fix rollup imports and sourcemap support(jest + rollup)

[jbaxleyiii]

Fixes #248

cc @evans

[evans]

@jbaxleyiii I added sourcemap support for jest coverage and rollup builds(wasn't picking up the tsc sourcemaps). Tested with example from #248, so should work 🙏. We should definitely think about moving to RxJs if they have addressed the bundle size issues

[apollo-cla]

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[codecov-io]

Codecov Report

Merging #489 into master will increase coverage by 4.36%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #489      +/-   ##
==========================================
+ Coverage    91.3%   95.67%   +4.36%     
==========================================
  Files          19       18       -1     
  Lines         828      601     -227     
  Branches      204      146      -58     
==========================================
- Hits          756      575     -181     
+ Misses         67       20      -47     
- Partials        5        6       +1

Impacted Files	Coverage Δ
packages/apollo-link/src/link.ts	90.19% <ø> (-2.54%)	⬇️
packages/apollo-link/src/test-utils/mockLink.ts	85.71% <ø> (+0.71%)	⬆️
packages/apollo-link/src/linkUtils.ts	97.67% <ø> (+8.63%)	⬆️
packages/apollo-link/src/test-utils/setContext.ts	87.5% <ø> (-2.98%)	⬇️
...ackages/apollo-link/src/test-utils/testingUtils.ts	100% <0%> (ø)	⬆️
packages/apollo-link-retry/src/retryFunction.ts	100% <0%> (ø)	⬆️
packages/apollo-link-retry/src/delayFunction.ts	100% <0%> (ø)	⬆️
... and 13 more

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[evans]

apollo-link's bundle now emits Observable = Observable && Observable.hasOwnProperty('default') ? Observable['default'] : Observable; and the index contains import Observable from 'zen-observable'; , so we should be set

[stefanoTron]

awesome! when will this be merged? 😊 thanks!

[jbaxleyiii]

@evans AMAZING

[evans]

@littletower We merged and published. Can you post in #389 if it still doesn't work with 1.2.0

[JounQin]

It breaks #511, and requires
adding allowSyntheticDefaultImports: true into tsconfig.json, is that reasonable to require specific tsconfig?

[evans]

@JounQin Good point! We shouldn't be forcing a specific tsconfig.json. I think the best way forward is to either switch to RxJs or write an implementation of zen-observable in typescript, since the * as imports break js builds and a direct import necessitates the allowSyntheticDefaultImports. Please take a look at #515. If you think there is a better way forward please share.