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git.proxmox.com Git - pve-eslint.git/blob - eslint/lib/rules/operator-assignment.js
2 * @fileoverview Rule to replace assignment expressions with operator assignment
3 * @author Brandon Mills
7 //------------------------------------------------------------------------------
9 //------------------------------------------------------------------------------
11 const astUtils
= require("./utils/ast-utils");
13 //------------------------------------------------------------------------------
15 //------------------------------------------------------------------------------
18 * Checks whether an operator is commutative and has an operator assignment
20 * @param {string} operator Operator to check.
21 * @returns {boolean} True if the operator is commutative and has a
24 function isCommutativeOperatorWithShorthand(operator
) {
25 return ["*", "&", "^", "|"].indexOf(operator
) >= 0;
29 * Checks whether an operator is not commutative and has an operator assignment
31 * @param {string} operator Operator to check.
32 * @returns {boolean} True if the operator is not commutative and has
35 function isNonCommutativeOperatorWithShorthand(operator
) {
36 return ["+", "-", "/", "%", "<<", ">>", ">>>", "**"].indexOf(operator
) >= 0;
39 //------------------------------------------------------------------------------
41 //------------------------------------------------------------------------------
44 * Determines if the left side of a node can be safely fixed (i.e. if it activates the same getters/setters and)
45 * toString calls regardless of whether assignment shorthand is used)
46 * @param {ASTNode} node The node on the left side of the expression
47 * @returns {boolean} `true` if the node can be fixed
49 function canBeFixed(node
) {
51 node
.type
=== "Identifier" ||
53 node
.type
=== "MemberExpression" &&
54 (node
.object
.type
=== "Identifier" || node
.object
.type
=== "ThisExpression") &&
55 (!node
.computed
|| node
.property
.type
=== "Literal")
65 description
: "require or disallow assignment operator shorthand where possible",
66 category
: "Stylistic Issues",
68 url
: "https://eslint.org/docs/rules/operator-assignment"
73 enum: ["always", "never"]
79 replaced
: "Assignment can be replaced with operator assignment.",
80 unexpected
: "Unexpected operator assignment shorthand."
86 const sourceCode
= context
.getSourceCode();
89 * Returns the operator token of an AssignmentExpression or BinaryExpression
90 * @param {ASTNode} node An AssignmentExpression or BinaryExpression node
91 * @returns {Token} The operator token in the node
93 function getOperatorToken(node
) {
94 return sourceCode
.getFirstTokenBetween(node
.left
, node
.right
, token
=> token
.value
=== node
.operator
);
98 * Ensures that an assignment uses the shorthand form where possible.
99 * @param {ASTNode} node An AssignmentExpression node.
102 function verify(node
) {
103 if (node
.operator
!== "=" || node
.right
.type
!== "BinaryExpression") {
107 const left
= node
.left
;
108 const expr
= node
.right
;
109 const operator
= expr
.operator
;
111 if (isCommutativeOperatorWithShorthand(operator
) || isNonCommutativeOperatorWithShorthand(operator
)) {
112 if (astUtils
.isSameReference(left
, expr
.left
, true)) {
115 messageId
: "replaced",
117 if (canBeFixed(left
) && canBeFixed(expr
.left
)) {
118 const equalsToken
= getOperatorToken(node
);
119 const operatorToken
= getOperatorToken(expr
);
120 const leftText
= sourceCode
.getText().slice(node
.range
[0], equalsToken
.range
[0]);
121 const rightText
= sourceCode
.getText().slice(operatorToken
.range
[1], node
.right
.range
[1]);
123 // Check for comments that would be removed.
124 if (sourceCode
.commentsExistBetween(equalsToken
, operatorToken
)) {
128 return fixer
.replaceText(node
, `${leftText}${expr.operator}=${rightText}`);
133 } else if (astUtils
.isSameReference(left
, expr
.right
, true) && isCommutativeOperatorWithShorthand(operator
)) {
136 * This case can't be fixed safely.
137 * If `a` and `b` both have custom valueOf() behavior, then fixing `a = b * a` to `a *= b` would
138 * change the execution order of the valueOf() functions.
142 messageId
: "replaced"
149 * Warns if an assignment expression uses operator assignment shorthand.
150 * @param {ASTNode} node An AssignmentExpression node.
153 function prohibit(node
) {
154 if (node
.operator
!== "=" && !astUtils
.isLogicalAssignmentOperator(node
.operator
)) {
157 messageId
: "unexpected",
159 if (canBeFixed(node
.left
)) {
160 const firstToken
= sourceCode
.getFirstToken(node
);
161 const operatorToken
= getOperatorToken(node
);
162 const leftText
= sourceCode
.getText().slice(node
.range
[0], operatorToken
.range
[0]);
163 const newOperator
= node
.operator
.slice(0, -1);
166 // Check for comments that would be duplicated.
167 if (sourceCode
.commentsExistBetween(firstToken
, operatorToken
)) {
171 // If this change would modify precedence (e.g. `foo *= bar + 1` => `foo = foo * (bar + 1)`), parenthesize the right side.
173 astUtils
.getPrecedence(node
.right
) <= astUtils
.getPrecedence({ type
: "BinaryExpression", operator
: newOperator
}) &&
174 !astUtils
.isParenthesised(sourceCode
, node
.right
)
176 rightText
= `${sourceCode.text.slice(operatorToken.range[1], node.right.range[0])}(${sourceCode.getText(node.right)})`;
178 const tokenAfterOperator
= sourceCode
.getTokenAfter(operatorToken
, { includeComments
: true });
179 let rightTextPrefix
= "";
182 operatorToken
.range
[1] === tokenAfterOperator
.range
[0] &&
183 !astUtils
.canTokensBeAdjacent({ type
: "Punctuator", value
: newOperator
}, tokenAfterOperator
)
185 rightTextPrefix
= " "; // foo+=+bar -> foo= foo+ +bar
188 rightText
= `${rightTextPrefix}${sourceCode.text.slice(operatorToken.range[1], node.range[1])}`;
191 return fixer
.replaceText(node
, `${leftText}= ${leftText}${newOperator}${rightText}`);
200 AssignmentExpression
: context
.options
[0] !== "never" ? verify
: prohibit