Go To Definition doesn't work for certain module patterns

[klinquist]

@waderyan asked me to open up a bug in the TypeScript repo for my comment on this issue:
microsoft/vscode#15004

TypeScript Version: VSCode 1.7.1

Code

myfile.js:

module.exports = function(baseUrl){
  this.apiCall = function(url, cb) {
     let fullUrl = baseUrl + url;
  };

  return this;
}

Expected behavior:

If I let test = require('myfile')(baseUrl) then test.apiCall(url, cb), I should be able to 'go to definition' on apiCall.

Actual behavior:

Cannot go to definition.

[aluanhaddad]

You have to call new test.

[klinquist]

When not in strict mode, I don't have to return a new constructor for my script to work..

[aluanhaddad]

Irregardless you need to call the function.

[klinquist]

Sorry - I do call the function (I just updated my test code). Please try it - you'll see that Go To Definition does not work.

[aluanhaddad]

Indeed it does not work.
The following works as expected

module.exports = function (baseUrl) {
  return {
      apiCall: function (url, cb) {
        let fullUrl = baseUrl + url;
      }
  };
};

The issue is that this is typed as any throughout the original function. The actual value of this will vary at runtime depending on the context in which the code is called.

[klinquist]

Would a let self = this, then returning self make it work?

[mhegazy]

Would a let self = this, then returning self make it work?

no. the system currently does not track assignments to this as property declarations. i.e. this.apiCall is not treated as a declaration for a new property called apiCall on this. this is true if you alias this as well (self = this).

you could however, enhance the experience by using JSDoc comments:

/**
 *  @return {{apiCall: (url, cb)=> string;}}
 */
module.exports = function (baseUrl) {
...
}

[abgivant]

I use a similar module pattern in an application I'm working on, and the lack of IntelliSense/definitions for those has been an issue for me as well.

Mine follow this basic pattern:

module.exports = function(x, y, z) {
  var exports = {};
  exports.method = function() {
    // Something that might use x, y, or z
  };
  return exports;
}

Would it be possible to do something like include an option in the jsconfig.json file to specify a property name or list of names to track when determining module exports?

Maybe something like this?

{
  "moduleOptions": {
    "exportProperty": ["exports", "this"]
  }
}

[mhegazy]

@abgivant, this pattern is actually an easier one to support, we already have plans to do so on the future. it is a general construction patter that is common in JS.
the this one is a bit more tricky though.

[abgivant]

@mhegazy Ah cool. Is that part of the "expando" discussion, or is there a more specific feature in the works for things like that?

[waderyan]

Let's move the latter discussion to the new issue #12416