#no-fallthrough

#Configuration

import { defineConfig, js } from '@rslint/core';

export default defineConfig([
  js.configs.recommended,
  {
    rules: {
      'no-fallthrough': 'error',
    },
  },
]);

#Rule Details

Disallow fallthrough of case statements. A case clause that has statements but does not end with a control flow statement (break, return, throw, continue) will fall through to the next case, which is usually a programming error. Empty case clauses (with no statements) are allowed by default.

A comment containing "falls through" or "fall through" (case-insensitive) between the current case and the next will suppress the warning.

Examples of incorrect code for this rule:

switch (foo) {
  case 0:
    a();
  case 1:
    b();
    break;
}

switch (foo) {
  case 0:
    a();
  default:
    b();
}

Examples of correct code for this rule:

switch (foo) {
  case 0:
    a();
    break;
  case 1:
    b();
    break;
}

switch (foo) {
  case 0:
  case 1:
    a();
    break;
}

switch (foo) {
  case 0:
    a();
  /* falls through */
  case 1:
    b();
    break;
}

function bar() {
  switch (foo) {
    case 0:
      a();
      return;
    case 1:
      b();
  }
}

#Options

#commentPattern

A custom regular expression pattern to match fallthrough comments. By default matches /falls?\s?through/i.

{ "no-fallthrough": ["error", { "commentPattern": "break[\\s\\w]*omitted" }] }

#allowEmptyCase

When set to true, allows case clauses containing only empty statements (;) to fall through without a comment.

{ "no-fallthrough": ["error", { "allowEmptyCase": true }] }

#reportUnusedFallthroughComment

When set to true, reports fallthrough comments on cases that cannot actually fall through (e.g., cases ending with break).

{ "no-fallthrough": ["error", { "reportUnusedFallthroughComment": true }] }

#Original Documentation

https://eslint.org/docs/latest/rules/no-fallthrough