Babel plugin: Fixed bug when using + concatenation instead of a template literal

[mbrowne]

Summary

Currently, the Babel plugin successfully transpiles template literals, but doesn't work when building a string using +. i.e. this works:

import(`my-lib/${componentId}`)

But this does not:

import('my-lib/' + componentId)

The latter fails with an error:

TypeError: Property value expected type of string but got null

This PR fixes this issue by checking to see if the import expression is a BinaryExpression. I'm not sure if there are any other types of expressions that should be checked for, but this solves the issue for BinaryExpressions at least.

Test plan

I added a new test to verify that it works and also tested it in a real app.

[theKashey]

👍

[gregberge]

Thanks!