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no-useless-intersection.ts
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no-useless-intersection.ts
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/*
* SonarQube JavaScript Plugin
* Copyright (C) 2011-2020 SonarSource SA
* mailto:info AT sonarsource DOT com
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 3 of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
// https://jira.sonarsource.com/browse/RSPEC-4335
import { Rule } from 'eslint';
import * as estree from 'estree';
import { TSESTree } from '@typescript-eslint/experimental-utils';
import { isRequiredParserServices } from '../utils/isRequiredParserServices';
export const rule: Rule.RuleModule = {
create(context: Rule.RuleContext) {
const services = context.parserServices;
if (isRequiredParserServices(services)) {
const ts = require('typescript');
return {
TSIntersectionType: (node: estree.Node) => {
const intersection = (node as unknown) as TSESTree.TSIntersectionType;
const anyOrNever = intersection.types.find(typeNode =>
['TSAnyKeyword', 'TSNeverKeyword'].includes(typeNode.type),
);
if (anyOrNever) {
context.report({
message: `Simplify this intersection as it always has type "${
anyOrNever.type === 'TSAnyKeyword' ? 'any' : 'never'
}".`,
node,
});
} else {
intersection.types.forEach(typeNode => {
const tp = services.program
.getTypeChecker()
.getTypeAtLocation(services.esTreeNodeToTSNodeMap.get(typeNode));
if (isTypeWithoutMembers(tp, ts)) {
context.report({
message: 'Remove this type without members or change this type intersection.',
node: (typeNode as unknown) as estree.Node,
});
}
});
}
},
};
}
return {};
},
};
function isTypeWithoutMembers(tp: any, ts: any): boolean {
return isNullLike(tp, ts) || (isEmptyInterface(tp) && isStandaloneInterface(tp.symbol, ts));
}
function isNullLike(tp: any, ts: any): boolean {
return (
Boolean(tp.flags & ts.TypeFlags.Null) ||
Boolean(tp.flags & ts.TypeFlags.Undefined) ||
Boolean(tp.flags & ts.TypeFlags.Void)
);
}
function isEmptyInterface(tp: any): boolean {
return tp.symbol && tp.symbol.members && tp.symbol.members.size === 0;
}
function isStandaloneInterface({ declarations }: any, ts: any) {
// there is no declarations for `{}`
// otherwise check that none of declarations has a heritage clause (`extends X` or `implements X`)
return (
!declarations ||
(declarations as any[]).every(declaration => {
return (
isInterfaceDeclaration(declaration, ts) && (declaration.heritageClauses || []).length === 0
);
})
);
}
function isInterfaceDeclaration(declaration: any, ts: any): boolean {
return declaration.kind === ts.SyntaxKind.InterfaceDeclaration;
}