From c8a47c9fb3adcf7b2f52ef069d26215097ead083 Mon Sep 17 00:00:00 2001
From: MarekSpodBiedry <73122968+MarekSpodBiedry@users.noreply.github.com>
Date: Mon, 12 Oct 2026 08:31:44 +0200
Subject: [PATCH] Read omitted val on chart smooth and showVal as on (#518)

---
 crates/xlsx/src/chart.rs                    |  4 +--
 crates/xlsx/src/tests/chart_bool_default.rs | 32 +++++++++++++++++++++
 crates/xlsx/src/tests/mod.rs                |  1 +
 3 files changed, 35 insertions(+), 2 deletions(-)
 create mode 100644 crates/xlsx/src/tests/chart_bool_default.rs

diff --git a/crates/xlsx/src/chart.rs b/crates/xlsx/src/chart.rs
index 052d620..020ce67 100644
--- a/crates/xlsx/src/chart.rs
+++ b/crates/xlsx/src/chart.rs
@@ -106,7 +106,7 @@ fn read_series(s: &El) -> Series {
         color,
         secondary: false,
         kind: None,
-        smooth: s.child("smooth").and_then(|e| e.attr("val")).and_then(|v| v.parse::<u8>().ok()).is_some_and(|v| v != 0),
+        smooth: bool_val(s, "smooth"),
         trendlines: s.kids("trendline").filter_map(read_trendline).collect(),
     }
 }
@@ -201,7 +201,7 @@ pub fn read_chart(root: &El) -> Option<Chart> {
         }
     }
     let kind = if groups.len() > 1 { ChartKind::Combo } else { first_kind };
-    let show_val = |e: &El| e.child("dLbls").and_then(|d| d.child_val("showVal")).is_some_and(|v| v == "1" || v == "true");
+    let show_val = |e: &El| e.child("dLbls").is_some_and(|d| bool_val(d, "showVal"));
     let data_labels = groups.iter().any(|(g, _)| show_val(g) || g.kids("ser").any(show_val));
     let val_axes: Vec<&El> = plot.kids("valAx").collect();
     let cat_ax = plot.child("catAx").or_else(|| plot.child("dateAx"));
diff --git a/crates/xlsx/src/tests/chart_bool_default.rs b/crates/xlsx/src/tests/chart_bool_default.rs
new file mode 100644
index 0000000..e9a074c
--- /dev/null
+++ b/crates/xlsx/src/tests/chart_bool_default.rs
@@ -0,0 +1,32 @@
+//! A `CT_Boolean` chart flag with no `val` attribute is on (ECMA-376), for series smoothing and value labels.
+
+use crate::chart::read_chart;
+use crate::xml::parse;
+
+/// Reads a line chart with `ser` appended to its one series and `group` inside the group's `<c:dLbls>`.
+fn flags(ser: &str, group: &str) -> (bool, bool) {
+    let xml = format!(
+        "<c:chartSpace xmlns:c=\"http://schemas.openxmlformats.org/drawingml/2006/chart\"><c:chart><c:plotArea><c:lineChart>\
+         <c:grouping val=\"standard\"/><c:ser><c:idx val=\"0\"/><c:order val=\"0\"/>\
+         <c:val><c:numRef><c:f>Data!$A$1:$A$5</c:f></c:numRef></c:val>{ser}</c:ser><c:dLbls>{group}</c:dLbls>\
+         <c:axId val=\"1\"/><c:axId val=\"2\"/></c:lineChart><c:catAx><c:axId val=\"1\"/></c:catAx><c:valAx><c:axId val=\"2\"/></c:valAx>\
+         </c:plotArea></c:chart></c:chartSpace>"
+    );
+    let root = parse(xml.as_bytes()).unwrap();
+    let ch = read_chart(&root).unwrap();
+    (ch.series[0].smooth, ch.data_labels)
+}
+
+#[test]
+fn omitted_val_means_on() {
+    assert_eq!(flags("<c:smooth/>", "<c:showVal/>"), (true, true));
+    assert_eq!(flags("<c:dLbls><c:showVal/></c:dLbls>", ""), (false, true), "series-level value labels");
+}
+
+#[test]
+fn explicit_values_are_honoured() {
+    assert_eq!(flags("<c:smooth val=\"1\"/>", "<c:showVal val=\"1\"/>"), (true, true));
+    assert_eq!(flags("<c:smooth val=\"true\"/>", "<c:showVal val=\"true\"/>"), (true, true));
+    assert_eq!(flags("<c:smooth val=\"0\"/>", "<c:showVal val=\"0\"/>"), (false, false));
+    assert_eq!(flags("", ""), (false, false));
+}
diff --git a/crates/xlsx/src/tests/mod.rs b/crates/xlsx/src/tests/mod.rs
index d5d2f2f..eef5d5f 100644
--- a/crates/xlsx/src/tests/mod.rs
+++ b/crates/xlsx/src/tests/mod.rs
@@ -1,6 +1,7 @@
 //! Integration-style tests: round trips, hand-written fixtures, hostile input and CSV.
 
 mod array_export;
+mod chart_bool_default;
 mod csv_tests;
 mod encrypted_tests;
 mod fixtures;