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Streams `toString` / `valueOf` behaviour clashes with DOM diff early exit #2150

barneycarroll opened this Issue May 14, 2018 · 2 comments


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barneycarroll commented May 14, 2018

Thanks @cmnstmntmn for discovering this: streams semi-automatic string coercion behaviour conflicts with virtual DOM diffing algo, which will skip diffing a stream reference in place of a VDOM node. Here's an example: interpolating value without explicitly invoking it will ensure the text node forever stays at the initial value.

It was my idea to give streams toString behaviour, and in hindsight I think it was a terrible mistake: the effort saved through avoiding those parentheses unleashes a world of ambiguity. I had already convinced myself the original idea was conceptually bad in #2050, but this points to a problem caused by opinionated tolerance in many places - vnode normalisation should also be fixed to cater for the other end of this issue.


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pygy commented May 14, 2018

Oooh yeah, let's ditch that!


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spacejack commented May 15, 2018

Yeah I got burned similarly today. I had changed a boolean var into a stream, and in my view I had:

isCondition ? m('.foo) : m('.bar')

It's especially hazardous when refactoring things into streams. And Typescript can't do much with valueOf either so it won't help out.

barneycarroll added a commit that referenced this issue May 15, 2018

@pygy pygy closed this in e1a5089 May 15, 2018

@porsager porsager referenced this issue Sep 14, 2018


Rewrite stream #2207

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