feat: make watch$ strictNullCheck compatible (#34)

* feat: make `watch$` strictNullCheck compatible

* chore: send initial value to subscribers

* let values emit when undefined

* fix: properly check if data can be processed

Co-authored-by: Lucy Cifferello <12953208+elvece@users.noreply.github.com>

client/lib/json-patch-lib.ts

@@ -75,7 +75,7 @@ function recursiveApply<T extends Record<string, T>> (data: T, path: readonly st
 }
 
 function isObject (val: any): val is Record<string, unknown> {
-  return typeof val === 'object' && !Array.isArray(val) && val !== null
+  return typeof val === 'object' && val !== null
 }
 
 function jsonPathToKeyArray (path: string): string[] {

client/lib/store.ts

@@ -1,5 +1,5 @@
 import { DBCache, Dump, Http, Revision, Update } from './types'
-import { BehaviorSubject, Observable } from 'rxjs'
+import { BehaviorSubject, Observable, ReplaySubject } from 'rxjs'
 import { applyOperation, getValueByPointer, Operation } from './json-patch-lib'
 import BTree from 'sorted-btree'
 
@@ -11,10 +11,10 @@ export interface StashEntry {
 export class Store<T extends { [key: string]: any }> {
   cache: DBCache<T>
   sequence$: BehaviorSubject<number>
-  private watchedNodes: { [path: string]: BehaviorSubject<any> } = { }
+  private watchedNodes: { [path: string]: ReplaySubject<any> } = {}
   private stash = new BTree<number, StashEntry>()
 
-  constructor (
+  constructor(
     private readonly http: Http<T>,
     private readonly initialCache: DBCache<T>,
   ) {
@@ -22,22 +22,23 @@ export class Store<T extends { [key: string]: any }> {
     this.sequence$ = new BehaviorSubject(initialCache.sequence)
   }
 
-  watch$ (): Observable<T>
+  watch$(): Observable<T>
-  watch$<P1 extends keyof T> (p1: P1): Observable<T[P1]>
+  watch$<P1 extends keyof T>(p1: P1): Observable<NonNullable<T[P1]>>
-  watch$<P1 extends keyof T, P2 extends keyof T[P1]> (p1: P1, p2: P2): Observable<T[P1][P2]>
+  watch$<P1 extends keyof T, P2 extends keyof NonNullable<T[P1]>>(p1: P1, p2: P2): Observable<NonNullable<NonNullable<T[P1]>[P2]>>
-  watch$<P1 extends keyof T, P2 extends keyof T[P1], P3 extends keyof T[P1][P2]> (p1: P1, p2: P2, p3: P3): Observable<T[P1][P2][P3]>
+  watch$<P1 extends keyof T, P2 extends keyof NonNullable<T[P1]>, P3 extends keyof NonNullable<NonNullable<T[P1]>[P2]>>(p1: P1, p2: P2, p3: P3): Observable<NonNullable<NonNullable<NonNullable<T[P1]>[P2]>[P3]>>
-  watch$<P1 extends keyof T, P2 extends keyof T[P1], P3 extends keyof T[P1][P2], P4 extends keyof T[P1][P2][P3]> (p1: P1, p2: P2, p3: P3, p4: P4): Observable<T[P1][P2][P3][P4]>
+  watch$<P1 extends keyof T, P2 extends keyof NonNullable<T[P1]>, P3 extends keyof NonNullable<NonNullable<T[P1]>[P2]>, P4 extends keyof NonNullable<NonNullable<NonNullable<T[P1]>[P2]>[P3]>>(p1: P1, p2: P2, p3: P3, p4: P4): Observable<NonNullable<NonNullable<NonNullable<NonNullable<T[P1]>[P2]>[P3]>[P4]>>
-  watch$<P1 extends keyof T, P2 extends keyof T[P1], P3 extends keyof T[P1][P2], P4 extends keyof T[P1][P2][P3], P5 extends keyof T[P1][P2][P3][P4]> (p1: P1, p2: P2, p3: P3, p4: P4, p5: P5): Observable<T[P1][P2][P3][P4][P5]>
+  watch$<P1 extends keyof T, P2 extends keyof NonNullable<T[P1]>, P3 extends keyof NonNullable<NonNullable<T[P1]>[P2]>, P4 extends keyof NonNullable<NonNullable<NonNullable<T[P1]>[P2]>[P3]>, P5 extends keyof NonNullable<NonNullable<NonNullable<NonNullable<T[P1]>[P2]>[P3]>[P4]>>(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5): Observable<NonNullable<NonNullable<NonNullable<NonNullable<NonNullable<T[P1]>[P2]>[P3]>[P4]>[P5]>>
-  watch$<P1 extends keyof T, P2 extends keyof T[P1], P3 extends keyof T[P1][P2], P4 extends keyof T[P1][P2][P3], P5 extends keyof T[P1][P2][P3][P4], P6 extends keyof T[P1][P2][P3][P4][P5]> (p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6): Observable<T[P1][P2][P3][P4][P5][P6]>
+  watch$<P1 extends keyof T, P2 extends keyof NonNullable<T[P1]>, P3 extends keyof NonNullable<NonNullable<T[P1]>[P2]>, P4 extends keyof NonNullable<NonNullable<NonNullable<T[P1]>[P2]>[P3]>, P5 extends keyof NonNullable<NonNullable<NonNullable<NonNullable<T[P1]>[P2]>[P3]>[P4]>, P6 extends keyof NonNullable<NonNullable<NonNullable<NonNullable<NonNullable<T[P1]>[P2]>[P3]>[P4]>[P5]>>(p1: P1, p2: P2, p3: P3, p4: P4, p5: P5, p6: P6): Observable<NonNullable<NonNullable<NonNullable<NonNullable<NonNullable<NonNullable<T[P1]>[P2]>[P3]>[P4]>[P5]>[P6]>>
-  watch$ (...args: (string | number)[]): Observable<any> {
+  watch$(...args: (string | number)[]): Observable<any> {
     const path = `/${args.join('/')}`
     if (!this.watchedNodes[path]) {
-      this.watchedNodes[path] = new BehaviorSubject(getValueByPointer(this.cache.data, path))
+      this.watchedNodes[path] = new ReplaySubject(1)
+      this.updateValue(path)
     }
     return this.watchedNodes[path].asObservable()
   }
 
-  update (update: Update<T>): void {
+  update(update: Update<T>): void {
     if (this.isRevision(update)) {
       // if old or known, return
       if (update.id <= this.cache.sequence || this.stash.get(update.id)) return
@@ -47,18 +48,24 @@ export class Store<T extends { [key: string]: any }> {
     }
   }
 
-  reset (): void {
+  reset(): void {
     Object.values(this.watchedNodes).forEach(node => node.complete())
-    this.watchedNodes = { }
+    this.watchedNodes = {}
     this.stash.clear()
     this.sequence$.next(0)
     this.cache = {
       sequence: 0,
-      data: { } as any,
+      data: {} as any,
     }
   }
 
-  private handleRevision (revision: Revision): void {
+  private updateValue(path: string): void {
+    const value = getValueByPointer(this.cache.data, path)
+
+    this.watchedNodes[path].next(value)
+  }
+
+  private handleRevision(revision: Revision): void {
     // stash the revision
     this.stash.set(revision.id, { revision, undo: [] })
 
@@ -70,7 +77,7 @@ export class Store<T extends { [key: string]: any }> {
     this.processStashed(revision.id)
   }
 
-  private handleDump ({ value, id }: Dump<T>): void {
+  private handleDump({ value, id }: Dump<T>): void {
     this.cache.data = { ...value }
     this.stash.deleteRange(this.cache.sequence, id, false)
     this.updateWatchedNodes('')
@@ -78,12 +85,12 @@ export class Store<T extends { [key: string]: any }> {
     this.processStashed(id + 1)
   }
 
-  private processStashed (id: number): void {
+  private processStashed(id: number): void {
     this.undoRevisions(id)
     this.applyRevisions(id)
   }
 
-  private undoRevisions (id: number): void {
+  private undoRevisions(id: number): void {
     let stashEntry = this.stash.get(this.stash.maxKey() as number)
 
     while (stashEntry && stashEntry.revision.id > id) {
@@ -92,7 +99,7 @@ export class Store<T extends { [key: string]: any }> {
     }
   }
 
-  private applyRevisions (id: number): void {
+  private applyRevisions(id: number): void {
     let revision = this.stash.get(id)?.revision
     while (revision) {
       let undo: Operation<unknown>[] = []
@@ -129,7 +136,7 @@ export class Store<T extends { [key: string]: any }> {
     this.stash.deleteRange(0, this.cache.sequence, false)
   }
 
-  private updateWatchedNodes (revisionPath: string) {
+  private updateWatchedNodes(revisionPath: string) {
     const kill = (path: string) => {
       this.watchedNodes[path].complete()
       delete this.watchedNodes[path]
@@ -139,18 +146,17 @@ export class Store<T extends { [key: string]: any }> {
       if (this.watchedNodes[path].observers.length === 0) return kill(path)
 
       if (path.includes(revisionPath) || revisionPath.includes(path)) {
-        const val = getValueByPointer(this.cache.data, path)
+        this.updateValue(path)
-        this.watchedNodes[path].next(val)
       }
     })
   }
 
-  private updateSequence (sequence: number): void {
+  private updateSequence(sequence: number): void {
     this.cache.sequence = sequence
     this.sequence$.next(sequence)
   }
 
-  private isRevision (update: Update<T>): update is Revision {
+  private isRevision(update: Update<T>): update is Revision {
     return 'patch' in update
   }
 }