Feature: Analyze @throws tags

Description

Given a function has a @throws JSDoc tag, it would be helpful to apply some analysis and raise a compiler warning (or, if configured, an error) when the caller does not handle the error and it doesn’t declare its own @throws tag.

Examples

/**
 * @throws {SomeException}
 */
function myFunction() {
  // some logic
  // then for some reason we throw an exception
  if (somethingWentWrong) {
    throw new SomeException("something happened");
  }
  // some more logic
}

function potentialMess() {
  myFunction(); // Compiler error: 'myFunction' may throw `SomeException`. ts(9876)
}

/**
 * @throws {SomeException}
 */
function letItBubble() {
  myFunction(); // No compiler errors
}

function aFunctionThatHandlesTheException() {
  try {
    myFunction(); // No compiler errors
  }
  catch (error) {
    // do something with the error
  }
}

Questions

• Ideally, it would be even better if VSCode realizes that myFunction throws an error, and then @throws is not required for the analysis. Still, this approach would be useful when dealing with external code/interfaces.

• It is my understanding that JSDoc’s @throws is allowed once – if this is correct, then VSCode could ignore this and accept multiple tags anyway? Otherwise, maybe we can use a different tag, e.g. @exception?

[kitsonk]

A potential compromise is for JS, that @throws is evaluated as a function that returns never of which, there is a level of checking built in to ensure that such a function doesn’t return a value.

[jhpratt]

For what it’s worth, I’d very much like some sort of indicator that a function can throw. I just tried extracting out a common “unexpected state” throw, and realized that I can’t do so safely because TS lacks this functionality.