Provide a 'only_child' blanket implementation

src/minidom_utils/try_only_child.rs

@@ -35,6 +35,12 @@ pub trait TryOnlyChild {
     fn try_only_child<'a>(&'a self, child_name: &str) -> Result<&'a Self> {
         self.try_only_child_with_filter(child_name, |_| true)
     }
+
+    /// Get a unique child from its name and return an [Option](std::Option)
+    /// Returns None if the child can't be found or if the child is not unique
+    fn only_child<'a>(&'a self, child_name: &str) -> Option<&'a Self> {
+        self.try_only_child(child_name).ok()
+    }
 }
 
 impl TryOnlyChild for Element {

src/netex_idf/lines.rs

@@ -56,8 +56,8 @@ fn load_netex_lines(
             for line in lines_node.children().filter(|e| e.name() == "Line") {
                 let id = line.try_attribute("id")?;
                 let name = line.try_only_child("Name")?.text().parse()?;
-                let code = line.try_only_child("ShortName").map(Element::text).ok();
-                let private_code = line.try_only_child("PrivateCode").map(Element::text).ok();
+                let code = line.only_child("ShortName").map(Element::text);
+                let private_code = line.only_child("PrivateCode").map(Element::text);
                 let network_id = if let Some(network_id) = map_line_network.get(&id) {
                     network_id.to_string()
                 } else {

src/transxchange/read.rs

@@ -166,11 +166,10 @@ fn load_network(transxchange: &Element) -> Result<Network> {
         .trim()
         .to_string();
     let timezone = Some(String::from(EUROPE_LONDON_TIMEZONE));
-    let url = operator.try_only_child("WebSite").map(Element::text).ok();
+    let url = operator.only_child("WebSite").map(Element::text);
     let phone = operator
-        .try_only_child("ContactTelephoneNumber")
-        .map(Element::text)
-        .ok();
+        .only_child("ContactTelephoneNumber")
+        .map(Element::text);
     let network = Network {
         id,
         name,
@@ -437,14 +436,13 @@ fn get_stop_point_activity<'a>(
     vehicle_journey_timing_links
         .iter()
         .find(|vjtl| {
-            vjtl.try_only_child("JourneyPatternTimingLinkRef")
+            vjtl.only_child("JourneyPatternTimingLinkRef")
                 .map(Element::text)
-                .ok()
                 == journey_pattern_timing_link
                     .attr("id")
                     .map(|s| s.to_string())
         })
-        .and_then(|vjtl| vjtl.try_only_child(direction).ok())
+        .and_then(|vjtl| vjtl.only_child(direction))
         .unwrap_or(stop_point)
 }
 
@@ -651,10 +649,9 @@ fn load_routes_vehicle_journeys_calendars(
         )?;
         let route_id = route.id.clone();
         let headsign = journey_pattern
-            .try_only_child("DestinationDisplay")
+            .only_child("DestinationDisplay")
             .map(Element::text)
-            .map(|head_sign| head_sign.trim().to_string())
-            .ok();
+            .map(|head_sign| head_sign.trim().to_string());
 
         // Insert only at the last moment and if no duplicate calendar exist
         if dup_calendar.is_none() {