fix(parcats): use a parcats-specific ParcatsHoverInfo enum

Addresses roborev finding: Parcats.hover_info reused common::HoverInfo,
which cannot express parcats' valid values (count/probability) and offers
x/y/z/text/name that parcats ignores. Add ParcatsHoverInfo (count,
probability, count+probability, all, none, skip) matching the plotly.js
parcats hoverinfo flaglist.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: jqnatividad

CHANGELOG.md

@@ -26,7 +26,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/) a
 - [[#422](https://github.com/plotly/plotly.rs/issues/422)] Add `Icicle` trace type (hierarchical icicle chart; sibling of `Treemap`/`Sunburst`)
 - [[#422](https://github.com/plotly/plotly.rs/issues/422)] Add layout-level `uirevision` to preserve UI state (zoom/pan/selection) across re-renders (complements the trace-level `uirevision` added in #421)
 - Add `Splom` trace type (scatter-plot matrix) with `SplomDimension`/`SplomAxis`/`SplomDiagonal` config and `showupperhalf`/`showlowerhalf` controls
-- Add `Parcats` trace type (parallel categories) with `ParcatsDimension`/`ParcatsLine` config and `ParcatsLineShape`/`ParcatsArrangement`/`ParcatsHoverOn`/`ParcatsSortPaths` enums
+- Add `Parcats` trace type (parallel categories) with `ParcatsDimension`/`ParcatsLine` config and `ParcatsLineShape`/`ParcatsArrangement`/`ParcatsHoverOn`/`ParcatsSortPaths`/`ParcatsHoverInfo` enums
 
 ### Changed
 

plotly/src/traces/parcats.rs

@@ -5,7 +5,7 @@ use serde::Serialize;
 
 use crate::{
     color::Color,
-    common::{ColorScale, Dim, Domain, HoverInfo, PlotType},
+    common::{ColorScale, Dim, Domain, PlotType},
     layout::CategoryOrder,
     Trace,
 };
@@ -44,6 +44,22 @@ pub enum ParcatsSortPaths {
     Backward,
 }
 
+/// Determines which trace information appears on hover for a parcats trace.
+///
+/// Unlike the cartesian [`HoverInfo`](crate::common::HoverInfo), parcats hover
+/// info is limited to `count`/`probability` (plus `all`/`none`/`skip`).
+#[derive(Serialize, Clone, Debug)]
+#[serde(rename_all = "lowercase")]
+pub enum ParcatsHoverInfo {
+    Count,
+    Probability,
+    #[serde(rename = "count+probability")]
+    CountAndProbability,
+    All,
+    None,
+    Skip,
+}
+
 /// A single dimension (column) of a [`Parcats`] trace.
 #[serde_with::skip_serializing_none]
 #[derive(Serialize, Debug, Clone, FieldSetter)]
@@ -181,9 +197,10 @@ where
     // the more general form and is used here.
     #[serde(rename = "hovertemplate")]
     hover_template: Option<String>,
-    /// Determines which trace information appears on hover.
+    /// Determines which trace information appears on hover. Limited to
+    /// `count`/`probability` (plus `all`/`none`/`skip`).
     #[serde(rename = "hoverinfo")]
-    hover_info: Option<HoverInfo>,
+    hover_info: Option<ParcatsHoverInfo>,
     /// Sets the domain within which this parcats trace is drawn.
     domain: Option<Domain>,
 }
@@ -276,6 +293,23 @@ mod tests {
         assert_eq!(to_value(line).unwrap(), expected);
     }
 
+    #[test]
+    fn serialize_parcats_hover_info() {
+        assert_eq!(to_value(ParcatsHoverInfo::Count).unwrap(), json!("count"));
+        assert_eq!(
+            to_value(ParcatsHoverInfo::Probability).unwrap(),
+            json!("probability")
+        );
+        assert_eq!(
+            to_value(ParcatsHoverInfo::CountAndProbability).unwrap(),
+            json!("count+probability")
+        );
+        assert_eq!(to_value(ParcatsHoverInfo::Skip).unwrap(), json!("skip"));
+
+        let trace = Parcats::<i32>::new().hover_info(ParcatsHoverInfo::Count);
+        assert_eq!(to_value(trace).unwrap()["hoverinfo"], json!("count"));
+    }
+
     #[test]
     fn serialize_parcats_dimension() {
         let dim = ParcatsDimension::new()