Run plugin also on Program:exit

[danez]

We have the usecase that one of our own transforms adds dynamic imports with paths which need to be replaced by this plugin.

This wasn't working because this plugin is run on Program:enter before all other plugins are executed.
I changed it so that the plugin now runs on both enter and exit to handle both of the usecases:

• Other plugin wants to resolve/use path to module from import/require (needs replacement happen before -> Program:enter)
• Other plugin inserts a new import/require (needs replacement happen afterwards -> Program:exit)

In order to avoid double transformation I added a list of already visited paths, so that each path only gets visited/transformed once.

[codecov]

Codecov Report

Merging #269 into master will not change coverage.
The diff coverage is 100%.

Impacted Files	Coverage Δ
src/transformers/call.js	100% <100%> (ø)	⬆️
src/index.js	100% <100%> (ø)	⬆️
src/transformers/import.js	100% <100%> (ø)	⬆️

[tleunen]

This looks very good to me. Thank you @danez.

cc @fatfisz

[fatfisz]

Hmm I'd be careful with this one - I vaguely remember a situation like this:

1. module-resolver changed the path
2. Another plugin replaced the node
3. module-resolver changed the path again because there was no info about it being already resolved (a completely new node was there)

I don't think going back to this behavior is good and it might bite us soon.