fix(forms): a literal Off value reads as Off outside buttons (#1320) (#1393)

The field reader dropped the value "Off" for every field kind, so a
text field, combo box or single-select list set to "Off" read as empty
and exported an empty value to CSV, text, XML, XFDF and FDF, although
the document stored it. "Off" is now treated as no value only for
check boxes and radio buttons, where it is the off state.

Adds tests::a_literal_off_value_reads_as_off_outside_buttons, which
fails before this change.

crates/forms/src/lib.rs

@@ -430,12 +430,14 @@ fn actions_of(doc: &Document, d: &Dict, widgets: &[ObjRef]) -> af::Actions {
     out
 }
 
-fn values_of(doc: &Document, o: Option<&Object>) -> Vec<String> {
+fn values_of(doc: &Document, o: Option<&Object>, kind: FieldKind) -> Vec<String> {
     let Some(o) = o else { return Vec::new() };
+    // "Off" is a button's off state; in a text or choice field it is the value.
+    let button = matches!(kind, FieldKind::CheckBox | FieldKind::Radio);
     match &*doc.resolve(o) {
         Object::Array(a) => a.iter().filter_map(|x| text_of(&doc.resolve(x))).collect(),
         Object::Stream(s) => s.decoded().ok().map(|b| PdfString::literal(b).to_text()).into_iter().collect(),
-        other => text_of(other).filter(|s| s != "Off" && !s.is_empty()).into_iter().collect(),
+        other => text_of(other).filter(|s| !(button && s == "Off") && !s.is_empty()).into_iter().collect(),
     }
 }
 
@@ -818,8 +820,8 @@ fn walk(
         name: inh.name.clone(),
         obj: r,
         kind,
-        value: values_of(doc, inh.v.as_ref()),
-        default: values_of(doc, inh.dv.as_ref()),
+        value: values_of(doc, inh.v.as_ref(), kind),
+        default: values_of(doc, inh.dv.as_ref(), kind),
         flags: ff,
         max_len: inh.max_len,
         options,

crates/forms/src/tests.rs

@@ -1850,3 +1850,23 @@ fn invalid_appearance_patches_are_refused_before_anything_is_written() {
     assert!(set_props(&mut doc, "name", &props).is_err());
     assert_eq!(write_incremental(&doc, &SaveOptions::default()).unwrap(), before);
 }
+
+/// "Off" is a button's off state, not a value; a text or choice field that holds "Off" reads
+/// it (#1320), while an unchecked check box still reads as no value.
+#[test]
+fn a_literal_off_value_reads_as_off_outside_buttons() {
+    for (kind, value) in [
+        (NewField::Text { multiline: false }, FieldValue::Text("Off".into())),
+        (NewField::Combo { options: vec!["On".into(), "Off".into()], editable: false }, FieldValue::Choice(vec!["Off".into()])),
+        (NewField::List { options: vec!["On".into(), "Off".into()], multi: false }, FieldValue::Choice(vec!["Off".into()])),
+    ] {
+        let mut doc = one_page();
+        add_field(&mut doc, 0, [50.0, 600.0, 250.0, 620.0], &kind, Some("power")).unwrap();
+        set_value(&mut doc, "power", &value).unwrap();
+        assert_eq!(field(&fields(&reopen(&doc)), "power").value, ["Off"], "{kind:?}");
+    }
+    let mut doc = one_page();
+    add_field(&mut doc, 0, [50.0, 600.0, 70.0, 620.0], &NewField::CheckBox, Some("power")).unwrap();
+    set_value(&mut doc, "power", &FieldValue::Check(false)).unwrap();
+    assert!(field(&fields(&doc), "power").value.is_empty());
+}