Report '\08' and '\09' in no-octal-escape

[mdjermanovic]

Tell us about your environment

• ESLint Version: 6.1.0
• Node Version: 10.16.0
• npm Version: 6.9.0

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

default

Please show your full configuration:

Configuration

```js
module.exports = {
  parserOptions: {
    ecmaVersion: 2015,
  },
};

What did you do? Please include the actual source code causing the issue, as well as the command that you used to run ESLint.

/*eslint no-octal-escape: "error"*/

"\08"
"\09"

eslint index.js

What did you expect to happen?

2 errors

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

No errors

Are you willing to submit a pull request to fix this bug?

Yes, I'll be glad to do it. (#12079 should be merged first as this would collide)

Engines/parsers are already reporting these as octal escapes in strict mode:

"use strict";
"\08"

• Chrome: Octal escape sequences are not allowed in strict mode.
• Firefox: "0"-prefixed octal literals and octal escape sequences are deprecated; for octal literals use the "0o" prefix instead
• Espree: Octal literal in strict mode

Per the spec. 08 is not a valid escape sequence but it seems that it can be interpreted like 0 as a LegacyOctalEscapeSequence followed by a character 8.

LegacyOctalEscapeSequence::

OctalDigit[lookahead ∉ OctalDigit]

So I guess to be technically correct the rule should report \0?

[eslint-deprecated]

Unfortunately, it looks like there wasn't enough interest from the team
or community to implement this change. While we wish we'd be able to
accommodate everyone's requests, we do need to prioritize. We've found
that issues failing to reach accepted status after 21 days tend to
never be accepted, and as such, we close those issues.
This doesn't mean the idea isn't interesting or useful, just that it's
not something the team can commit to.

Thanks for contributing to ESLint and we appreciate your understanding.

[mdjermanovic]

Reopening because it's probably a false negative.

[kaicataldo]

Marking this as accepted since it's a bug report with three 👍s

[mdjermanovic]

Looks like no one is working on this, so I'll take it.