Start and end locations when there are decorators

[Joachim Seminck]

I am not really sure if this is actually a bug, or if it is working as intended. It causes a bug on another project (astexplorer) but before trying to find a way to deal with it there I first want to confirm here if it's a bug or working as intended.

I have seen that when a decorator is attached to an exported class, then the start and end locations of the ExportDefaultDeclaration are not updated correctly. There was a PR recently that fixes the locations on the node that the decorator is attached to, but it did not update any possible parent nodes.

Input Code

@connect(
  state => ({
    myElement: getMyElement(state)
  }), 
  { myAction }
)
export default class MyComponent extends React.Component {
  render() {}
}

Expected Behavior

Current Behavior

So if you look at the AST below, we can see that:

Program starts at 0
ExportDefaultDeclaration starts at 83
ClassDeclaration starts at 0 (actually this was done in #699 but ASTExplorer hasn't been updated yet)
Decorator starts at 0

So the question is: should ExportDefaultDeclaration start at 83 or at 0 ?

I have briefly looked into the code based on the existing PR. But in the code where we reset the start location for the ClassDeclaration, there seems to be no possible way to also update all the parents of that specific node. I'm not very well versed with parsers but I suppose that makes sense... there's only the object creations going on.

Anyway, if this is a bug I would really like to help out and fix it. If it is not a bug, then I'll look for an alternative solution to fix the bug that this causes in ASTExplorer: fkling/astexplorer#269

[Henry]

Hey @jseminck! We really appreciate you taking the time to report an issue. The collaborators
on this project attempt to help as many people as possible, but we're a limited number of volunteers,
so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack
community that typically always has someone willing to help. You can sign-up here
for an invite.

[Babel Bot]

This issue has been moved to babel/babel#6676.