fix(store): state stream should always return latest value even if update is queued up

[arturovt]

In the current behavior the StateStream internal value (_value: T) is not set immediately since its updates are queued up due to the OrderedBehaviorSubject implementation we use. The BehaviorSubject#getValue() basically returns this._value which isn't deterministically returns latest values. This happens when one action is dispatched after another action synchronously and the last action is trying to update the state and get it immediately:

store.dispatch(new Action_1()).subscribe(() => {
  store.dispatch(new Action_2())
})

Let's say the Action_2 does the following:

action_2_handler(ctx, action) {
  ctx.patchState({ newValue: action.newValue });
  console.log(ctx.getState().newValue);
}

We would expect to see the newValue equal to action.newValue, but it will show the previous value. Because patchState update is queued up.

[bundlemon]

BundleMon

Files updated (1)

Status	Path	Size	Limits
✅	fesm2015/ngxs-store.js	94.34KB (+260B +0.27%)	125KB / +0.5%

Unchanged files (2)

Status	Path	Size	Limits
✅	fesm2015/ngxs-store-operators.js	6.23KB	15KB / +0.5%
✅	fesm2015/ngxs-store-internals.js	4.22KB	20KB / +0.5%

Total files change +260B +0.24%

Groups updated (3)

Status	Path	Size	Limits
✅	@ngxs/store(esm2015)[gzip] ./esm2015/**/*.js	181.33KB (+368B +0.2%)	+1%
✅	@ngxs/store(umd)[gzip] ./bundles/*.umd.js	36.63KB (+63B +0.17%)	+1%
✅	@ngxs/store(fesm2015)[gzip] ./fesm2015/*.js	25.09KB (+50B +0.19%)	+1%

Final result: ✅

View report in BundleMon website ➡️

---

Current branch size history | Target branch size history

[bundlemon]

BundleMon (NGXS Plugins)

Unchanged files (14)

Status	Path	Size	Limits
✅	Plugins(umd)[gzip] storage-plugin/bundles/ngxs-storage-plugin.um d.js	7.96KB	+1%
✅	Plugins(umd)[gzip] router-plugin/bundles/ngxs-router-plugin.umd. js	7.41KB	+1%
✅	Plugins(umd)[gzip] websocket-plugin/bundles/ngxs-websocket-plugi n.umd.js	6.92KB	+1%
✅	Plugins(umd)[gzip] hmr-plugin/bundles/ngxs-hmr-plugin.umd.js	6.89KB	+1%
✅	Plugins(fesm2015)[gzip] storage-plugin/fesm2015/ngxs-storage-plugin.j s	3.64KB	+1%
✅	Plugins(umd)[gzip] form-plugin/bundles/ngxs-form-plugin.umd.js	3.44KB	+1%
✅	Plugins(fesm2015)[gzip] router-plugin/fesm2015/ngxs-router-plugin.js	3.09KB	+1%
✅	Plugins(umd)[gzip] devtools-plugin/bundles/ngxs-devtools-plugin. umd.js	2.75KB	+1%
✅	Plugins(fesm2015)[gzip] form-plugin/fesm2015/ngxs-form-plugin.js	2.67KB	+1%
✅	Plugins(fesm2015)[gzip] hmr-plugin/fesm2015/ngxs-hmr-plugin.js	2.65KB	+1%
✅	Plugins(fesm2015)[gzip] websocket-plugin/fesm2015/ngxs-websocket-plug in.js	2.59KB	+1%
✅	Plugins(umd)[gzip] logger-plugin/bundles/ngxs-logger-plugin.umd. js	2.53KB	+1%
✅	Plugins(fesm2015)[gzip] devtools-plugin/fesm2015/ngxs-devtools-plugin .js	2.17KB	+1%
✅	Plugins(fesm2015)[gzip] logger-plugin/fesm2015/ngxs-logger-plugin.js	2.01KB	+1%

No change in files bundle size

Unchanged groups (3)

Status	Path	Size	Limits
✅	All Plugins(esm2015)[gzip] ./-plugin/esm2015/**/.js	108.71KB	+1%
✅	All Plugins(umd)[gzip] ./-plugin/bundles/.umd.js	37.91KB	+1%
✅	All Plugins(fesm2015)[gzip] ./-plugin/fesm2015/.js	18.82KB	+1%

Final result: ✅

View report in BundleMon website ➡️

---

Current branch size history | Target branch size history

[bundlemon]

BundleMon (Integration Projects)

Files updated (3)

Status	Path	Size	Limits
✅	Main bundles(Gzip) hello-world-ng13-ivy/dist-integration/main.(h ash).js	69.8KB (+50B +0.07%)	+1%
✅	Main bundles(Gzip) hello-world-ng14-ivy/dist-integration/main.(h ash).js	64.86KB (+39B +0.06%)	+1%
✅	Main bundles(Gzip) hello-world-ng12-ivy/dist-integration/main.(h ash).js	67.95KB (+36B +0.05%)	+1%

Total files change +125B +0.06%

Final result: ✅

View report in BundleMon website ➡️

---

Current branch size history | Target branch size history

[codeclimate]

Code Climate has analyzed commit 874e079 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 96.7% (0.0% change).

View more on Code Climate.