Feature request: no-describe-context

[quiqueg]

Do you want to request a feature or report a bug?
Feature

What is the current behavior?
The no-describe-variables rule prevents developers from creating variables inside describe blocks, instead encouraging them to make use of Jasmine's user context feature (this inside before*, it, and after*). However, developers may not know that the user context feature doesn't work inside describe blocks, so they may try to do something like this:

describe('my test', function () {
  this.incorrectUse = 'of UserContext';

  it('uses UserContext incorrectly', function () {
    // ...
  });
});

Not only is this incorrect, it is dangerous, as the context of describe blocks is the Jasmine Suite object itself. Setting a property on this object may interfere with Jasmine's internals (e.g., setting this.result will overwrite the test results, setting this.id changes the id of the suite, etc.).

What is the expected behavior?
An eslint-plugin-jasmine rule called no-describe-context should prevent this behavior. Detect and warn about usage of this directly inside describe blocks (probably only for un-bound / non-arrow functions).