Why is there no phx-value binding that takes an expression

Phoenix Forum Questions / Help
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Using JS.push we can send arbitrary values (only atoms seem to be converted to string).

<div phx-click={JS.push("signal", value: %{...}}>

Why can’t we just do that with phx-value?

<div phx-click="signal" phx-value={...}>
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I believe the values have to be json-encodable.

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phx-value will be encoded as an attribute and therefore will use HTML encoding rules. Via JS it is JSON based.

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I understand, that this is the way it is, but I find myself always using JS.push just to not have to convert everything from strings, so I’d like to have the simplicity of phx-value with the power of push/value.

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I agree, I see no reason why it couldn’t work this way. It would be a nice addition IMO.

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As it is, you’d have to implement Phoenix.HTML.Safe for Map, which would impact things outside of attributes (good or bad). Unsure how painful it would be to alter the heex engine to handle expression attributes in a special way vs other content.

The click handler also wont know if you’re trying to send the string "{}" or the JSON object {}, (or worse "{true: false}" where you meant to send json but encoded it wrong), so you probably also have to attach some metadata there to flag it as json when sending on the JS side, I guess by the heex engine attaching an additional attribute when its passed a non-string result. That intertwines heex and phx-value-* attributes pretty tightly though, don’t think there exists any heex extension system atm? Though recent changes to support xml (and so make it configurable?) probably means you could write your own small shim and just call up to the normal engine.

phx-json-value-x could be the way to go or maybe a specific JS.to_value(%{}) with some defined encoding patterns for LV to recognise. Neither are particularly appealing to me.

I would probably look to writing my own handler, that matched say soup-click="x", which grabbed all soup-click-value-x (or even phx-value-x) and json decoded them then pushEvent’d.

Currently I don’t think you can pushEvent on the raw socket, you need a hook so it can push to the correct parent view and you’d need to bind new elements in the updated callback.

Thats all a lot of work to avoid calling push though. I do prefer the attribute syntax.

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