4 * Copyright 2019 Palantir Technologies, Inc.
6 * Licensed under the Apache License, Version 2.0 (the "License");
7 * you may not use this file except in compliance with the License.
8 * You may obtain a copy of the License at
10 * http://www.apache.org/licenses/LICENSE-2.0
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
18 Object.defineProperty(exports, "__esModule", { value: true });
19 var tslib_1 = require("tslib");
20 var tsutils = require("tsutils");
21 var ts = require("typescript");
22 var Lint = require("../index");
23 var TAUTOLOGY_DISCOVERED_ERROR_STRING = "Both sides of this equality comparison are the same, so the expression is either a tautology or a contradiction.";
24 var Rule = /** @class */ (function (_super) {
25 tslib_1.__extends(Rule, _super);
27 return _super !== null && _super.apply(this, arguments) || this;
29 Rule.prototype.apply = function (sourceFile) {
30 return this.applyWithFunction(sourceFile, walk);
33 description: Lint.Utils.dedent(templateObject_1 || (templateObject_1 = tslib_1.__makeTemplateObject(["\n Enforces that relational/equality binary operators does not take two equal variables/literals as operands.\n Expression like 3 === 3, someVar === someVar, \"1\" > \"1\" are either a tautology or contradiction, and will produce an error.\n "], ["\n Enforces that relational/equality binary operators does not take two equal variables/literals as operands.\n Expression like 3 === 3, someVar === someVar, \"1\" > \"1\" are either a tautology or contradiction, and will produce an error.\n "]))),
34 optionExamples: [true],
36 optionsDescription: "Not configurable.",
37 rationale: "Clean redundant code and unnecessary comparison of objects and literals.",
38 ruleName: "no-tautology-expression",
39 type: "functionality",
40 typescriptOnly: false,
43 }(Lint.Rules.AbstractRule));
45 function walk(context) {
46 var cb = function (node) {
47 if (tsutils.isBinaryExpression(node) && isRelationalOrLogicalOperator(node.operatorToken)) {
48 if ((tsutils.isStringLiteral(node.left) && tsutils.isStringLiteral(node.right)) ||
49 (tsutils.isNumericLiteral(node.left) && tsutils.isNumericLiteral(node.right))) {
50 if (node.left.text === node.right.text) {
51 context.addFailureAtNode(node, TAUTOLOGY_DISCOVERED_ERROR_STRING);
54 else if (tsutils.isIdentifier(node.left) && tsutils.isIdentifier(node.right)) {
55 if (node.left.text === node.right.text) {
56 context.addFailureAtNode(node, TAUTOLOGY_DISCOVERED_ERROR_STRING);
59 else if (tsutils.isPropertyAccessExpression(node.left) &&
60 tsutils.isPropertyAccessExpression(node.right)) {
61 if (node.left.expression.getText() === node.right.expression.getText()) {
62 if (node.left.name.text === node.right.name.text) {
63 context.addFailureAtNode(node, TAUTOLOGY_DISCOVERED_ERROR_STRING);
67 else if ((isBooleanLiteral(node.left) && isBooleanLiteral(node.right)) ||
68 (isNullLiteral(node.left) && isNullLiteral(node.right))) {
69 context.addFailureAtNode(node, TAUTOLOGY_DISCOVERED_ERROR_STRING);
72 return ts.forEachChild(node, cb);
74 return ts.forEachChild(context.sourceFile, cb);
76 function isNullLiteral(node) {
77 return node.kind === ts.SyntaxKind.NullKeyword;
79 function isBooleanLiteral(node) {
80 return node.kind === ts.SyntaxKind.TrueKeyword || node.kind === ts.SyntaxKind.FalseKeyword;
82 function isRelationalOrLogicalOperator(operator) {
84 ts.SyntaxKind.LessThanToken,
85 ts.SyntaxKind.GreaterThanToken,
86 ts.SyntaxKind.LessThanEqualsToken,
87 ts.SyntaxKind.GreaterThanEqualsToken,
88 ts.SyntaxKind.EqualsEqualsToken,
89 ts.SyntaxKind.EqualsEqualsEqualsToken,
90 ts.SyntaxKind.ExclamationEqualsToken,
91 ts.SyntaxKind.ExclamationEqualsEqualsToken,
92 ts.SyntaxKind.AmpersandAmpersandToken,
93 ts.SyntaxKind.BarBarToken,
94 ]).has(operator.kind);