Add components

slider/node_modules/eslint/lib/rules/operator-assignment.js

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+/**
+ * @fileoverview Rule to replace assignment expressions with operator assignment
+ * @author Brandon Mills
+ */
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const astUtils = require("./utils/ast-utils");
+
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+/**
+ * Checks whether an operator is commutative and has an operator assignment
+ * shorthand form.
+ * @param {string} operator Operator to check.
+ * @returns {boolean} True if the operator is commutative and has a
+ *     shorthand form.
+ */
+function isCommutativeOperatorWithShorthand(operator) {
+	return ["*", "&", "^", "|"].includes(operator);
+}
+
+/**
+ * Checks whether an operator is not commutative and has an operator assignment
+ * shorthand form.
+ * @param {string} operator Operator to check.
+ * @returns {boolean} True if the operator is not commutative and has
+ *     a shorthand form.
+ */
+function isNonCommutativeOperatorWithShorthand(operator) {
+	return ["+", "-", "/", "%", "<<", ">>", ">>>", "**"].includes(operator);
+}
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+/**
+ * Determines if the left side of a node can be safely fixed (i.e. if it activates the same getters/setters and)
+ * toString calls regardless of whether assignment shorthand is used)
+ * @param {ASTNode} node The node on the left side of the expression
+ * @returns {boolean} `true` if the node can be fixed
+ */
+function canBeFixed(node) {
+	return (
+		node.type === "Identifier" ||
+		(node.type === "MemberExpression" &&
+			(node.object.type === "Identifier" ||
+				node.object.type === "ThisExpression") &&
+			(!node.computed || node.property.type === "Literal"))
+	);
+}
+
+/** @type {import('../types').Rule.RuleModule} */
+module.exports = {
+	meta: {
+		type: "suggestion",
+
+		defaultOptions: ["always"],
+
+		docs: {
+			description:
+				"Require or disallow assignment operator shorthand where possible",
+			recommended: false,
+			frozen: true,
+			url: "https://eslint.org/docs/latest/rules/operator-assignment",
+		},
+
+		schema: [
+			{
+				enum: ["always", "never"],
+			},
+		],
+
+		fixable: "code",
+		messages: {
+			replaced:
+				"Assignment (=) can be replaced with operator assignment ({{operator}}).",
+			unexpected:
+				"Unexpected operator assignment ({{operator}}) shorthand.",
+		},
+	},
+
+	create(context) {
+		const never = context.options[0] === "never";
+		const sourceCode = context.sourceCode;
+
+		/**
+		 * Returns the operator token of an AssignmentExpression or BinaryExpression
+		 * @param {ASTNode} node An AssignmentExpression or BinaryExpression node
+		 * @returns {Token} The operator token in the node
+		 */
+		function getOperatorToken(node) {
+			return sourceCode.getFirstTokenBetween(
+				node.left,
+				node.right,
+				token => token.value === node.operator,
+			);
+		}
+
+		/**
+		 * Ensures that an assignment uses the shorthand form where possible.
+		 * @param {ASTNode} node An AssignmentExpression node.
+		 * @returns {void}
+		 */
+		function verify(node) {
+			if (
+				node.operator !== "=" ||
+				node.right.type !== "BinaryExpression"
+			) {
+				return;
+			}
+
+			const left = node.left;
+			const expr = node.right;
+			const operator = expr.operator;
+
+			if (
+				isCommutativeOperatorWithShorthand(operator) ||
+				isNonCommutativeOperatorWithShorthand(operator)
+			) {
+				const replacementOperator = `${operator}=`;
+
+				if (astUtils.isSameReference(left, expr.left, true)) {
+					context.report({
+						node,
+						messageId: "replaced",
+						data: { operator: replacementOperator },
+						fix(fixer) {
+							if (canBeFixed(left) && canBeFixed(expr.left)) {
+								const equalsToken = getOperatorToken(node);
+								const operatorToken = getOperatorToken(expr);
+								const leftText = sourceCode
+									.getText()
+									.slice(node.range[0], equalsToken.range[0]);
+								const rightText = sourceCode
+									.getText()
+									.slice(
+										operatorToken.range[1],
+										node.right.range[1],
+									);
+
+								// Check for comments that would be removed.
+								if (
+									sourceCode.commentsExistBetween(
+										equalsToken,
+										operatorToken,
+									)
+								) {
+									return null;
+								}
+
+								return fixer.replaceText(
+									node,
+									`${leftText}${replacementOperator}${rightText}`,
+								);
+							}
+							return null;
+						},
+					});
+				} else if (
+					astUtils.isSameReference(left, expr.right, true) &&
+					isCommutativeOperatorWithShorthand(operator)
+				) {
+					/*
+					 * This case can't be fixed safely.
+					 * If `a` and `b` both have custom valueOf() behavior, then fixing `a = b * a` to `a *= b` would
+					 * change the execution order of the valueOf() functions.
+					 */
+					context.report({
+						node,
+						messageId: "replaced",
+						data: { operator: replacementOperator },
+					});
+				}
+			}
+		}
+
+		/**
+		 * Warns if an assignment expression uses operator assignment shorthand.
+		 * @param {ASTNode} node An AssignmentExpression node.
+		 * @returns {void}
+		 */
+		function prohibit(node) {
+			if (
+				node.operator !== "=" &&
+				!astUtils.isLogicalAssignmentOperator(node.operator)
+			) {
+				context.report({
+					node,
+					messageId: "unexpected",
+					data: { operator: node.operator },
+					fix(fixer) {
+						if (canBeFixed(node.left)) {
+							const firstToken = sourceCode.getFirstToken(node);
+							const operatorToken = getOperatorToken(node);
+							const leftText = sourceCode
+								.getText()
+								.slice(node.range[0], operatorToken.range[0]);
+							const newOperator = node.operator.slice(0, -1);
+							let rightText;
+
+							// Check for comments that would be duplicated.
+							if (
+								sourceCode.commentsExistBetween(
+									firstToken,
+									operatorToken,
+								)
+							) {
+								return null;
+							}
+
+							// If this change would modify precedence (e.g. `foo *= bar + 1` => `foo = foo * (bar + 1)`), parenthesize the right side.
+							if (
+								astUtils.getPrecedence(node.right) <=
+									astUtils.getPrecedence({
+										type: "BinaryExpression",
+										operator: newOperator,
+									}) &&
+								!astUtils.isParenthesised(
+									sourceCode,
+									node.right,
+								)
+							) {
+								rightText = `${sourceCode.text.slice(operatorToken.range[1], node.right.range[0])}(${sourceCode.getText(node.right)})`;
+							} else {
+								const tokenAfterOperator =
+									sourceCode.getTokenAfter(operatorToken, {
+										includeComments: true,
+									});
+								let rightTextPrefix = "";
+
+								if (
+									operatorToken.range[1] ===
+										tokenAfterOperator.range[0] &&
+									!astUtils.canTokensBeAdjacent(
+										{
+											type: "Punctuator",
+											value: newOperator,
+										},
+										tokenAfterOperator,
+									)
+								) {
+									rightTextPrefix = " "; // foo+=+bar -> foo= foo+ +bar
+								}
+
+								rightText = `${rightTextPrefix}${sourceCode.text.slice(operatorToken.range[1], node.range[1])}`;
+							}
+
+							return fixer.replaceText(
+								node,
+								`${leftText}= ${leftText}${newOperator}${rightText}`,
+							);
+						}
+						return null;
+					},
+				});
+			}
+		}
+
+		return {
+			AssignmentExpression: !never ? verify : prohibit,
+		};
+	},
+};