Expected style "zIndex: 1px" to be unitless

[wu0407]

Bug report

Description / Observed Behavior

The Zindex in style has no unit, but the warning in the console is "Expected style "zIndex: 1px" to be unitless".
I try to set Zindex as int or string, it has the same result in the console under debug mode.

Expected Behavior

no warning

Reproduction

<div
      style={{
        display: "flex",
        flexDirection: "column",
        alignItems: "center",
        justifyContent: "center",
        // gap: "32px",
        padding: "20px 30px",
        width: "1349.5px",
        height: "390px",
        position: "relative",
        zIndex: 1,
        overflow: "hidden",
      }}
    >

Additional Context

satori: 0.20.0
nextjs: 15.1.2

[erxclau]

There was a similar issue regarding line height here: #535. Satori lists out CSS properties that should opt out of pixel units:

satori/src/handler/expand.ts

Lines 20 to 31 in 57a89ea

	const optOutPx = new Set([
	'flex',
	'flexGrow',
	'flexShrink',
	'flexBasis',
	'fontWeight',
	'lineHeight',
	'opacity',
	'scale',
	'scaleX',
	'scaleY',
	])

In theory, we could add zIndex to that list.

That said, setting a z-index has no effect because it is not supported in SVG, as mentioned in the README:

There is no z-index support in SVG. Elements that come later in the document will be painted on top.

The warning is a bit of a red herring since setting z-index doesn't do anything.