Undeclared variables being assigned when used with preset env targeting ES5

i-like-robots commented 5 years ago

When using the babel-plugin-transform-async-to-promises along with @babel/preset-env targeting an ES5 environment (such as IE 11) variables can be assigned without first being declared which causes the following error/s:

ReferenceError: assignment to undeclared variable varname

I have created a minimum test case demonstrating this issue here: https://github.com/i-like-robots/broken-babel-async-await-transform-test-case

There appears to be several ways to mitigate the issue as manifested in the example above:

Change the target to an ES6 compatible environment so that the variable declarations to not need transforming to use var syntax (not an option for us)
Move the export default statement to another line (most practical but in our case would require changes to number of code bases across our projects)
Avoid using certain variables within the scope of a function generated by this plugin (probably not possible)

This may be a duplicate of #38

rpetrich commented 5 years ago

Babel's scope tracking got more strict in babel 7.6 and broke the tracking of variables across functions; this is now remedied in master and will be in the next release.

i-like-robots commented 5 years ago

Thank you @rpetrich 👍

rpetrich / babel-plugin-transform-async-to-promises

Undeclared variables being assigned when used with preset env targeting ES5 #45