[BUG]: Violin box.line.color disappears after Plotly.restyle, but initial render shows it

Führe zunächst die bereitgestellte Python-Reproduktion mit Plotly Express, pio.to_html, Plotly.restyle und Playwright aus und vergleiche anschließend die beiden Screenshots. Verfolge den Violin-Trace bei fig.data[2] und das generierte HTML, um zu ermitteln, warum sich box.line.color vor und nach restyle unterscheidet. Als erledigt gilt die Aufgabe, wenn die rote eingebettete Box-Umrandung in beiden Fällen konsistent gerendert wird und eine Regressionstestabdeckung für die gemeldete Sequenz vorhanden ist.

Description

A Plotly Express scatter plot with marginal violins renders differently depending on
when box.line.color is applied to one violin trace.

If fig.data[2].box.line.color = "red" is set before the first render, the red box
outline inside the blue violin is visible. If the same base figure is rendered first
and the same value is applied later with Plotly.restyle, the red outline is missing.

Screenshots/Video

Steps to reproduce

import io

import plotly
import plotly.express as px
import plotly.io as pio
from PIL import Image, ImageChops
from playwright.sync_api import sync_playwright

print(f"Plotly version: {plotly.__version__}")

df = px.data.iris()
fig = px.scatter(
    df,
    x="sepal_width",
    y="sepal_length",
    color="species",
    marginal_y="violin",
    marginal_x="box",
    trendline="ols",
    template="simple_white",
)

# plot1.png: set the violin embedded box line color before the first render.
fig.data[2].box.line.color = "red"
assert fig.data[2].box.line.color == "red"
html1 = pio.to_html(fig, full_html=True, include_plotlyjs="cdn")

# plot2.png: render first, then apply the same value with Plotly.restyle.
fig.data[2].box.line.color = None
html2 = pio.to_html(fig, full_html=True, include_plotlyjs="cdn")
html2 = html2.replace(
    "</body>",
    """
<script>
window.addEventListener("DOMContentLoaded", () => {
    const plotEl = document.getElementsByClassName("plotly-graph-div")[0];
    setTimeout(() => {
        Plotly.restyle(plotEl, {"box.line.color": "red"}, [2]);
    }, 1000);
});
</script>
</body>""",
)

with sync_playwright() as playwright:
    browser = playwright.chromium.launch(
        headless=True,
        args=["--no-sandbox", "--disable-dev-shm-usage", "--disable-gpu"],
    )
    page = browser.new_page(viewport={"width": 1200, "height": 800})

    page.set_content(html1)
    page.wait_for_timeout(1500)
    img1 = page.screenshot(path="plot1.png")

    page.set_content(html2)
    page.wait_for_timeout(2000)
    img2 = page.screenshot(path="plot2.png")

    browser.close()

diff = ImageChops.difference(
    Image.open(io.BytesIO(img1)).convert("RGB"),
    Image.open(io.BytesIO(img2)).convert("RGB"),
)
assert diff.getbbox() is not None, "Screenshots are unexpectedly identical."
print("Saved plot1.png and plot2.png")

Notes

Add info here that doesn't fit in the other sections.