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prefer-includes.ts
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prefer-includes.ts
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/**
* @fileoverview Enforce `includes` method over `indexOf` method.
* @author Toru Nagashima <https://github.com/mysticatea>
*/
import { TSESTree } from '@typescript-eslint/typescript-estree';
import { getStaticValue } from 'eslint-utils';
import { AST as RegExpAST, parseRegExpLiteral } from 'regexpp';
import ts from 'typescript';
import { createRule, getParserServices } from '../util';
export default createRule({
name: 'prefer-includes',
defaultOptions: [],
meta: {
type: 'suggestion',
docs: {
description: 'Enforce `includes` method over `indexOf` method',
category: 'Best Practices',
recommended: false,
},
fixable: 'code',
messages: {
preferIncludes: "Use 'includes()' method instead.",
preferStringIncludes:
'Use `String#includes()` method with a string instead.',
},
schema: [],
},
create(context) {
const globalScope = context.getScope();
const services = getParserServices(context);
const types = services.program.getTypeChecker();
function isNumber(node: TSESTree.Node, value: number): boolean {
const evaluated = getStaticValue(node, globalScope);
return evaluated !== null && evaluated.value === value;
}
function isPositiveCheck(node: TSESTree.BinaryExpression): boolean {
switch (node.operator) {
case '!==':
case '!=':
case '>':
return isNumber(node.right, -1);
case '>=':
return isNumber(node.right, 0);
default:
return false;
}
}
function isNegativeCheck(node: TSESTree.BinaryExpression): boolean {
switch (node.operator) {
case '===':
case '==':
case '<=':
return isNumber(node.right, -1);
case '<':
return isNumber(node.right, 0);
default:
return false;
}
}
function hasSameParameters(
nodeA: ts.Declaration,
nodeB: ts.Declaration,
): boolean {
if (!ts.isFunctionLike(nodeA) || !ts.isFunctionLike(nodeB)) {
return false;
}
const paramsA = nodeA.parameters;
const paramsB = nodeB.parameters;
if (paramsA.length !== paramsB.length) {
return false;
}
for (let i = 0; i < paramsA.length; ++i) {
const paramA = paramsA[i];
const paramB = paramsB[i];
// Check name, type, and question token once.
if (paramA.getText() !== paramB.getText()) {
return false;
}
}
return true;
}
/**
* Parse a given node if it's a `RegExp` instance.
* @param node The node to parse.
*/
function parseRegExp(node: TSESTree.Node): string | null {
const evaluated = getStaticValue(node, globalScope);
if (evaluated == null || !(evaluated.value instanceof RegExp)) {
return null;
}
const { pattern, flags } = parseRegExpLiteral(evaluated.value);
if (
pattern.alternatives.length !== 1 ||
flags.ignoreCase ||
flags.global
) {
return null;
}
// Check if it can determine a unique string.
const chars = pattern.alternatives[0].elements;
if (!chars.every(c => c.type === 'Character')) {
return null;
}
// To string.
return String.fromCodePoint(
...chars.map(c => (c as RegExpAST.Character).value),
);
}
return {
"BinaryExpression > CallExpression.left > MemberExpression.callee[property.name='indexOf'][computed=false]"(
node: TSESTree.MemberExpression,
): void {
// Check if the comparison is equivalent to `includes()`.
const callNode = node.parent as TSESTree.CallExpression;
const compareNode = callNode.parent as TSESTree.BinaryExpression;
const negative = isNegativeCheck(compareNode);
if (!negative && !isPositiveCheck(compareNode)) {
return;
}
// Get the symbol of `indexOf` method.
const tsNode = services.esTreeNodeToTSNodeMap.get(node.property);
const indexofMethodSymbol = types.getSymbolAtLocation(tsNode);
if (
indexofMethodSymbol == null ||
indexofMethodSymbol.declarations.length === 0
) {
return;
}
// Check if every declaration of `indexOf` method has `includes` method
// and the two methods have the same parameters.
for (const instanceofMethodDecl of indexofMethodSymbol.declarations) {
const typeDecl = instanceofMethodDecl.parent;
const type = types.getTypeAtLocation(typeDecl);
const includesMethodSymbol = type.getProperty('includes');
if (
includesMethodSymbol == null ||
!includesMethodSymbol.declarations.some(includesMethodDecl =>
hasSameParameters(includesMethodDecl, instanceofMethodDecl),
)
) {
return;
}
}
// Report it.
context.report({
node: compareNode,
messageId: 'preferIncludes',
*fix(fixer) {
if (negative) {
yield fixer.insertTextBefore(callNode, '!');
}
yield fixer.replaceText(node.property, 'includes');
yield fixer.removeRange([callNode.range[1], compareNode.range[1]]);
},
});
},
// /bar/.test(foo)
'CallExpression > MemberExpression.callee[property.name="test"][computed=false]'(
node: TSESTree.MemberExpression,
): void {
const callNode = node.parent as TSESTree.CallExpression;
const text =
callNode.arguments.length === 1 ? parseRegExp(node.object) : null;
if (text == null) {
return;
}
context.report({
node: callNode,
messageId: 'preferStringIncludes',
*fix(fixer) {
const argNode = callNode.arguments[0];
const needsParen =
argNode.type !== 'Literal' &&
argNode.type !== 'TemplateLiteral' &&
argNode.type !== 'Identifier' &&
argNode.type !== 'MemberExpression' &&
argNode.type !== 'CallExpression';
yield fixer.removeRange([callNode.range[0], argNode.range[0]]);
if (needsParen) {
yield fixer.insertTextBefore(argNode, '(');
yield fixer.insertTextAfter(argNode, ')');
}
yield fixer.insertTextAfter(
argNode,
`.includes(${JSON.stringify(text)}`,
);
},
});
},
};
},
});