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feat: correct update direction in for-direction #17483

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merged 4 commits into from Aug 23, 2023
+48 −12
Merged

feat: correct update direction in for-direction #17483

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191548a
feat: correct update direction in `for-direction`
fasttime Aug 21, 2023
33b13a9
Improve documentation
fasttime Aug 22, 2023
1d38ba9
Update rule overview
fasttime Aug 22, 2023
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fasttime Aug 22, 2023
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23 changes: 15 additions & 8 deletions lib/rules/for-direction.js
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Expand Up @@ -5,6 +5,12 @@

"use strict";

//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------

const { getStaticValue } = require("@eslint-community/eslint-utils");

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
Expand All @@ -29,6 +35,7 @@ module.exports = {
},

create(context) {
const { sourceCode } = context;

/**
* report an error.
Expand All @@ -46,17 +53,17 @@ module.exports = {
* check the right side of the assignment
* @param {ASTNode} update UpdateExpression to check
* @param {int} dir expected direction that could either be turned around or invalidated
* @returns {int} return dir, the negated dir or zero if it's not clear for identifiers
* @returns {int} return dir, the negated dir, or zero if the counter does not change or the direction is not clear
*/
function getRightDirection(update, dir) {
if (update.right.type === "UnaryExpression") {
if (update.right.operator === "-") {
return -dir;
}
} else if (update.right.type === "Identifier") {
return 0;
const staticValue = getStaticValue(update.right, sourceCode.getScope(update));

if (staticValue && ["bigint", "boolean", "number"].includes(typeof staticValue.value)) {
const sign = Math.sign(Number(staticValue.value)) || 0; // convert NaN to 0

return dir * sign;
}
return dir;
return 0;
}

/**
Expand Down
23 changes: 21 additions & 2 deletions tests/lib/rules/for-direction.js
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Expand Up @@ -16,7 +16,7 @@ const { RuleTester } = require("../../../lib/rule-tester");
// Tests
//------------------------------------------------------------------------------

const ruleTester = new RuleTester();
const ruleTester = new RuleTester({ parserOptions: { ecmaVersion: 2020 } });
const incorrectDirection = { messageId: "incorrectDirection" };

ruleTester.run("for-direction", rule, {
Expand All @@ -37,6 +37,12 @@ ruleTester.run("for-direction", rule, {
"for(var i = 10; i >= 0; i-=1){}",
"for(var i = 10; i > 0; i+=-1){}",
"for(var i = 10; i >= 0; i+=-1){}",
"for(var i = 0n; i > l; i-=1n){}",
"for(var i = 0n; i < l; i-=-1n){}",
"for(var i = MIN; i <= MAX; i+=true){}",
"for(var i = 0; i < 10; i+=+5e-7){}",
"for(var i = 0; i < MAX; i -= ~2);",
"for(var i = 0, n = -1; i < MAX; i += -n);",

// test if no update.
"for(var i = 10; i > 0;){}",
Expand All @@ -54,6 +60,13 @@ ruleTester.run("for-direction", rule, {
"for(var i = 0; i < MAX; i += STEP_SIZE);",
"for(var i = 0; i < MAX; i -= STEP_SIZE);",
"for(var i = 10; i > 0; i += STEP_SIZE);",
"for(var i = 10; i >= 0; i += 0);",
"for(var i = 10n; i >= 0n; i += 0n);",
"for(var i = 10; i >= 0; i += this.step);",
"for(var i = 10; i >= 0; i += 'foo');",
"for(var i = 10; i > 0; i += !foo);",
"for(var i = MIN; i <= MAX; i -= false);",
"for(var i = MIN; i <= MAX; i -= 0/0);",

// other cond-expressions.
"for(var i = 0; i !== 10; i+=1){}",
Expand All @@ -77,6 +90,12 @@ ruleTester.run("for-direction", rule, {
{ code: "for(var i = 0; i < 10; i+=-1){}", errors: [incorrectDirection] },
{ code: "for(var i = 0; i <= 10; i+=-1){}", errors: [incorrectDirection] },
{ code: "for(var i = 10; i > 10; i-=-1){}", errors: [incorrectDirection] },
{ code: "for(var i = 10; i >= 0; i-=-1){}", errors: [incorrectDirection] }
{ code: "for(var i = 10; i >= 0; i-=-1){}", errors: [incorrectDirection] },
{ code: "for(var i = 0n; i > l; i+=1n){}", errors: [incorrectDirection] },
{ code: "for(var i = 0n; i < l; i+=-1n){}", errors: [incorrectDirection] },
{ code: "for(var i = MIN; i <= MAX; i-=true){}", errors: [incorrectDirection] },
{ code: "for(var i = 0; i < 10; i-=+5e-7){}", errors: [incorrectDirection] },
{ code: "for(var i = 0; i < MAX; i += (2 - 3));", errors: [incorrectDirection] },
{ code: "var n = -2; for(var i = 0; i < 10; i += n);", errors: [incorrectDirection] }
]
});