Is it bad practice to make a `Modifier` function that is `@Composable`?

# compose

[eygraber]

Is it bad practice to make a Modifier function that is @Composable?

[jw]

As opposed to Modifier.composed?

[Zach Klippenstein (he/him) [MOD]]

Generally I would try to avoid it because it usually indicates that you’re trying to do something in the wrong way. But I’m not sure we officially recommend against it

[eygraber]

The use case is that I migrated placeholder to Modifier.Node but the material version of it wraps the call in composed so it could use material properties

composed {
  Modifier.placeholder(
    visible = visible,
    color = if(color.isSpecified) color else PlaceholderDefaults.color(),
    shape = shape ?: MaterialTheme.shapes.small,
    highlight = highlight,
    placeholderFadeAnimationSpec = placeholderFadeAnimationSpec,
    contentFadeAnimationSpec = contentFadeAnimationSpec,
  )
}

It just felt weird to use composed after migrating away from it.

[Zach Klippenstein (he/him) [MOD]]

That might be a good reason. Also, consider filing a feature request to Material. If they just used composition locals directly, for example, you could access them from a modifier node.

[Ben Trengrove [G]]

The catch with using a composable function to return a modifier, rather than Modifier.composed, is that composition locals are resolved where the modifier is created, not used.

So for example if you have a modifier that uses a local called LocalColor and use it like this, it won't have the correct colour at the call site

val modifier = Modifier.myComposableModifier()
CompositionLocalProvider(LocalColor provides Green) {
   Box(modifier) // not green
}

[eygraber]

Is there an official recommendation then? There's a commit in the api guidelines that says that Modifier.composed is now discouraged. Does that mean generally discouraged, but should be used in certain scenarios, or does it mean "don't use it"?

[Ben Trengrove [G]]

We are still working it out, especially for your case where you are just looking up theming values. You can keep using composed for now or use a composable function