forked from sindresorhus/eslint-plugin-unicorn
/
no-useless-undefined.js
126 lines (107 loc) · 3.2 KB
/
no-useless-undefined.js
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'use strict';
const {isCommaToken} = require('eslint-utils');
const getDocumentationUrl = require('./utils/get-documentation-url');
const messageId = 'no-useless-undefined';
const getSelector = (parent, property) =>
`${parent} > Identifier.${property}[name="undefined"]`;
// `return undefined`
const returnSelector = getSelector('ReturnStatement', 'argument');
// `yield undefined`
const yieldSelector = getSelector('YieldExpression[delegate=false]', 'argument');
// `() => undefined`
const arrowFunctionSelector = getSelector('ArrowFunctionExpression', 'body');
// `let foo = undefined` / `var foo = undefined`
const variableInitSelector = getSelector(
[
'VariableDeclaration',
'[kind!="const"]',
'>',
'VariableDeclarator'
].join(''),
'init'
);
// `const {foo = undefined} = {}`
const assignmentPatternSelector = getSelector('AssignmentPattern', 'right');
const isUndefined = node => node && node.type === 'Identifier' && node.name === 'undefined';
const create = context => {
const listener = fix => node => {
context.report({
node,
messageId,
fix: fixer => fix(node, fixer)
});
};
const code = context.getSourceCode().text;
const removeNodeAndLeadingSpace = (node, fixer) => {
const textBefore = code.slice(0, node.range[0]);
return fixer.removeRange([
node.range[0] - (textBefore.length - textBefore.trim().length),
node.range[1]
]);
};
return {
[returnSelector]: listener(removeNodeAndLeadingSpace),
[yieldSelector]: listener(removeNodeAndLeadingSpace),
[arrowFunctionSelector]: listener(
(node, fixer) => fixer.replaceText(node, '{}')
),
[variableInitSelector]: listener(
(node, fixer) => fixer.removeRange([node.parent.id.range[1], node.range[1]])
),
[assignmentPatternSelector]: listener(
(node, fixer) => fixer.removeRange([node.parent.left.range[1], node.range[1]])
),
CallExpression: node => {
const argumentNodes = node.arguments;
const undefinedArguments = [];
for (let index = argumentNodes.length - 1; index >= 0; index--) {
const node = argumentNodes[index];
if (isUndefined(node)) {
undefinedArguments.unshift(node);
} else {
break;
}
}
if (undefinedArguments.length === 0) {
return;
}
const firstUndefined = undefinedArguments[0];
const lastUndefined = undefinedArguments[undefinedArguments.length - 1];
context.report({
messageId,
loc: {
start: firstUndefined.loc.start,
end: lastUndefined.loc.end
},
fix: fixer => {
let start = firstUndefined.range[0];
let end = lastUndefined.range[1];
const previousArgument = argumentNodes[argumentNodes.length - undefinedArguments.length - 1];
if (previousArgument) {
start = previousArgument.range[1];
} else {
// If all arguments removed, and there is trailing comma, we need remove it.
const tokenAfter = context.getTokenAfter(lastUndefined);
if (isCommaToken(tokenAfter)) {
end = tokenAfter.range[1];
}
}
return fixer.removeRange([start, end]);
}
});
}
};
};
module.exports = {
create,
meta: {
type: 'suggestion',
docs: {
url: getDocumentationUrl(__filename)
},
messages: {
[messageId]: 'Do not use useless `undefined`.'
},
fixable: 'code'
}
};