feat(Subscription): Subscription now implements `Symbol.dispose` #7305

benlesh · 2023-07-12T12:10:02Z

Just an initial pass at implementing Symbol.dispose. Theoretical usage would be something like:

async function someLongRunningThing() {
  let valueFromObservable;

  // This is the usage.
  using someObservable$.subscribe(value => {
    valueFromObservable = value;
  })

  let n = 0;
  while (n++ < 10) {
    const userInput = await userInput();
    console.log(userInput + valueFromObservable);
  }

  // when this exits, the subscription will be "disposed".
}

cc @rbuckton

Related #7299

spec/helpers/interop-helper.ts

jakovljevic-mladen · 2023-07-12T14:32:20Z

src/internal/Subscription.ts

+// Even though Subscriptoin only conditionally implements `Symbol.dispose`
+// if it's available, we still need to declare it here so that TypeScript
+// knows that it exists on the prototype when it is available.
+export interface Subscription {


We should probably move this interface to types.ts file (either being merged with the existing Subscription interface or added as a new one like here) so it's in one place altogether. Also, maybe documentation could be added as well.

I have reasons I put it here actually:

Because I'm literally doing this to extend the Subscription interface.

I'm planning on a PR to move everything required in Observable to a single file (until I can split packages up)

I thought we already had Subscription interface, but we have SubscriptionLike which is not this one.

jakovljevic-mladen · 2023-07-12T14:33:20Z

src/internal/Subscription.ts

 function execFinalizer(finalizer: Unsubscribable | (() => void)) {
  if (isFunction(finalizer)) {
    finalizer();
  } else {
    finalizer.unsubscribe();
  }
 }
+
+// Ensure that `Symbol.dispose` is defined in TypeScript
+declare global {


How about this one being moved to types.ts file as well? Having it all in one place is better for maintaining.

Same as above. Also I suspect this will be removed in soon-released versions of TypeScript

If I'm not wrong, it will be added in 5.2 (next release), as they are also adding support for using. Merged a few weeks ago microsoft/TypeScript#54505

Source code of disposable interfaces: https://github.com/microsoft/TypeScript/blob/main/src/lib/esnext.disposable.d.ts#L7

jakovljevic-mladen · 2023-07-24T13:48:15Z

src/internal/Subscription.ts

+// Even though Subscriptoin only conditionally implements `Symbol.dispose`
+// if it's available, we still need to declare it here so that TypeScript
+// knows that it exists on the prototype when it is available.
+export interface Subscription {


I thought we already had Subscription interface, but we have SubscriptionLike which is not this one.

src/internal/Subscription.ts

Co-authored-by: Mladen Jakovljević <[email protected]>

niklas-wortmann

LGTM, pretty cool stuff!

benlesh commented Jul 12, 2023

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spec/helpers/interop-helper.ts Show resolved Hide resolved

jakovljevic-mladen reviewed Jul 12, 2023

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feat(Subscription): Subscription now implements Symbol.dispose

653528c

benlesh force-pushed the Symbol-dispose branch from c45b915 to 653528c Compare July 12, 2023 14:40

jakovljevic-mladen approved these changes Jul 24, 2023

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Update src/internal/Subscription.ts

537d328

Co-authored-by: Mladen Jakovljević <[email protected]>

niklas-wortmann approved these changes Aug 17, 2023

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benlesh merged commit 9bb0341 into ReactiveX:master Aug 18, 2023
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feat(Subscription): Subscription now implements `Symbol.dispose` #7305

feat(Subscription): Subscription now implements `Symbol.dispose` #7305

benlesh commented Jul 12, 2023 •

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feat(Subscription): Subscription now implements Symbol.dispose #7305

feat(Subscription): Subscription now implements Symbol.dispose #7305

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feat(Subscription): Subscription now implements `Symbol.dispose` #7305

feat(Subscription): Subscription now implements `Symbol.dispose` #7305

benlesh commented Jul 12, 2023 •

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benlesh Jul 12, 2023 •

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