fix: invalid operator in operator-assignment messages

[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 autofix to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

Tell us about your environment:

• ESLint Version: v8.12.0
• Node Version: 16.14.0
• npm Version: 8.3.1

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.

Online Demo

/* eslint operator-assignment: ["error", "never"] */

a += b;

What did you expect to happen?

One operator-assignment error with a correct message.

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

One operator-assignment error with an incorrect message.

3:1  error  Unexpected operator assignment (+==) shorthand  operator-assignment

(note extra = in +==)

What changes did you make? (Give an overview)

Removed = from meta messages, updated the code for "always" to pass in the expected operator instead of adding = in the message, and updated all "invalid" tests to check data.

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

[nzakas]

LGTM