When users see errors like
```
Duplicate plugin/preset detected.
If you'd like to use two separate instances of a plugin,
they need separate names, e.g.
plugins: [
['some-plugin', {}],
['some-plugin', {}, 'some unique name'],
]
```
It can be difficult to determine the source of the conflict, especially
in a larger build system.
This commit outputs what is known about the plugins that actually
conflict, which can be helpful for users to determine the root cause of
the conflict.
Partially addresses #9778
* Fixed null error in plugin opts and added a test for it
* Remove !opts and add opts === null check to avoid confusion with false and undefined cases
Co-Authored-By: divbhasin <divbest99@gmail.com>
* Enable babel for tests
This enables babel for tests by using a mocha compiler
It uses the babel config from package.json
Transformed OptionsManager test to es2015 to see if it works
Removed the 5s timeout from cli tests, as the default timeout is already 10s, this should probably fix the timouts on travis that we had in babylon
Also run the cli tests on travis, they were disabled if istanbul active, but istanbul is always active on travis so we were never running this tests.
* ignore scripts directory
* only register for tests
* Set only flag correctly
