[Quarto] using reactive in Dashboards in Shiny for Python throws error

[karangattu]

When using this code to add reactivity when a button is clicked inside a Quarto document

@reactive.Effect
@reactive.event(input.reset)
def reset():

it throws an error

AttributeError: 'function' object has no attribute 'reset'

Quarto version: 1.4.530
Shiny for python version: 0.6.1.9000

[cpsievert]

Is your code block intentionally missing a function body for def reset(): ? If so, I don't think we'd expect that to work anyway (you'd need to add pass or ... to get a function that does nothing)?

[wch]

@cpsievert I believe this issue is specifically when Shiny is used in Quarto. (I think I know why it's not able to access input.reset at page render time.)

[gadenbuie]

This was just re-reported by a user on Discord: https://discord.com/channels/1109483223987277844/1214520904189612094/1214520904189612094.

[wch]

We will have a fix for this in Quarto soon. In the meantime, there is a workaround.

If this is the code:

@reactive.effect
@reactive.event(input.go)
def do_something():
    # Code that does stuff here ...

You can change it to this:

@reactive.effect
def do_something():
    input.go()
    with isolate():
        # Code that does stuff here ...

Using input.go() there causes do_something() to take a reactive dependency on it, so when the value of input.go() changes, it causes that effect to invalidate and re-execute. Then the with isolate() makes it so code inside that block does not cause an invalidation and re-execution.

In some cases it is also be useful to put the input.go() in a req(), as in:

@reactive.effect
def do_something():
    req(input.go())
    with isolate():
        # Code that does stuff here ...

This makes it so the if the value is falsy, (like None or 0), then it will stop execution there and not run the rest of the function.