8000 feat: add check to for-direction rule when the condition is in revers… · eslint/eslint@faeb3ee · GitHub
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AngeloCloudAcademyAngeloCloudAcademy
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feat: add check to for-direction rule when the condition is in reverse order
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‎docs/src/rules/for-direction.md‎

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Original file line numberDiff line numberDiff line change
@@ -24,6 +24,9 @@ for (var i = 10; i >= 0; i++) {
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for (var i = 0; i > 10; i++) {
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}
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for (var i = 0; 10 > i; i--) {
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}
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const n = -2;
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for (let i = 0; i < 10; i += n) {
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}
@@ -40,6 +43,9 @@ Examples of **correct** code for this rule:
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for (var i = 0; i < 10; i++) {
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}
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for (var i = 0; 10 > i; i++) { // with counter "i" on the right
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}
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for (let i = 10; i >= 0; i += this.step) { // direction unknown
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}
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‎lib/rules/for-direction.js‎

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Original file line numberDiff line numberDiff line change
@@ -101,20 +101,36 @@ module.exports = {
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}
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return 0;
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}
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/**
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* get the counter position in test
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* @param {ASTNode} node the node to check
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* @returns {"left" | "right"} the position of the counter respect to BinaryExpression
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*/
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function getCounterPosition(node) {
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if (node.update.type === "UpdateExpression" || node.update.type === "AssignmentExpression") {
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if (node.update.argument && node.update.argument.type === "Identifier") {
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return node.test.left.name === node.update.argument.name ? "left" : "right";
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}
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}
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return "left";
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}
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return {
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ForStatement(node) {
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if (node.test && node.test.type === "BinaryExpression" && node.test.left.type === "Identifier" && node.update) {
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const counter = node.test.left.name;
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if (node.test && node.test.type === "BinaryExpression" && (node.test.left.type === "Identifier" || node.test.right.type === "Identifier") && node.update) {
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const counterPosition = getCounterPosition(node);
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const counter = node.test[counterPosition].name;
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const operator = node.test.operator;
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const update = node.update;
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let wrongDirection;
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if (operator === "<" || operator === "<=") {
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wrongDirection = -1;
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wrongDirection = counterPosition === "left" ? -1 : 1;
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} else if (operator === ">" || operator === ">=") {
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wrongDirection = 1;
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wrongDirection = counterPosition === "left" ? 1 : -1;
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} else {
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return;
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}

‎tests/lib/rules/for-direction.js‎

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Original file line numberDiff line numberDiff line change
@@ -28,6 +28,12 @@ ruleTester.run("for-direction", rule, {
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"for(var i = 10; i > 0; i--){}",
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"for(var i = 10; i >= 0; i--){}",
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// test if '++', '--' with counter 'i' on the right side of test condition
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"for(var i = 0; 10 > i; i++){}",
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"for(var i = 0; 10 >= i; i++){}",
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"for(var i = 10; 0 < i; i--){}",
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"for(var i = 10; 0 <= i; i--){}",
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// test if '+=', '-=',
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"for(var i = 0; i < 10; i+=1){}",
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"for(var i = 0; i <= 10; i+=1){}",
@@ -82,6 +88,12 @@ ruleTester.run("for-direction", rule, {
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{ code: "for(var i = 10; i > 10; i++){}", errors: [incorrectDirection] },
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{ code: "for(var i = 10; i >= 0; i++){}", errors: [incorrectDirection] },
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// test if '++', '--' with counter 'i' on the right side of test condition
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{ code: "for(var i = 0; 10 > i; i--){}", errors: [incorrectDirection] },
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{ code: "for(var i = 0; 10 >= i; i--){}", errors: [incorrectDirection] },
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{ code: "for(var i = 10; 10 < i; i++){}", errors: [incorrectDirection] },
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{ code: "for(var i = 10; 0 <= i; i++){}", errors: [incorrectDirection] },
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// test if '+=', '-='
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{ code: "for(var i = 0; i < 10; i-=1){}", errors: [incorrectDirection] },
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{ code: "for(var i = 0; i <= 10; i-=1){}", errors: [incorrectDirection] },

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