Unnecessary new lines injected by typescript parser.

Prettier 1.19.1 Playground link

--parser typescript
--print-width 120

Input:

export const Foo = forwardRef((props: FooProps, ref: Ref<HTMLElement>): JSX.Element => {
  return <div />;
});

export const Bar = forwardRef((props: BarProps, ref: Ref<HTMLElement>): JSX.Element | null => {
  return <div />;
});

users.map((user: User): User => {
  return user;
})

Output:

export const Foo = forwardRef(
  (props: FooProps, ref: Ref<HTMLElement>): JSX.Element => {
    return <div />;
  }
);

export const Bar = forwardRef((props: BarProps, ref: Ref<HTMLElement>): JSX.Element | null => {
  return <div />;
});

users.map(
  (user: User): User => {
    return user;
  }
);

Expected behavior: Prettier leaves the code as is.

This formatting issue only occurs when using the typescript parser. If you switch over to the babel parser, the code remains untouched.

The extra lines that prettier injects seem overkill, especially for the users.map example.

It’s interesting though how that functions that have a union return type, don’t get rewritten to a new line.

[whitneyit]

If this is considered a bug, I would be happy to work on a fix

[whitneyit]

~I’m keen to work on it as well. I’m not sure if it is deemed a bug or not 🤷‍♂️~

I didn’t see the label come through via email 🤦‍♂️