| 1 | /**
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| 2 | * Requires to return early in a function.
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| 3 | *
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| 4 | * Types: `Boolean`
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| 5 | *
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| 6 | * Values:
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| 7 | * - `true`: disallow to use of else if the corresponding `if` block contain a return.
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| 8 | *
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| 9 | * #### Example
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| 10 | *
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| 11 | * ```js
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| 12 | * "requireEarlyReturn": true
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| 13 | * ```
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| 14 | *
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| 15 | * ##### Valid
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| 16 | *
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| 17 | * ```js
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| 18 | * function test() {
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| 19 | * if (x) {
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| 20 | * return x;
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| 21 | * }
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| 22 | * return y;
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| 23 | * }
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| 24 | * ```
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| 25 | *
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| 26 | * ##### Invalid
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| 27 | *
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| 28 | * ```js
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| 29 | * function test() {
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| 30 | * if (x) {
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| 31 | * return x;
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| 32 | * } else {
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| 33 | * return y;
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| 34 | * }
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| 35 | * }
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| 36 | * ```
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| 37 | */
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| 38 |
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| 39 | var assert = require('assert');
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| 40 |
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| 41 | module.exports = function() {};
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| 42 |
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| 43 | module.exports.prototype = {
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| 44 | configure: function(options) {
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| 45 | assert(
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| 46 | options === true,
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| 47 | this.getOptionName() + ' option allow only the `true` value'
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| 48 | );
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| 49 | },
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| 50 |
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| 51 | getOptionName: function() {
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| 52 | return 'requireEarlyReturn';
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| 53 | },
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| 54 |
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| 55 | check: function(file, errors) {
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| 56 | function addError(entity) {
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| 57 | errors.add(
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| 58 | 'Use of else after return',
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| 59 | entity
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| 60 | );
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| 61 | }
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| 62 |
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| 63 | // Check if the IfStatement node contain a ReturnStatement.
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| 64 | // If the node has a block, check all the statements in backward order to see if there is one.
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| 65 | // This is to ensure that code like this will still return true:
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| 66 | //
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| 67 | // if (true) {
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| 68 | // return;
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| 69 | // eval();
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| 70 | // }
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| 71 | function hasNodeReturn(node) {
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| 72 | if (node.type === 'BlockStatement') {
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| 73 | for (var i = node.body.length - 1; i >= 0; i--) {
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| 74 | if (node.body[i].type === 'ReturnStatement') {
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| 75 | return true;
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| 76 | }
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| 77 | }
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| 78 | return false;
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| 79 | }
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| 80 | return node.type === 'ReturnStatement';
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| 81 | }
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| 82 |
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| 83 | file.iterateNodesByType('IfStatement', function(node) {
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| 84 | if (!node.alternate) {
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| 85 | return;
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| 86 | }
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| 87 |
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| 88 | // Check if all the parents have a return statement, if not continue to the following IfStatement node.
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| 89 | //
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| 90 | // Example:
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| 91 | //
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| 92 | // if (foo) {
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| 93 | // return;
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| 94 | // } else if (bar) { <-- error
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| 95 | // bar();
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| 96 | // } else if (baz) { <-- safe
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| 97 | // return baz();
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| 98 | // } else { <-- safe
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| 99 | // bas();
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| 100 | // }
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| 101 | for (var nodeIf = node; nodeIf && nodeIf.type === 'IfStatement'; nodeIf = nodeIf.parentElement) {
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| 102 | if (nodeIf.alternate && !hasNodeReturn(nodeIf.consequent)) {
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| 103 | return;
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| 104 | }
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| 105 | }
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| 106 |
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| 107 | return addError(file.getPrevToken(file.getFirstNodeToken(node.alternate)));
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| 108 | });
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| 109 | }
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| 110 | };
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