chore: Setup tslib & importHelpers to improve bundle size

[jimblanc]

Description of changes

This change enables importHelpers in our shared build script (build.js) and adds tslib as a dependency to all packages that use the script to improve bundle size.

Note on methodology

I collected the data below by looking at the minified WebPack bundle files that each of our modules produce. While this may not reflect all use-cases, it provides a readily available & consistent metric to evaluate the impact of the change. As far as dependency de-duping & flattening for more complex apps, the numbers below should capture the worst-case where each package includes the minimum number of tslib dependencies that it requires without any additional de-duping that the importing app may perform.

Package	Artifact	Before Change	After Change	Bundle Δ
aws-amplify	aws-amplify.min.js	1294 KiB	1294 KiB	0 KiB
analytics	aws-amplify-analytics.min.js	296 KiB	285 KiB	-11 KiB
api	aws-amplify-api.min.js	146 KiB	145 KiB	-1 KiB
api-graphql	aws-amplify-api-graphql.min.js	144 KiB	142 KiB	-2 KiB
api-rest	aws-amplify-api-rest.min.js	43 KiB	41 KiB	-2 KiB
auth	aws-amplify-auth.min.js	157 KiB	155 KiB	-2 KiB
cache	aws-amplify-cache.min.js	15.5 KiB	15.7 KiB	+0.2 KiB
core	aws-amplify-core.min.js	290 KiB	281 KiB	-9 KiB
datastore	aws-amplify-datastore.min.js	617 KiB	590 KiB	-27 KiB
datastore-storage-adapter	aws-amplify-datastore-sqlite-adapter-expo.min.js, aws-amplify-datastore-storage-adapter.min.js	47.6 KiB	44.9 KiB	-2.7 KiB
geo	aws-amplify-geo.min.js	218 KiB	216 KiB	-2 KiB
interactions	aws-amplify-interactions.min.js	323 KiB	315 KiB	-8 KiB
predictions	aws-amplify-predictions.min.js	556 KiB	556 KiB	0 KiB
storage	aws-amplify-storage.min.js	328 KiB	322 KiB	-6 KiB
xr	aws-amplify-xr.min.js	14.7 KiB	13.6 KiB	-1.1 KiB

Total Δ for entire project -73.6 KiB

Note Soon-to-be deprecated UI packages, as well as the pushnotification package (which is not used for web & does not use the shared build script) were not included in this change.

Future improvements

• Refactor build.js so that each package can have its own tsconfig.json
  • This will allow us to disable importHelpers for packages where it doesn't provide any benefit such as cache
• Upgrade packages that depend on older (< 2.0.0) versions of tslib to improve dependency flattening, for example:
  • @aws-crypto/sha256-js
  • @aws-sdk/credential-provider-cognito-identity
  • @aws-sdk/client-cognito-identity

Issue #, if available

NA

Description of how you validated changes

• Local release build & unit test pass
• Manually evaluated WebPack'd bundle sizes

Integ test pass on next-major-version/5: https://app.circleci.com/pipelines/github/aws-amplify/amplify-js/15155/workflows/3a454e6b-c4e8-47aa-9190-359b225d4ffd

• Existing storage failures already present

Checklist

• PR description included
• yarn test passes
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[manueliglesias]

LGTM!

[manueliglesias]

Is this related to tslib?

[jimblanc]

So from what I can tell this is kind of a known issue with Jest & TypeScript because babel will only include getters for re-exported functions (like browserOrNode in this file). I'm not entirely sure why this was working before though. I double checked the TS configuration and experimented with setting importHelpers through the ts-jest configuration but it didn't seem to affect anything one way or the other.