1 | /**
|
2 | * @fileoverview Rule to flag statements that use != and == instead of !== and ===
|
3 | * @author Nicholas C. Zakas
|
4 | */
|
5 |
|
6 | ;
|
7 |
|
8 | //------------------------------------------------------------------------------
|
9 | // Requirements
|
10 | //------------------------------------------------------------------------------
|
11 |
|
12 | const astUtils = require("../ast-utils");
|
13 |
|
14 | //------------------------------------------------------------------------------
|
15 | // Rule Definition
|
16 | //------------------------------------------------------------------------------
|
17 |
|
18 | module.exports = {
|
19 | meta: {
|
20 | docs: {
|
21 | description: "require the use of `===` and `!==`",
|
22 | category: "Best Practices",
|
23 | recommended: false
|
24 | },
|
25 |
|
26 | schema: {
|
27 | anyOf: [
|
28 | {
|
29 | type: "array",
|
30 | items: [
|
31 | {
|
32 | enum: ["always"]
|
33 | },
|
34 | {
|
35 | type: "object",
|
36 | properties: {
|
37 | null: {
|
38 | enum: ["always", "never", "ignore"]
|
39 | }
|
40 | },
|
41 | additionalProperties: false
|
42 | }
|
43 | ],
|
44 | additionalItems: false
|
45 | },
|
46 | {
|
47 | type: "array",
|
48 | items: [
|
49 | {
|
50 | enum: ["smart", "allow-null"]
|
51 | }
|
52 | ],
|
53 | additionalItems: false
|
54 | }
|
55 | ]
|
56 | },
|
57 |
|
58 | fixable: "code"
|
59 | },
|
60 |
|
61 | create(context) {
|
62 | const config = context.options[0] || "always";
|
63 | const options = context.options[1] || {};
|
64 | const sourceCode = context.getSourceCode();
|
65 |
|
66 | const nullOption = (config === "always")
|
67 | ? options.null || "always"
|
68 | : "ignore";
|
69 | const enforceRuleForNull = (nullOption === "always");
|
70 | const enforceInverseRuleForNull = (nullOption === "never");
|
71 |
|
72 | /**
|
73 | * Checks if an expression is a typeof expression
|
74 | * @param {ASTNode} node The node to check
|
75 | * @returns {boolean} if the node is a typeof expression
|
76 | */
|
77 | function isTypeOf(node) {
|
78 | return node.type === "UnaryExpression" && node.operator === "typeof";
|
79 | }
|
80 |
|
81 | /**
|
82 | * Checks if either operand of a binary expression is a typeof operation
|
83 | * @param {ASTNode} node The node to check
|
84 | * @returns {boolean} if one of the operands is typeof
|
85 | * @private
|
86 | */
|
87 | function isTypeOfBinary(node) {
|
88 | return isTypeOf(node.left) || isTypeOf(node.right);
|
89 | }
|
90 |
|
91 | /**
|
92 | * Checks if operands are literals of the same type (via typeof)
|
93 | * @param {ASTNode} node The node to check
|
94 | * @returns {boolean} if operands are of same type
|
95 | * @private
|
96 | */
|
97 | function areLiteralsAndSameType(node) {
|
98 | return node.left.type === "Literal" && node.right.type === "Literal" &&
|
99 | typeof node.left.value === typeof node.right.value;
|
100 | }
|
101 |
|
102 | /**
|
103 | * Checks if one of the operands is a literal null
|
104 | * @param {ASTNode} node The node to check
|
105 | * @returns {boolean} if operands are null
|
106 | * @private
|
107 | */
|
108 | function isNullCheck(node) {
|
109 | return astUtils.isNullLiteral(node.right) || astUtils.isNullLiteral(node.left);
|
110 | }
|
111 |
|
112 | /**
|
113 | * Gets the location (line and column) of the binary expression's operator
|
114 | * @param {ASTNode} node The binary expression node to check
|
115 | * @param {string} operator The operator to find
|
116 | * @returns {Object} { line, column } location of operator
|
117 | * @private
|
118 | */
|
119 | function getOperatorLocation(node) {
|
120 | const opToken = sourceCode.getTokenAfter(node.left);
|
121 |
|
122 | return { line: opToken.loc.start.line, column: opToken.loc.start.column };
|
123 | }
|
124 |
|
125 | /**
|
126 | * Reports a message for this rule.
|
127 | * @param {ASTNode} node The binary expression node that was checked
|
128 | * @param {string} expectedOperator The operator that was expected (either '==', '!=', '===', or '!==')
|
129 | * @returns {void}
|
130 | * @private
|
131 | */
|
132 | function report(node, expectedOperator) {
|
133 | context.report({
|
134 | node,
|
135 | loc: getOperatorLocation(node),
|
136 | message: "Expected '{{expectedOperator}}' and instead saw '{{actualOperator}}'.",
|
137 | data: { expectedOperator, actualOperator: node.operator },
|
138 | fix(fixer) {
|
139 |
|
140 | // If the comparison is a `typeof` comparison or both sides are literals with the same type, then it's safe to fix.
|
141 | if (isTypeOfBinary(node) || areLiteralsAndSameType(node)) {
|
142 | const operatorToken = sourceCode.getFirstTokenBetween(
|
143 | node.left,
|
144 | node.right,
|
145 | token => token.value === node.operator
|
146 | );
|
147 |
|
148 | return fixer.replaceText(operatorToken, expectedOperator);
|
149 | }
|
150 | return null;
|
151 | }
|
152 | });
|
153 | }
|
154 |
|
155 | return {
|
156 | BinaryExpression(node) {
|
157 | const isNull = isNullCheck(node);
|
158 |
|
159 | if (node.operator !== "==" && node.operator !== "!=") {
|
160 | if (enforceInverseRuleForNull && isNull) {
|
161 | report(node, node.operator.slice(0, -1));
|
162 | }
|
163 | return;
|
164 | }
|
165 |
|
166 | if (config === "smart" && (isTypeOfBinary(node) ||
|
167 | areLiteralsAndSameType(node) || isNull)) {
|
168 | return;
|
169 | }
|
170 |
|
171 | if (!enforceRuleForNull && isNull) {
|
172 | return;
|
173 | }
|
174 |
|
175 | report(node, `${node.operator}=`);
|
176 | }
|
177 | };
|
178 |
|
179 | }
|
180 | };
|