Flow comments import export

[lightsofapollo]

Q	A
Patch: Bug Fix?	yes
Major: Breaking Change?	no
Minor: New Feature?	no
Deprecations?	no
Spec Compliancy?	yes?
Tests Added/Pass?	yes
Fixed Tickets	Fixes #5538
License	MIT
Doc PR
Dependency Changes

While trying to get flow types working in relay-runtime I ran into this issue where babel-plugin-transform-flow-comments is not re-exporting types (export ... from ...).

Includes separate commit /w failing test if this fix is somehow not appropriate.

[mention-bot]

@lightsofapollo, thanks for your PR! By analyzing the history of the files in this pull request, we identified @hzoo, @danharper and @existentialism to be potential reviewers.

[babel-bot]

Hey @lightsofapollo! It looks like one or more of your builds have failed. I've copied the relevant info below to save you some time.

• Node vnode - linux

[codecov]

Codecov Report

Merging #5675 into 7.0 will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             7.0    #5675      +/-   ##
=========================================
+ Coverage   84.4%   84.42%   +0.02%     
=========================================
  Files        284      284              
  Lines       9749     9749              
  Branches    2733     2733              
=========================================
+ Hits        8229     8231       +2     
+ Misses      1008     1007       -1     
+ Partials     512      511       -1

Impacted Files	Coverage Δ
.../babel-plugin-transform-flow-comments/src/index.js	100% <100%> (+6.89%)	⬆️
packages/babel-helper-call-delegate/src/index.js	64% <0%> (-4%)	⬇️
packages/babel-traverse/src/path/modification.js	73.78% <0%> (-0.98%)	⬇️
...bel-plugin-transform-es2015-classes/src/vanilla.js	90.17% <0%> (ø)	⬆️
packages/babel-traverse/src/path/context.js	86.2% <0%> (+0.86%)	⬆️
packages/babel-traverse/src/visitors.js	86.66% <0%> (+0.95%)	⬆️

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[loganfsmyth]

I'm curious, have you explored going with .js.flow files instead? We've actually talked about deprecating this plugin since it seems like an ugly workflow in general.

[lightsofapollo]

@loganfsmyth For my own general use .flow works much better... In this case I am trying to "teach" relay-runtime (which I am not all that familiar /w) to output stuff which contains flow definitions (either .flow or comments).

graphql-js does this really easily by simply copy/pasting the src/ and changing .js to .js.flow... It works well there because the standard module system is being used (instead of @providesModule)...

This is the result of random debugging and hopefully is useful to someone else (even if I ultimately end up /w .flow implementation of relay-runtime)

[hzoo]

If anything we should move it out of this repo if someone else wants to maintain it since we'd like to deprecate. Other issues like #5600, and issues with classes etc have the similar issues

[hzoo]

Will merge but yeah we need to figure out what to do with the plugin (deprecate?)