effect feat(Stream): switchMap

Type

[ ] Refactor
[x] Feature
[ ] Bug Fix
[ ] Optimization
[ ] Documentation Update

Description

Name	Type
effect	Minor
@effect/cli	Major
@effect/cluster-browser	Major
@effect/cluster-node	Major
@effect/cluster-workflow	Major
@effect/cluster	Major
@effect/experimental	Major
@effect/opentelemetry	Major
@effect/platform-browser	Major
@effect/platform-bun	Major
@effect/platform-node-shared	Major
@effect/platform-node	Major
@effect/platform	Major
@effect/printer-ansi	Major
@effect/printer	Major
@effect/rpc-http	Major
@effect/rpc	Major
@effect/schema	Major
@effect/sql-d1	Major
@effect/sql-drizzle	Major
@effect/sql-kysely	Major
@effect/sql-mssql	Major
@effect/sql-mysql2	Major
@effect/sql-pg	Major
@effect/sql-sqlite-bun	Major
@effect/sql-sqlite-node	Major
@effect/sql-sqlite-react-native	Major
@effect/sql-sqlite-wasm	Major
@effect/sql	Major
@effect/typeclass	Major
@effect/vitest	Major

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Jun 10 '24 16:06 changeset-bot[bot]

What is the benefit over flatMap(f, { switch: true })?

Jun 11 '24 22:06 tim-smart

I guess just verbosity, not sure if this is common enough to justify it

Jun 12 '24 09:06 mikearnaldi

RxJS also do have a switchMap operator, and it's one of the most important and widely used operator.

I decided to make it as a separate operator not just because of verbosity, but because of clarity and visualization.

This is a real code from my project

export const BinanceWsUnitSingleLayer = Layer.effect(
  BinanceWsUnitTag,
  Effect.gen(function* () {
    // ....................................................................
    return {
      createStream(
        stream: string,
      ): Stream.Stream<
        unknown,
        | BinanceWsConnectionError
        | BinanceWsResponseError
        | BinanceWsConnectionCloseError
      > {
        return Stream.suspend(() => {
          debug(`📤Requesting stream "${stream}"`);
          let stream$ = streams.get(stream);
          if (stream$) {
            return stream$;
          }
          stream$ = connection.pipe(
            Stream.flatMap(
              (ws) =>
                Effect.request(
                  BinanceWsSubscribeRequest({ stream, ws }),
                  RequestResolver.contextFromEffect(subscribe),
                ).pipe(
                  Stream.unwrap,
                  Stream.ensuring(
                    Effect.gen(function* () {
                      debug(`🔻 Unsubscribing ${stream}`);
                      streams.delete(stream);
                      yield* Effect.request(
                        BinanceWsUnsubscribeRequest({ stream, ws }),
                        RequestResolver.contextFromEffect(unsubscribe),
                      );
                    }),
                  ),
                ),
              { switch: true, concurrency: 1 },
            ),
          );
          streams.set(stream, stream$);
          return stream$;
        });
      },
    } satisfies BinanceWsUnit;
  }),
)

When you fluently read this code, it is not really easy to notice the options parameter for flatMap, you only see Stream.flatMap, but default flatMap behaviour is different. In addition, there are no clear documentation about what does switch option means. On the site it is written

if the order of concatenation is not important for us, we can use the switch option.

And it doesn't describes this concept.

Actually, i thinks that the switch option changes the behaviour dramatically enough to extract it to the separate operator with it's own documentation and example, which i also provided in this PR.

Jun 12 '24 09:06 dilame

@tim-smart what should we do? I am kind of in favour of accepting this given the semantic specificity

Jun 17 '24 12:06 mikearnaldi

@tim-smart what should we do? I am kind of in favour of accepting this given the semantic specificity

I think we can add it back as flatMapSwitch (what it was called before we consolidated the apis).

We would then mark the switch option as depreciated and remove it in 4.0?

Jun 18 '24 09:06 tim-smart

@dilame can you pls fix the version in since to 3.5 and I'll merge it

Jun 22 '24 12:06 mikearnaldi

@mikearnaldi done

Jun 23 '24 21:06 dilame

/rebase

Jul 12 '24 15:07 dilame

@dilame can you pls fix the version in since to 3.5 and I'll merge it

Hi! Just wanted to remind that i changed the version in since that time to 3.5.0 and just now i changed it to 3.6.0 😃

Jul 17 '24 16:07 dilame

feat(Stream): switchMap

Type

Description

Related

🦋 Changeset detected