.config/coc/extensions/node_modules/coc-prettier/node_modules/eslint/lib/rules/operator-assignment.js

   1 /**
   2  * @fileoverview Rule to replace assignment expressions with operator assignment
   3  * @author Brandon Mills
   4  */
   5 "use strict";
   6
   7 //------------------------------------------------------------------------------
   8 // Requirements
   9 //------------------------------------------------------------------------------
  10
  11 const astUtils = require("./utils/ast-utils");
  12
  13 //------------------------------------------------------------------------------
  14 // Helpers
  15 //------------------------------------------------------------------------------
  16
  17 /**
  18  * Checks whether an operator is commutative and has an operator assignment
  19  * shorthand form.
  20  * @param   {string}  operator Operator to check.
  21  * @returns {boolean}          True if the operator is commutative and has a
  22  *     shorthand form.
  23  */
  24 function isCommutativeOperatorWithShorthand(operator) {
  25     return ["*", "&", "^", "|"].indexOf(operator) >= 0;
  26 }
  27
  28 /**
  29  * Checks whether an operator is not commutative and has an operator assignment
  30  * shorthand form.
  31  * @param   {string}  operator Operator to check.
  32  * @returns {boolean}          True if the operator is not commutative and has
  33  *     a shorthand form.
  34  */
  35 function isNonCommutativeOperatorWithShorthand(operator) {
  36     return ["+", "-", "/", "%", "<<", ">>", ">>>", "**"].indexOf(operator) >= 0;
  37 }
  38
  39 //------------------------------------------------------------------------------
  40 // Rule Definition
  41 //------------------------------------------------------------------------------
  42
  43 /**
  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
  48  */
  49 function canBeFixed(node) {
  50     return (
  51         node.type === "Identifier" ||
  52         (
  53             node.type === "MemberExpression" &&
  54             (node.object.type === "Identifier" || node.object.type === "ThisExpression") &&
  55             (!node.computed || node.property.type === "Literal")
  56         )
  57     );
  58 }
  59
  60 module.exports = {
  61     meta: {
  62         type: "suggestion",
  63
  64         docs: {
  65             description: "require or disallow assignment operator shorthand where possible",
  66             category: "Stylistic Issues",
  67             recommended: false,
  68             url: "https://eslint.org/docs/rules/operator-assignment"
  69         },
  70
  71         schema: [
  72             {
  73                 enum: ["always", "never"]
  74             }
  75         ],
  76
  77         fixable: "code",
  78         messages: {
  79             replaced: "Assignment can be replaced with operator assignment.",
  80             unexpected: "Unexpected operator assignment shorthand."
  81         }
  82     },
  83
  84     create(context) {
  85
  86         const sourceCode = context.getSourceCode();
  87
  88         /**
  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
  92          */
  93         function getOperatorToken(node) {
  94             return sourceCode.getFirstTokenBetween(node.left, node.right, token => token.value === node.operator);
  95         }
  96
  97         /**
  98          * Ensures that an assignment uses the shorthand form where possible.
  99          * @param   {ASTNode} node An AssignmentExpression node.
 100          * @returns {void}
 101          */
 102         function verify(node) {
 103             if (node.operator !== "=" || node.right.type !== "BinaryExpression") {
 104                 return;
 105             }
 106
 107             const left = node.left;
 108             const expr = node.right;
 109             const operator = expr.operator;
 110
 111             if (isCommutativeOperatorWithShorthand(operator) || isNonCommutativeOperatorWithShorthand(operator)) {
 112                 if (astUtils.isSameReference(left, expr.left, true)) {
 113                     context.report({
 114                         node,
 115                         messageId: "replaced",
 116                         fix(fixer) {
 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]);
 122
 123                                 // Check for comments that would be removed.
 124                                 if (sourceCode.commentsExistBetween(equalsToken, operatorToken)) {
 125                                     return null;
 126                                 }
 127
 128                                 return fixer.replaceText(node, `${leftText}${expr.operator}=${rightText}`);
 129                             }
 130                             return null;
 131                         }
 132                     });
 133                 } else if (astUtils.isSameReference(left, expr.right, true) && isCommutativeOperatorWithShorthand(operator)) {
 134
 135                     /*
 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.
 139                      */
 140                     context.report({
 141                         node,
 142                         messageId: "replaced"
 143                     });
 144                 }
 145             }
 146         }
 147
 148         /**
 149          * Warns if an assignment expression uses operator assignment shorthand.
 150          * @param   {ASTNode} node An AssignmentExpression node.
 151          * @returns {void}
 152          */
 153         function prohibit(node) {
 154             if (node.operator !== "=" && !astUtils.isLogicalAssignmentOperator(node.operator)) {
 155                 context.report({
 156                     node,
 157                     messageId: "unexpected",
 158                     fix(fixer) {
 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);
 164                             let rightText;
 165
 166                             // Check for comments that would be duplicated.
 167                             if (sourceCode.commentsExistBetween(firstToken, operatorToken)) {
 168                                 return null;
 169                             }
 170
 171                             // If this change would modify precedence (e.g. `foo *= bar + 1` => `foo = foo * (bar + 1)`), parenthesize the right side.
 172                             if (
 173                                 astUtils.getPrecedence(node.right) <= astUtils.getPrecedence({ type: "BinaryExpression", operator: newOperator }) &&
 174                                 !astUtils.isParenthesised(sourceCode, node.right)
 175                             ) {
 176                                 rightText = `${sourceCode.text.slice(operatorToken.range[1], node.right.range[0])}(${sourceCode.getText(node.right)})`;
 177                             } else {
 178                                 const tokenAfterOperator = sourceCode.getTokenAfter(operatorToken, { includeComments: true });
 179                                 let rightTextPrefix = "";
 180
 181                                 if (
 182                                     operatorToken.range[1] === tokenAfterOperator.range[0] &&
 183                                     !astUtils.canTokensBeAdjacent({ type: "Punctuator", value: newOperator }, tokenAfterOperator)
 184                                 ) {
 185                                     rightTextPrefix = " "; // foo+=+bar -> foo= foo+ +bar
 186                                 }
 187
 188                                 rightText = `${rightTextPrefix}${sourceCode.text.slice(operatorToken.range[1], node.range[1])}`;
 189                             }
 190
 191                             return fixer.replaceText(node, `${leftText}= ${leftText}${newOperator}${rightText}`);
 192                         }
 193                         return null;
 194                     }
 195                 });
 196             }
 197         }
 198
 199         return {
 200             AssignmentExpression: context.options[0] !== "never" ? verify : prohibit
 201         };
 202
 203     }
 204 };