Either all code paths should have explicit returns, or none of them JS-0045
Anti-pattern
Minor
5 months ago
—
5 months old
Async function 'sendMessage' expected no return value
393 return;
394 }
395
396 return await sendData(getHost(), getPort(), JSON.stringify(composeMessage(editor)));397}
398
399export function sendCommand(command: string): Promise<{Expected to return a value at the end of async function
39 .then(function () {
40 console.log(`Package updated: ${repo}`);
41 })
42 .catch(async function (err: { message: unknown }) { 43 vscode.window.showWarningMessage(
44 `Failed to download package from GitHub: ${err.message}. Fallback on local zip.`
45 );
Description
Any code paths that do not have explicit returns will return undefined.
It is recommended to replace any implicit dead-ends that return undefined with a return null statement.
As a convention, undefined signals that an unexpected value has been produced as the
result of a logical error in the program.
A null return, on the other hand, signals that the input to a function was incorrect,
or a value was 'not found'.
Having this distinction in code helps you figure out if something was caused because of a logical error, or malformed input to a function call.
Bad Practice
function getUser(name) {
if (userExists(name)) {
return userDb.get(name);
}
// whoops! Implicit undefined return
}
function readFile(fileName) {
if (fs.existsSync(fileName)) {
return fs.readFileSync(fileName, 'utf-8');
}
return; // Implicit undefined return.
}
Recommended
function getUser(name) {
if (userExists(name)) {
return userDb.get(name);
}
// `null` indicates there is no such user.
return null;
}
function readFile(fileName) {
if (fs.existsSync(fileName)) {
return fs.readFileSync(fileName, 'utf-8');
}
// `null` indicates there is no such file.
return null;
}