints.yaml
rules:
  no_equal_conditions: false

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

Section titled “Related rules”