Move to yarn instead of npm

[cammellos]

User Story

As a developer,
I would like to use yarn instead of npm,
because it's faster (in our case) and does not get stuck installing packages

Description

We agreed to move to yarn instead of npm.

We tried to do so but failed as we were not able to build a release in a reasonable amount of time.

Moving to yarn is a trivial code change, but after:
lein prod-build

and

cd android && ./gradlew assembleRelease

it would take a very long time to create the artifact, around 6 hrs on my local machine ( compared to 6 minutes when installing packages through npm).

This has been replicated locally, on docker and on the macos build server.

The steps that fails is app:bundleReleaseJsAndAssets.

We see jest-worker hogging the CPU at 100%, memory consumption is also quite high, once it actually failed because the node engine could not allocate memory.

A few scattered thoughts that might help

There are a few issues (some closed) facebook/react-native#11696 which seems to indicate that it's bundling files that it should not be (realm files for example).

Some people mentioned .babelrc was the culprit, but did not elaborate any further.

What we tried, but did not work

Increase node memory from 4GB to 8GB
Increase gradlew memory from 1GB to 4GB
Add ___tests__ to inputExcludes in android/app/react.gradle
Decrease the number of jest-workers

Currently we don't have the bandwidth to look into this any further, but if anyone wants to have a go at this it would be helpful.

[andytudhope]

@dbalatero got quite far with this before getting busy with his own work. Do you have any thoughts?

References:
#2541
#2649

[cammellos]

thanks @andytudhope
#2541 is not an issue anymore, as we don't use rn-nodeify anymore I believe
#2649 seems the same issue I believe, only happens on android

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[jeluard]

Closing for now as it appears moving to yarn is not practical for us.

[jeluard]

@alwx Can you share the gist of your findings?