implab/implabjs-djx Commit - r142:894b8239b953

code review, minor refactoring

cin -

r142:894b8239b953 v1.9.0-rc5 default

parent child

Context file:

r142:894b8239b953

Collapse all files

djx/src/main/ts/observable.ts +32 -24

                  /**
                   * Called for the next element in the sequence
                   */
-                 next?: (value: T) => void;
+                 next?(value: T): void;
                  /**
                   * Called once when the error occurs in the sequence.
                   */
-                 error?: (e: unknown) => void;
+                 error?(e: unknown): void;
                  /**
                   * Called once at the end of the sequence.
                   */
-                 complete?: () => void;
+                 complete?(): void;
              }
              /**
              export type Producer<T> = (sink: Sink<T>) => (void | (() => void));
+             type FusedSink<T> = Omit<Sink<T>, "isClosed">;
+             type FusedProducer<T> = (sink: FusedSink<T>) => (void | (() => void));
              export interface Unsubscribable {
                  unsubscribe(): void;
              }
              const errorFallback = (e: unknown) => trace.error("Unhandled observable error: {0}", e);
              const sink = <T>(consumer: Observer<T>) => {
+                 // eslint-disable-next-line @typescript-eslint/unbound-method
                  const { next, error, complete } = consumer;
                  return {
                      next: next ? next.bind(consumer) : noop,
-                     error: error ? error.bind(consumer) : errorFallback,
-                     complete: complete ? complete.bind(consumer) : noop,
-                     isClosed: () => false
+                     error: error ? error.bind(consumer) : errorFallback, // report unhandled errors
+                     complete: complete ? complete.bind(consumer) : noop
                  };
              };
              /** Wraps the producer to handle tear down logic and subscription management
               *
+              * The resulting producer will invoke cleanup logic on error or complete events
+              * and will prevent calling of any method from the sink.
+              *
               * @param producer The producer to wrap
               * @returns The wrapper producer
               */
-             const fuse = <T>(producer: Producer<T>) => ({ next, error, complete }: Sink<T>) => {
+             const fuse = <T>(producer: Producer<T>) => ({ next, error, complete }: FusedSink<T>) => {
                  let done = false;
                  let cleanup = noop;
                      complete: _fin(complete),
                      isClosed: () => done
                  };
+                 // call the producer
                  cleanup = producer(safeSink) ?? noop;
+                 // if the producer throws exception bypass it to the caller rather then to
+                 // the sink. This is a feature.
+                 // if the producer completed the sequence immediately call the cleanup in place
                  return done ? cleanup() : _fin0;
              };
-             const _observe = <T>(producer: Producer<T>): Observable<T> => ({
+             const _observe = <T>(producer: FusedProducer<T>): Observable<T> => ({
                  subscribe: (consumer: Observer<T>) => ({
                      unsubscribe: producer(sink(consumer)) ?? noop
                  }),
                      }
                  }),
-                 reduce: <A>(...args: [AccumulatorFn<T, A>, A] | [AccumulatorFn<T, T>]) => _observe<T | A>(({ next, complete, error, ...rest }) => {
+                 reduce: <A>(...args: [AccumulatorFn<T, A>, A] | [AccumulatorFn<T, T>]) => _observe<T | A>(({ next, complete, error }) => {
                      if (args.length === 1) {
                          const [accumulator] = args;
                          let _acc: T;
                                      complete();
                                  }
                              },
-                             error,
-                             ...rest
+                             error
                          });
                      } else {
                          const [accumulator, initial] = args;
                                  next(_acc);
                                  complete();
                              },
-                             error,
-                             ...rest
+                             error
                          });
                      }
                  }),
                  next: collect(
                      producer,
-                     ({ next, complete, error, isClosed }) => ({
+                     ({ next, complete, error }) => ({
                          next: v => (next(v), complete()),
                          complete: () => error(new Error("The sequence is empty")),
-                         error,
-                         isClosed
+                         error
                      })
                  ),
                  collect: collect(
                      producer,
-                     ({ next, complete, ...rest }) => {
+                     ({ next, complete, error}) => {
                          const data: T[] = [];
                          return {
                              next: v => data.push(v),
                              complete: () => (next(data), complete()),
-                             ...rest
+                             error
                          };
                      }
                  )
              });
              const collect = <T, U>(
-                 producer: Producer<T>,
-                 collector: (result: Sink<U>) => Sink<T>
+                 producer: FusedProducer<T>,
+                 collector: (result: FusedSink<U>) => FusedSink<T>
              ) => (ct = Cancellation.none) => new Promise<U>((resolve, reject) => {
                  const fused = fuse<U>(({ next, complete, error, isClosed }) => {
                      const h = ct.register(error);
                      const cleanup = !isClosed() ?
-                         producer(collector({ next, complete, error, isClosed })) ?? noop :
+                         producer(collector({ next, complete, error })) ?? noop :
                          noop;
                      return () => {
                  fused({
                      next: resolve,
                      error: reject,
-                     complete: noop,
-                     isClosed: () => false
+                     complete: noop
                  });
              });
              /** Converts a subscribable to the observable */
              export const ofSubscribable = <T>(subscribable: Subscribable<T>) =>
-                 observe(sink => {
+                 observe<T>(sink => {
                      const subscription = subscribable.subscribe(sink);
                      return () => subscription.unsubscribe();
                  });

djx/src/main/ts/operators/subject.ts +18 -8

              const noop = () => { };
-             /** Joins multiple subscribers to the single one. The resulting subscriber
+             /** Connects multiple subscribers to the single producer. The producer
               * will be created when the first client subscribes and will be released
               * with the the last client unsubscribed.
               *
               * Use this wrapper to prevent spawning multiple producers.
               *
+              * The emitted values are not cached therefore the new subscriber will not receive
+              * the values emitted before it has been subscribed.
+              *
               * @param source The source observable
-              * @returns The wrapped producer
+              * @returns The new observable
               */
              export const subject = <T>(source: Subscribable<T>): Observable<T> => {
-                 let subscribers: Sink<T>[] = [];
+                 let subscribers: Sink<T>[] = []; // the list of active subscribers
-                 let subscription = { unsubscribe: noop };
+                 let subscription = { unsubscribe: noop }; // current subscription
                  // cleanup method to release resources held by this subscription
                  const cleanup = (cb: (item: Sink<T>) => void) => {
                      const _subscribers = subscribers;
-                     subscribers = [];
+                     subscribers = []; // this will prevent a client cleanup login to run
                      _subscribers.forEach(cb);
-                     subscription.unsubscribe();
+                     // we don't need subscription.unsubscribe(), because cleanup is called
+                     // from complete or error methods.
                  };
                  const sink: Sink<T> = {
                  return observe(client => {
                      const _subscribers = subscribers;
                      subscribers.push(client);
-                     if (subscribers.length === 1)
-                         subscription = source.subscribe(sink);
+                     if (subscribers.length === 1) // this is the first client
+                         subscription = source.subscribe(sink); // activate the producer
                      return () => {
+                         // this is a cleanup logic for an individual client
                          if (_subscribers === subscribers) {
+                             // is the current subscription to the producer is active
+                             // find this client in the list of subscribers
                              const pos = subscribers.indexOf(client);
                              if (pos >= 0)
                                  subscribers.splice(pos, 1);
+                             // is this is the last subscriber we need to release the producer
                              if (!subscribers.length)
                                  subscription.unsubscribe();
                          }

General Comments 0

Write
Preview

You need to be logged in to leave comments. Login now

No TODOs yet

	Site-wide shortcuts
/	Use quick search box
g h	Goto home page
g g	Goto my private gists page
g G	Goto my public gists page
g 0-9	Goto bookmarked items from 0-9
n r	New repository page
n g	New gist page

	Repositories
g s	Goto summary page
g c	Goto changelog page
g f	Goto files page
g F	Goto files page with file search activated
g p	Goto pull requests page
g o	Goto repository settings
g O	Goto repository access permissions settings
t s	Toggle sidebar on some pages