TypeScript migration: @storybook/channels

[kroeder]

Issue: N/A

What I did

Migrated @storybook/channels to TypeScript

How to test

Tests are included - currently almost 100% coverage. Test for async: true is missing

[codecov]

Codecov Report

Merging #4977 into next will decrease coverage by 0.15%.
The diff coverage is 96.72%.

@@            Coverage Diff            @@
##             next   #4977      +/-   ##
=========================================
- Coverage   34.85%   34.7%   -0.16%     
=========================================
  Files         579     589      +10     
  Lines        7038    7262     +224     
  Branches      943     984      +41     
=========================================
+ Hits         2453    2520      +67     
- Misses       4082    4239     +157     
  Partials      503     503

Impacted Files	Coverage Δ
lib/channels/src/index.ts	96.72% <96.72%> (ø)
app/angular/src/client/preview/render.js	0% <0%> (ø)	⬆️
...pp/angular/src/client/preview/angular-polyfills.js
...client/preview/angular/components/app.component.ts	27.02% <0%> (ø)
addons/notes/src/index.ts	84.61% <0%> (ø)
app/angular/src/demo/button.component.ts	0% <0%> (ø)
app/angular/src/demo/welcome.component.ts	0% <0%> (ø)
.../storyshots-core/src/frameworks/angular/helpers.ts	0% <0%> (ø)
...shots-core/src/frameworks/angular/app.component.ts	0% <0%> (ø)
...p/angular/src/client/preview/angular/decorators.ts	100% <0%> (ø)
... and 7 more

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[kroeder]

Rewrote all tests in order to reflect the actual usage of this package
Before, there were lots of tests on private class members

Coverage is almost 100% - I don't know how to test async: true (see todo comment in the code)

Also, the whole package is type safe - no any usage except for generics as default value (that makes them optional)

[Keraito]

Awesome PR and work! Have some question regarding different aspects of TS and implementation. Would definitely like to help out with this! 😃

[Keraito]

Same goes for the from field similar to the type field, see comment above.

[ndelangen]

Yeah should be either manager or preview

[kroeder]

How can it be manager or preview if you check this

const event: ChannelEvent<TEventArgs[]> = { type: eventName, args, from: this.sender };

Where this.sender is

  private sender = generateRandomId();

and the function does

const generateRandomId = () => {
  // generates a random 13 character string
  return Math.random()
    .toString(16)
    .slice(2);
};

Either we rewrite some stuff or I can't do this:

  from: 'preview' | 'manager';

due to type checking errors (all hail typescript 😄 )

[ndelangen]

We need to NOT test this file:
examples/angular-cli/src/test

[ndelangen]

hmm

Number of tests 149 is 84% less than 913 in build #5452
[16:25:46]	Build failure condition: Anchor value for number of tests is taken from <latest successful build>. 
Fail build if number of tests is 20% less than the anchor value

and

ERR! FAILED to compile ts: @storybook/[email protected] 

[ndelangen]

Ready to merge?

[kroeder]

Ready to merge?

Yes, I still need feedback from you regarding the from property - see discussions!
Lets resolve this discussion, I might add a change and then we are ready to go!