Don't leave blank lines when no-unused-variable autofix removes whole import

[pablonete]

PR checklist

• Addresses an existing issue: no-unused-variables autofix leaves empty lines #2898
• New enhancement
  • Includes tests

Overview of change:

When an unused import is deleted, the line break is removed too.
Unless there are more sentences in the same line, so the break is preserved.

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

• Can you think on other scenarios we need to cover?
• This is my first time contributing to TSLint and consuming TS compiler API. Let me know if there's something that can be improved.

CHANGELOG.md entry:

"[enhancement] no-unused-variable: Don't leave empty lines when import is removed"

[palantirtech]

Thanks for your interest in palantir/tslint, @pablonete! Before we can accept your pull request, you need to sign our contributor license agreement - just visit https://cla.palantir.com/ and follow the instructions. Once you sign, I'll automatically update this pull request.

[ajafff]

that will only work if you're using \n. if there's \r\n, it will only remove \r

alternative to end++:

const nextLine = ctx.sourceFile.getLineAndCharacterOfPosition(end).line + 1;
const lineStarts = ctx.sourceFile.getLineStarts();
if (lineStarts.length !== nextLine) {
    end = lineStarts[nextLine];
}

[pablonete]

Nice suggestion, done!

[adidahiya]

thanks @pablonete!