Add js2-declare-variable

[jacksonrayhamilton]

I have a little present for you: A new utility function, js2-declare-variable!

js2-declare-variable makes it easy to extend var statements. Bound to C-c C-v, just enter the name of a variable (and optionally its initial value) and js2-declare-variable will append the declaration to the first var statement in the scope enclosing point.

If there isn't already a var statement in the enclosing scope, one will be created.

If there is a "use strict" statement or comments at the top of the enclosing scope, the var statement will be inserted after them.

In implementing this, I discovered a bug in js2-node-get-enclosing-scope where a node without a parent would trigger an error, because js2-node-parent could not operate on nil. The new fuction requires js2-node-get-enclosing-scope to behave correctly, so I fixed it.

I also noticed #218 when writing the js2-declare-variable-comment-* tests, so I simply added an extra newline in those tests to prevent that particular error. I would rather they not be there, so I marked them with TODOs until that bug is fixed. (Update: e054673 and efdc5f6 fixed that.)

I have signed the copyright forms for Emacs and they have been approved; I guess that means I can legally contribute to this repository as well?

I hope you like this feature and thanks for your review.

[jacksonrayhamilton]

This PR now depends on #220.

[dgutov]

I can see quite a bit of effort went into this, but are you sure js2-mode is the best place for it, as opposed to js2-refactor? It implements a set of editing commands already, and this one might be a welcome addition.

I have signed the copyright forms for Emacs and they have been approved; I guess that means I can legally contribute to this repository as well?

It does. Magnar also signed it, so it probably means we could add js2-refactor to GNU ELPA without too much effort, in case that's your primary interest in contributing this command here.

[jacksonrayhamilton]

Seeing as #159 is pending I assumed this would be an okay place to put it.

I'd have to rewrite the tests, but if you think it belongs there, I can suggest it to the maintainer. We don't necessarily need to get the package on ELPA, do we? I can just as easily use MELPA.

[dgutov]

Seeing as #159 is pending I assumed this would be an okay place to put it.

That pull request is different: it's navigation, not editing. I don't think we actually have any editing commands here. And we add one, the other ones must follow, and then we'll start duplicating js2-refactor.

I'd have to rewrite the tests, but if you think it belongs there, I can suggest it to the maintainer.

Let's start with asking him. Maybe you won't have to rewrite the tests that much.

We don't necessarily need to get the package on ELPA, do we?

Sure, it's up to you. ELPA just means a wider audience.

[jacksonrayhamilton]

I've continued development of this feature in js2-refactor and the author seems interested. Thanks for pointing me in the right direction.