no-identical-conditions.md

no-identical-conditions

A chain of if-else-if and switch-case statements is evaluated from top to bottom. At most, only one branch will be executed: the first one with a condition that evaluates to true or that matches the discriminant of the switch.

Therefore, duplicating a condition automatically leads to dead code. Usually, this is due to a copy/paste error. At best, it's simply dead code and at worst, it's a bug that is likely to induce further bugs as the code is maintained, and obviously it could lead to unexpected behavior.

Noncompliant Code Example

if (param == 1) {
  openWindow();
} else if (param == 2) {
  closeWindow();
} else if (param == 1) { // Noncompliant
  moveWindowToTheBackground();
}

switch (param) {
  case 1:
    openWindow();
    break;
  case 2:
    closeWindow();
    break;
  case 1: // Noncompliant
    moveWindowToTheBackground();
    break;
}

Compliant Solution

if (param == 1) openWindow();
else if (param == 2) closeWindow();
else if (param == 3) moveWindowToTheBackground();

switch (param) {
  case 1:
    openWindow();
    break;
  case 2:
    closeWindow();
    break;
  case 3:
    moveWindowToTheBackground();
    break;
}