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eranshabiJosh Goldberg
eranshabi
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Josh Goldberg
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[New Rule] add noAsyncWithoutAwait rule (#3945)
* add noAsyncWithoutAwait rule * fix lint * code review updates * allow return as well as await * remove unneeded lint ignore * improve rationale & fix performance issue * fixes according to review * finish fixing according to review * Initial feedback cleanups * Refactored to walk function
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‎src/configs/all.ts

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@@ -107,6 +107,7 @@ export const rules = {
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// "import-blacklist": no sensible default
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"label-position": true,
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"no-arg": true,
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"no-async-without-await": true,
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"no-bitwise": true,
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"no-conditional-assignment": true,
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"no-console": true,

‎src/rules/code-examples/noAsyncWithoutAwait.examples.ts

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/**
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* @license
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* Copyright 2018 Palantir Technologies, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import * as Lint from "../../index";
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export const codeExamples = [
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{
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config: Lint.Utils.dedent`
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"rules": { "no-async-without-await": true }
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`,
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description: "Do not use the async keyword if it is not needed",
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fail: Lint.Utils.dedent`
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async function f() {
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fetch();
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}
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async function f() {
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async function g() {
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await h();
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}
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}
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`,
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pass: Lint.Utils.dedent`
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async function f() {
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await fetch();
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}
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const f = async () => {
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await fetch();
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};
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const f = async () => {
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return 'value';
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};
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`,
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},
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];

‎src/rules/noAsyncWithoutAwaitRule.ts

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/**
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* @license
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* Copyright 2018 Palantir Technologies, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import * as tsutils from "tsutils";
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import * as ts from "typescript";
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import * as Lint from "../index";
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import { codeExamples } from "./code-examples/noAsyncWithoutAwait.examples";
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type FunctionNodeType =
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| ts.ArrowFunction
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| ts.FunctionDeclaration
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| ts.MethodDeclaration
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| ts.FunctionExpression;
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export class Rule extends Lint.Rules.AbstractRule {
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public static FAILURE_STRING =
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"Functions marked async must contain an await or return statement.";
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public static metadata: Lint.IRuleMetadata = {
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codeExamples,
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description: Rule.FAILURE_STRING,
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hasFix: false,
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optionExamples: [true],
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options: null,
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optionsDescription: "Not configurable.",
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/* tslint:disable:max-line-length */
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rationale: Lint.Utils.dedent`
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Marking a function as \`async\` without using \`await\` or returning a value inside it can lead to an unintended promise return and a larger transpiled output.
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Often the function can be synchronous and the \`async\` keyword is there by mistake.
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Return statements are allowed as sometimes it is desirable to wrap the returned value in a Promise.`,
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/* tslint:enable:max-line-length */
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ruleName: "no-async-without-await",
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type: "functionality",
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typescriptOnly: false,
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};
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public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
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return this.applyWithFunction(sourceFile, walk);
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}
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}
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function walk(context: Lint.WalkContext) {
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const reportFailureIfAsyncFunction = (node: FunctionNodeType) => {
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const asyncModifier = getAsyncModifier(node);
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if (asyncModifier !== undefined) {
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context.addFailureAt(
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asyncModifier.getStart(),
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asyncModifier.getEnd() - asyncModifier.getStart(),
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Rule.FAILURE_STRING,
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);
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}
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};
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const addFailureIfAsyncFunctionHasNoAwait = (node: FunctionNodeType) => {
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if (node.body === undefined) {
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reportFailureIfAsyncFunction(node);
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return;
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}
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if (
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!isShortArrowReturn(node) &&
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!functionBlockHasAwait(node.body) &&
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!functionBlockHasReturn(node.body)
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) {
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reportFailureIfAsyncFunction(node);
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}
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};
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return ts.forEachChild(context.sourceFile, function visitNode(node): void {
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if (
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tsutils.isArrowFunction(node) ||
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tsutils.isFunctionDeclaration(node) ||
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tsutils.isFunctionExpression(node) ||
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tsutils.isMethodDeclaration(node)
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) {
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addFailureIfAsyncFunctionHasNoAwait(node);
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}
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return ts.forEachChild(node, visitNode);
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});
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}
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const getAsyncModifier = (node: ts.Node) => {
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if (node.modifiers !== undefined) {
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return node.modifiers.find(modifier => modifier.kind === ts.SyntaxKind.AsyncKeyword);
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}
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return undefined;
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};
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const isReturn = (node: ts.Node): boolean => node.kind === ts.SyntaxKind.ReturnKeyword;
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const functionBlockHasAwait = (node: ts.Node): boolean => {
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if (tsutils.isAwaitExpression(node)) {
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return true;
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}
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if (
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node.kind === ts.SyntaxKind.ArrowFunction ||
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node.kind === ts.SyntaxKind.FunctionDeclaration
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) {
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return false;
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}
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return node.getChildren().some(functionBlockHasAwait);
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};
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const functionBlockHasReturn = (node: ts.Node): boolean => {
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if (isReturn(node)) {
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return true;
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}
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if (
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node.kind === ts.SyntaxKind.ArrowFunction ||
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node.kind === ts.SyntaxKind.FunctionDeclaration
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) {
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return false;
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}
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return node.getChildren().some(functionBlockHasReturn);
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};
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const isShortArrowReturn = (node: FunctionNodeType) =>
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node.kind === ts.SyntaxKind.ArrowFunction && node.body.kind !== ts.SyntaxKind.Block;

‎test/rules/no-async-without-await/test.ts.lint

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async function a(){
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~~~~~ [0]
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let b = 1;
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console.log(b);
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}
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async function a(){
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let b = 1;
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await console.log(b);
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}
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async function a(){
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let b = 1;
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console.log(await b());
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}
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async function a(){
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~~~~~ [0]
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let b = 1;
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let c = async () => {
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await fetch();
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};
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}
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async function a(){
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~~~~~ [Functions marked async must contain an await or return statement.]
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let b = 1;
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async function f() {
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await fetch();
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};
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}
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function a(){
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let b = 1;
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async function f() {
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~~~~~ [Functions marked async must contain an await or return statement.]
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fetch();
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};
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}
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const a = async () => {
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~~~~~ [Functions marked async must contain an await or return statement.]
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let b = 1;
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console.log(b);
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}
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class A {
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async b() {
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~~~~~ [Functions marked async must contain an await or return statement.]
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console.log(1);
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}
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}
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class A {
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async b() {
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await b();
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}
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}
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class A {
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public a = async function b() {
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await b();
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}
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}
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class A {
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public a = async function b() {
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~~~~~ [Functions marked async must contain an await or return statement.]
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b();
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}
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}
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class A {
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public a = async () => {
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await b();
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}
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}
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class A {
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public a = async () => {
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~~~~~ [Functions marked async must contain an await or return statement.]
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b();
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}
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}
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class A {
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public a = async () => 1;
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}
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async () => {
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await a();
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class A {
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async b() {
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~~~~~ [Functions marked async must contain an await or return statement.]
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console.log(1);
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}
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}
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};
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async function a() {
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let b = 1;
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return b;
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}
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let a = async () => 1;
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async function a() {
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~~~~~ [Functions marked async must contain an await or return statement.]
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let b = 1;
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let a = () => {
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return 1;
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}
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}
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async function foo;
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~~~~~ [Functions marked async must contain an await or return statement.]
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function * foo() {
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return 1;
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}
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[0]: Functions marked async must contain an await or return statement.

‎test/rules/no-async-without-await/tslint.json

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{
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"rules": {
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"no-async-without-await": true
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}
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}

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