105 lines
3.1 KiB
JavaScript
105 lines
3.1 KiB
JavaScript
/**
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* @fileoverview Rule to flag use of unary increment and decrement operators.
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* @author Ian Christian Myers
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* @author Brody McKee (github.com/mrmckeb)
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Helpers
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//------------------------------------------------------------------------------
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/**
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* Determines whether the given node is the update node of a `ForStatement`.
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* @param {ASTNode} node The node to check.
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* @returns {boolean} `true` if the node is `ForStatement` update.
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*/
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function isForStatementUpdate(node) {
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const parent = node.parent;
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return parent.type === "ForStatement" && parent.update === node;
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}
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/**
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* Determines whether the given node is considered to be a for loop "afterthought" by the logic of this rule.
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* In particular, it returns `true` if the given node is either:
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* - The update node of a `ForStatement`: for (;; i++) {}
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* - An operand of a sequence expression that is the update node: for (;; foo(), i++) {}
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* - An operand of a sequence expression that is child of another sequence expression, etc.,
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* up to the sequence expression that is the update node: for (;; foo(), (bar(), (baz(), i++))) {}
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* @param {ASTNode} node The node to check.
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* @returns {boolean} `true` if the node is a for loop afterthought.
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*/
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function isForLoopAfterthought(node) {
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const parent = node.parent;
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if (parent.type === "SequenceExpression") {
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return isForLoopAfterthought(parent);
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}
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return isForStatementUpdate(node);
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}
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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/** @type {import('../shared/types').Rule} */
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module.exports = {
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meta: {
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type: "suggestion",
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docs: {
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description: "disallow the unary operators `++` and `--`",
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recommended: false,
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url: "https://eslint.org/docs/rules/no-plusplus"
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},
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schema: [
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{
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type: "object",
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properties: {
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allowForLoopAfterthoughts: {
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type: "boolean",
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default: false
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}
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},
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additionalProperties: false
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}
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],
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messages: {
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unexpectedUnaryOp: "Unary operator '{{operator}}' used."
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}
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},
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create(context) {
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const config = context.options[0];
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let allowForLoopAfterthoughts = false;
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if (typeof config === "object") {
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allowForLoopAfterthoughts = config.allowForLoopAfterthoughts === true;
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}
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return {
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UpdateExpression(node) {
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if (allowForLoopAfterthoughts && isForLoopAfterthought(node)) {
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return;
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}
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context.report({
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node,
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messageId: "unexpectedUnaryOp",
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data: {
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operator: node.operator
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}
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});
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}
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};
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}
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};
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