decorate - compose decorators for a single prop

[ramybenaroya]

PR checklist:

• Added unit tests
• Updated changelog
• Updated docs (either in the description of this PR as markdown, or as separate PR on the gh-pages branch. Please refer to this PR). For new functionality, at least API.md should be updated
• Added typescript typings
• Verified that there is no significant performance drop (npm run perf)

Changes

• Reduce multiple decorators to a single decorator
• Added a test for multiple decorators (@action + custom) on a function property
• Added a test for multiple decorators (@observable + @serializable) on
  a regular property
• Added a usage example (+ caveat warning) in readme under decorate section

Usage Example:

import { decorate, observable } from "mobx"
import { serializable, primitive } from "serializr"
import persist from 'mobx-persist';

class Todo {
    id = Math.random();
    title = "";
    finished = false;
}
decorate(Todo, {
    title: [serializable(primitive), persist('object'), observable],
    finished: observable
})

[ramybenaroya]

I added serializr as a dev dependency just for this test, so I can compose @observable with another decorator @serializable(primitive()).

[mweststrate]

N.P.

[ramybenaroya]

Not so sure if my explanation is clear enough. Would love to get a feedback about it.
After approval I'll open a gh-pages PR

[mweststrate]

Note: not all decorators can be composed together, and this functionality is just best-effort. Some decorators affect the instance directly and can 'hide' the effect of other decorators that only change the prototype

[coveralls]

Coverage increased (+0.02%) to 93.92% when pulling 2e07c95 on ramybenaroya:compose-property-decorators into f76f198 on mobxjs:master.

[mweststrate]

Please mension what the application order is. I assume serializable is applied first, then persist and finally observable?

[ramybenaroya]

correct

[mweststrate]

Some small comments, further looking great!
Note that if you need to support this feature for MobX, a second PR targeting mobx4-master should be opened.

Thanks!

[ramybenaroya]

Thanks for the feedback @mweststrate.

if you need to support this feature for MobX...

I didn't get what you meant by that. Can you elaborate about "support for MobX"?

[mweststrate]

@ramybenaroya sorry, meant MobX 4. In other words; master represents 5, but 4 is still maintained as well so it might be interesting to backport this one. (if this branch is merged with squash, it can probably just be cherry-picked)