Fix incorrect decreasing of nesting level in NamespaceResolver

src/reader/ns_reader.rs

@@ -10,7 +10,7 @@ use std::ops::Deref;
 use std::path::Path;
 
 use crate::errors::Result;
-use crate::events::{BytesText, Event};
+use crate::events::{BytesStart, BytesText, Event};
 use crate::name::{NamespaceResolver, QName, ResolveResult};
 use crate::reader::{Config, Reader, Span, XmlSource};
 
@@ -91,6 +91,10 @@ impl<R> NsReader<R> {
                 Ok(Event::Empty(e))
             }
             Ok(Event::End(e)) => {
+                // push a fake element to the `ns_resolver` as the pending pop will remove it again
+                // if we don't push this element we don't increase the level, but the subsequent pending pop will
+                // decrease it anyway.
+                self.ns_resolver.push(&BytesStart::new(""))?;
                 // notify next `read_event_impl()` invocation that it needs to pop this
                 // namespace scope
                 self.pending_pop = true;

tests/serde-de-xsi.rs

@@ -702,3 +702,48 @@ mod as_field {
         }
     }
 }
+
+/// Regression test for https://github.com/tafia/quick-xml/issues/953.
+mod issue953 {
+    use super::*;
+
+    #[derive(Debug, Deserialize)]
+    struct BoreholeType {
+        #[serde(rename = "boreholeSegment")]
+        borehole_segment: Vec<()>,
+
+        #[serde(rename = "drillingProcess")]
+        drilling_process: Option<DrillingProcess>,
+    }
+
+    #[derive(Debug, Deserialize)]
+    struct DrillingProcess {
+        #[serde(rename = "DrillingProcess")]
+        drilling_process: (),
+    }
+
+    // success before 210d3e1d460a4c63e13d455b0b15623b77fa669c
+    // failed since 210d3e1d460a4c63e13d455b0b15623b77fa669c
+    #[test]
+    fn open_close() {
+        let input = r#"
+        <Borehole xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+          <boreholeSegment> </boreholeSegment>
+          <drillingProcess xsi:nil="true"/>
+        </Borehole>
+        "#;
+        let _: BoreholeType = from_str(&input).unwrap();
+    }
+
+    // failed always
+    #[test]
+    fn self_closed() {
+        let input = r#"
+        <Borehole xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+          <boreholeSegment/>
+          <drillingProcess xsi:nil="true"/>
+        </Borehole>
+        "#;
+        let _: BoreholeType = from_str(&input).unwrap();
+    }
+}