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Refactor explicit-length-check #950

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merged 14 commits into from Dec 22, 2020
Merged

Refactor explicit-length-check #950

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18e90ef
Refactor `explicit-length-check`
fisker Dec 22, 2020
416769c
Style
fisker Dec 22, 2020
df5cd4e
Add `getRemovableBooleanParent`
fisker Dec 22, 2020
fafc2a4
Add `isLogicNotArgument`
fisker Dec 22, 2020
00b4b1b
Refactor to check from "inner"
fisker Dec 22, 2020
8e7fc1e
Combine selectors
fisker Dec 22, 2020
6db350e
Move `isNonZeroLengthCheck` `isZeroLengthCheck` logic to listener
fisker Dec 22, 2020
2d44488
Simplify
fisker Dec 22, 2020
9ef209f
Simplify
fisker Dec 22, 2020
ddb3e32
Clean
fisker Dec 22, 2020
d579985
Style
fisker Dec 22, 2020
981c5ac
Fix logic
fisker Dec 22, 2020
d1639fc
Coverage
fisker Dec 22, 2020
aafa45a
Rename
fisker Dec 22, 2020
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206 changes: 88 additions & 118 deletions rules/explicit-length-check.js
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@@ -1,6 +1,7 @@
'use strict';
const {isParenthesized} = require('eslint-utils');
const getDocumentationUrl = require('./utils/get-documentation-url');
const isLiteralValue = require('./utils/is-literal-value');

const TYPE_NON_ZERO = 'non-zero';
const TYPE_ZERO = 'zero';
Expand All @@ -9,28 +10,21 @@ const messages = {
[TYPE_ZERO]: 'Use `.length {{code}}` when checking length is zero.'
};

const isLengthProperty = node =>
node.type === 'MemberExpression' &&
node.computed === false &&
node.property.type === 'Identifier' &&
node.property.name === 'length';
const isLogicNot = node =>
node.type === 'UnaryExpression' &&
node.operator === '!';
const isLiteralNumber = (node, value) =>
node.type === 'Literal' &&
typeof node.value === 'number' &&
node.value === value;
const isLogicNotArgument = node =>
node.parent &&
isLogicNot(node.parent) &&
node.parent.argument === node;
const isCompareRight = (node, operator, value) =>
node.type === 'BinaryExpression' &&
node.operator === operator &&
isLengthProperty(node.left) &&
isLiteralNumber(node.right, value);
isLiteralValue(node.right, value);
const isCompareLeft = (node, operator, value) =>
node.type === 'BinaryExpression' &&
node.operator === operator &&
isLengthProperty(node.right) &&
isLiteralNumber(node.left, value);
isLiteralValue(node.left, value);
const nonZeroStyles = new Map([
[
'greater-than',
Expand Down Expand Up @@ -59,16 +53,44 @@ const zeroStyle = {
test: node => isCompareRight(node, '===', 0)
};

const cache = new WeakMap();
function getCheckTypeAndLengthNode(node) {
if (!cache.has(node)) {
cache.set(node, getCheckTypeAndLengthNodeWithoutCache(node));
const lengthSelector = [
'MemberExpression',
'[computed=false]',
'[property.type="Identifier"]',
'[property.name="length"]'
].join('');

function getBooleanAncestor(node) {
let isNegative = false;
while (isLogicNotArgument(node)) {
isNegative = !isNegative;
node = node.parent;
}

return cache.get(node);
return {node, isNegative};
}

function getCheckTypeAndLengthNodeWithoutCache(node) {
function getLengthCheckNode(node) {
node = node.parent;

// Zero length check
if (
// `foo.length === 0`
isCompareRight(node, '===', 0) ||
// `foo.length == 0`
isCompareRight(node, '==', 0) ||
// `foo.length < 1`
isCompareRight(node, '<', 1) ||
// `0 === foo.length`
isCompareLeft(node, '===', 0) ||
// `0 == foo.length`
isCompareLeft(node, '==', 0) ||
// `1 > foo.length`
isCompareLeft(node, '>', 1)
) {
return {isZeroLengthCheck: true, node};
}

// Non-Zero length check
if (
// `foo.length !== 0`
Expand All @@ -78,12 +100,7 @@ function getCheckTypeAndLengthNodeWithoutCache(node) {
// `foo.length > 0`
isCompareRight(node, '>', 0) ||
// `foo.length >= 1`
isCompareRight(node, '>=', 1)
) {
return {type: TYPE_NON_ZERO, node, lengthNode: node.left};
}

if (
isCompareRight(node, '>=', 1) ||
// `0 !== foo.length`
isCompareLeft(node, '!==', 0) ||
// `0 !== foo.length`
Expand All @@ -93,43 +110,37 @@ function getCheckTypeAndLengthNodeWithoutCache(node) {
// `1 <= foo.length`
isCompareLeft(node, '<=', 1)
) {
return {type: TYPE_NON_ZERO, node, lengthNode: node.right};
return {isZeroLengthCheck: false, node};
}

// Zero length check
if (
// `foo.length === 0`
isCompareRight(node, '===', 0) ||
// `foo.length == 0`
isCompareRight(node, '==', 0) ||
// `foo.length < 1`
isCompareRight(node, '<', 1)
) {
return {type: TYPE_ZERO, node, lengthNode: node.left};
return {};
}

function isBooleanNode(node) {
if (isLogicNot(node) || isLogicNotArgument(node)) {
return true;
}

const {parent} = node;
if (
// `0 === foo.length`
isCompareLeft(node, '===', 0) ||
// `0 == foo.length`
isCompareLeft(node, '==', 0) ||
// `1 > foo.length`
isCompareLeft(node, '>', 1)
(
parent.type === 'IfStatement' ||
parent.type === 'ConditionalExpression' ||
parent.type === 'WhileStatement' ||
parent.type === 'DoWhileStatement' ||
parent.type === 'ForStatement'
) &&
parent.test === node
) {
return {type: TYPE_ZERO, node, lengthNode: node.right};
return true;
}
}

// TODO: check other `LogicalExpression`s
const booleanNodeSelector = `:matches(${
[
'IfStatement',
'ConditionalExpression',
'WhileStatement',
'DoWhileStatement',
'ForStatement'
].join(', ')
}) > *.test`;
if (parent.type === 'LogicalExpression') {
return isBooleanNode(parent);
}

return false;
}

function create(context) {
const options = {
Expand All @@ -138,14 +149,13 @@ function create(context) {
};
const nonZeroStyle = nonZeroStyles.get(options['non-zero']);
const sourceCode = context.getSourceCode();
const reportedBinaryExpressions = new Set();

function reportProblem({node, type, lengthNode}, isNegative) {
if (isNegative) {
type = type === TYPE_NON_ZERO ? TYPE_ZERO : TYPE_NON_ZERO;
function reportProblem({node, isZeroLengthCheck, lengthNode}) {
const {code, test} = isZeroLengthCheck ? zeroStyle : nonZeroStyle;
if (test(node)) {
return;
}

const {code} = type === TYPE_NON_ZERO ? nonZeroStyle : zeroStyle;
let fixed = `${sourceCode.getText(lengthNode)} ${code}`;
if (
!isParenthesized(node, sourceCode) &&
Expand All @@ -157,74 +167,34 @@ function create(context) {

context.report({
node,
messageId: type,
messageId: isZeroLengthCheck ? TYPE_ZERO : TYPE_NON_ZERO,
data: {code},
fix: fixer => fixer.replaceText(node, fixed)
});
}

function checkBooleanNode(node) {
if (node.type === 'LogicalExpression') {
checkBooleanNode(node.left);
checkBooleanNode(node.right);
return;
}

if (isLengthProperty(node)) {
reportProblem({node, type: TYPE_NON_ZERO, lengthNode: node});
}
}

const binaryExpressions = [];
return {
// The outer `!` expression
'UnaryExpression[operator="!"]:not(UnaryExpression[operator="!"] > .argument)'(node) {
let isNegative = false;
let expression = node;
while (isLogicNot(expression)) {
isNegative = !isNegative;
expression = expression.argument;
}

if (expression.type === 'LogicalExpression') {
checkBooleanNode(expression);
return;
}

if (isLengthProperty(expression)) {
reportProblem({type: TYPE_NON_ZERO, node, lengthNode: expression}, isNegative);
return;
}

const result = getCheckTypeAndLengthNode(expression);
if (result) {
reportProblem({...result, node}, isNegative);
reportedBinaryExpressions.add(result.lengthNode);
}
},
[booleanNodeSelector](node) {
checkBooleanNode(node);
},
BinaryExpression(node) {
// Delay check on this, so we don't need take two steps for this case
// `const isEmpty = !(foo.length >= 1);`
binaryExpressions.push(node);
},
'Program:exit'() {
for (const node of binaryExpressions) {
if (
reportedBinaryExpressions.has(node) ||
zeroStyle.test(node) ||
nonZeroStyle.test(node)
) {
continue;
[lengthSelector](lengthNode) {
let node;

let {isZeroLengthCheck, node: lengthCheckNode} = getLengthCheckNode(lengthNode);
if (lengthCheckNode) {
const {isNegative, node: ancestor} = getBooleanAncestor(lengthCheckNode);
node = ancestor;
if (isNegative) {
isZeroLengthCheck = !isZeroLengthCheck;
}

const result = getCheckTypeAndLengthNode(node);
if (result) {
reportProblem(result);
} else {
const {isNegative, node: ancestor} = getBooleanAncestor(lengthNode);
if (isBooleanNode(ancestor)) {
isZeroLengthCheck = isNegative;
node = ancestor;
}
}

if (node) {
reportProblem({node, isZeroLengthCheck, lengthNode});
}
}
};
}
Expand Down