Add typings for typescript users.

[rictic]

No description provided.

[jsf-clabot]

All committers have signed the CLA.

[rictic]

This may be slightly unexpected, but it's a small dependency (28K on disk) and it includes all of the info needed to understand estree in typescript.

These estree typings combine well with typescript's type system, allowing for some really neat stuff. e.g. there's automatic type inference based on comparison with the type property. So typescript can type check this code correctly without any type annotations:

const program = espree.parse('foo');
const firstStatement = program.body[0];
if (firstStatement && firstStatement.type === 'ExpressionStatement') {
  const expression = firstStatement.expression;
  if (expression.type === 'Identifier') {
    console.log(expression.name);
    // typescript warns here, because an estree Identifier doesn't have a nom property
    console.log(expression.nom); 
  }
}

[nzakas]

I'm sorry, we aren't going to be including TypeScript definitions in the package. We just don't have the resources to maintain this on an ongoing basis, and we don't want to get into a situation where we then need to support type definitions for multiple dialects.

[rictic]

That's understandable. It's not much less convenient to have the types in DefinitelyTyped instead. Thanks for the quick review :)

[JounQin]

@rictic So are you going to add it into DefinitelyTyped?

[linonetwo]

@rictic Could you upload this to DefinitelyTyped? That will save many people.