Fix: no-useless-escape wrong loc and fix with CRLF in template elements

[mdjermanovic]

Prerequisites checklist

• I have read the contributing guidelines.

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

[ ] Documentation update
[x] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofixing to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

Tell us about your environment

• ESLint Version: v7.16.0
• Node Version: v12.18.4
• npm Version: v6.14.6

What parser (default, @babel/eslint-parser, @typescript-eslint/parser, etc.) are you using?

default

Please show your full configuration:

Configuration

module.exports = {
  parserOptions: {
    ecmaVersion: 2015
  }
};

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

With CRLF linebreaks:

/* eslint no-useless-escape: error */

`multiline template
literal with useless \escape`

What did you expect to happen?

1 error with the location of \.

Suggestions should remove \, or replace it with \\.

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

  4:21  error  Unnecessary escape character: \e  no-useless-escape

Location is wrong, editor underlines space before \.

Suggestion fixes are also wrong. The "remove" suggestion fixes the code to:

/* eslint no-useless-escape: error */

`multiline template
literal with useless\escape`

The "replace" suggestion fixes the code to:

/* eslint no-useless-escape: error */

`multiline template
literal with useless\ \escape`

What changes did you make? (Give an overview)

Replaced node.value.raw with sourceCode.getText(node) for TemplateElement nodes.

The rule assumed that TemplateElement#value.raw represents source code of the TemplateElement, similar to Literal#raw, but it's actually the Template Raw Value (TRV in the spec), the value that tag functions are getting as "raw".

It's usually the same as the source code, but there's at least one difference: CR and CRLF are normalized to LF.

The TRV of LineTerminatorSequence :: <CR> is the String value consisting of the code unit 0x000A (LINE FEED).
The TRV of LineTerminatorSequence :: <CR> <LF> is the String value consisting of the code unit 0x000A (LINE FEED).

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

The regex will now run on the full source code of strings and template elements, incl. quotes, backticks, ${ and }. I think that slicing the inner content is unnecessary and probably less efficient.

[aladdin-add]

LGTM! 💯