Trigger onReady callback on resubscribe

[zimme]

This fixes #1173.

Tests needs updating. I know what needs updating,
I just need to update commends and stuff before
committing.

[zimme]

This should be ready now.

[hwillson]

Thanks @zimme - this all looks great! I'm re-running the tests now, but assuming they pass we should be all set to get this merged.

[hwillson]

One question - do you think we need to worry about instances where people are counting on the current (buggy) behaviour? For example, #1173 (comment). If so this might be a breaking change.

[zimme]

I guess we might need a short discussion about if we want to keep the current behaviour and document that you can use handle.ready() if you want the behaviour that this PR brings instead.

However I do think this should be classified as a bug and fixed because there are more people that assume that this function would work the way it would with this PR applied.

So maybe a warning in History.md about a potential breaking change for people relying on this broken behaviour.

On another note, do we have any way of achieving what the developers in that comment were doing if we apply this patch?

[mitar]

I would vote for merging this in and adding a history entry.

[hwillson]

Thanks @mitar - that was the consensus on our triage call today as well (we were just waiting for the failed tests to re-run). This will be merged shortly (@abernix is planning on adding a small adjustment to the History.md to explain how this could break backwards compatibility in some cases).

[sebakerckhof]

Question: Why, in the case the existing subscription is not yet ready, is the ready callback overwritten instead of added? I mean the code has this comment:

 the semantics we provide is
// that at the time the sub first becomes ready, we call the last
// onReady callback provided, if any.`

But this doesn't really make sense if you think about a component-based GUI, since the onReady callback will often be used to for example hide a loading indicator.

So that means if you have 2 different components subscribing to the same thing more or less at the same time, and both use the 'onReady' callback to hide a loading indicator inside the component, only one will be called and thus one component will keep showing the loading indicator?

[zimme]

@sebakerckhof, even if 2 components were to subscribe to the same publication there would still be 2 separate subscription instances with their own onReady callbacks? So I don't think they would contaminate each other.

I believe this might be more related to conditionally calling subscribe for the same publication in an autorun with different callbacks based on the condition?

[sebakerckhof]

@zimme Yeah, nevermind, I missed the inactive part. I thought this code was to avoid sending the same subscription twice to the server, but it's about autorun behavior.

[benjamn]

Merged into Release 1.5.1 as part of 1.5.1-beta.3.