Fix: getTokenAfter was wrong

[mysticatea]

What is the purpose of this pull request? (put an "X" next to item)

[X] Bug fix (template)

Tell us about your environment

• ESLint Version: master
• Node Version: 7.3.0
• npm Version: 3.8.9

What parser (default, Babel-ESLint, etc.) are you using?

• default

Please show your full configuration:

• nothing

What did you do? Please include the actual source code causing the issue.

I traversed tokens and comments by token = sourceCode.getTokenAfter(token, { includeComments: true }).

(function(a, /*b,*/ c){})

What did you expect to happen?

• It traverses 11 tokens.

What actually happened? Please include the actual, raw output from ESLint.

• It traverses 10 tokens (c is lost).

What changes did you make? (Give an overview)

This PR makes correct usage of indexMap (the map from locations to indices).

The map includes 2 kind of mapping; "token's locations to token's indices" and "comment's locations to token's indices". In the former case, it points itself index of each token. In the latter case, it points the next token's index of each comment. So it required additional checks in utils.getFirstIndex and utils.getLastIndex.

This PR fixes those, and adds tests for some edge cases.

Is there anything you'd like reviewers to focus on?

Nothing in particular.

[mention-bot]

@mysticatea, thanks for your PR! By analyzing the history of the files in this pull request, we identified @btmills, @not-an-aardvark and @nzakas to be potential reviewers.

[eslintbot]

LGTM

[eslintbot]

LGTM

[mysticatea]

I updated this PR and this PR's description.
It's ready to review.

[gyandeeps]

I would update the commit message to be more descriptive

[kaicataldo]

I agree with @gyandeeps about the commit message, but otherwise LGTM. Thanks!

[kaicataldo]

I think we should land this before our next release - it would be nice not to release this in a patch afterwards since we know there's a bug and it hasn't been used out in the wild yet.

[platinumazure]

I agree the commit message needs to be a bit more detailed. I don't mind if some of the details are in the commit message body (i.e., not in the first line shown in our release notes).

[not-an-aardvark]

I just ran into this issue. 😕

I'm blocked by this issue at the moment, so I'm going to merge it and update the commit message myself.