Input

const AppWrapper = <Options = any,>({
  appName,
}: {
  appName: string;
}) => null;

const getProps = <T = Record<string, unknown>,>(
  option: T | undefined,
): Partial<T> => ({});

Config

{
  "trailingComma": "es5"
}

Oxfmt output

Oxfmt version: 0.44.0

const AppWrapper = <Options = any>({ appName }: { appName: string }) => null;

const getProps = <T = Record<string, unknown>>(
  option: T | undefined
): Partial<T> => ({});

Oxfmt playground link

https://playground.oxc.rs/?t=formatter&formatterPanels=output,prettier&code=const%20AppWrapper%20%3D%20%3COptions%20%3D%20any%2C%3E%28%7B%0A%20%20appName%2C%0A%7D%3A%20%7B%0A%20%20appName%3A%20string%3B%0A%7D%29%20%3D%3E%20null%3B%0A%0Aconst%20getProps%20%3D%20%3CT%20%3D%20Record%3Cstring%2C%20unknown%3E%2C%3E%28%0A%20%20option%3A%20T%20%7C%20undefined%2C%0A%29%3A%20Partial%3CT%3E%20%3D%3E%20%28%7B%7D%29%3B

Prettier output

Prettier version: 3.8.1

const AppWrapper = <Options = any,>({ appName }: { appName: string }) => null;

const getProps = <T = Record<string, unknown>,>(
  option: T | undefined,
): Partial<T> => ({});

Additional notes

oxfmt removes the trailing comma from single-parameter generic type arguments in .tsx files (e.g. <Options = any,> becomes <Options = any>).

Prettier preserves the trailing comma in this position. The trailing comma convention exists in .tsx files to disambiguate <T> from a JSX opening tag — while the = default already provides disambiguation here, Prettier consistently preserves the comma regardless.

With trailingComma: "es5", both formatters should produce the same output. This difference was found while migrating a codebase from Prettier to oxfmt.