tamer: xir::reader: Correct empty element whitespace handling

This both adds clarifying tests and corrects the case of `<foo/>`, where the
offset was erroneously off by one---it saw that there were no attributes and
added a byte thinking it'd include `>`, as in `<foo>`.

DEV-7145

tamer/src/xir/reader.rs

@@ -137,6 +137,7 @@ impl<'s, B: BufRead, S: Escaper> XmlXirReader<'s, B, S> {
                         ele,
                         prev_pos,
                         ctx,
+                        true,
                     )
                     .and_then(|open| {
                         let new_pos = self.reader.buffer_position();
@@ -160,6 +161,7 @@ impl<'s, B: BufRead, S: Escaper> XmlXirReader<'s, B, S> {
                     ele,
                     prev_pos,
                     ctx,
+                    false,
                 )),
 
                 QuickXmlEvent::End(ele) => Some({
@@ -297,6 +299,7 @@ impl<'s, B: BufRead, S: Escaper> XmlXirReader<'s, B, S> {
         ele: BytesStart,
         pos: usize,
         ctx: Context,
+        empty_tag: bool,
     ) -> Result<Token> {
         // Starts after the opening tag `<`, so adjust.
         let addr = ele.as_ptr() as usize - 1;
@@ -340,13 +343,13 @@ impl<'s, B: BufRead, S: Escaper> XmlXirReader<'s, B, S> {
             .map_err(Error::from_with_span(ctx.span_or_zz(pos + 1, len)))
             .and_then(|qname| {
                 let has_attrs = ele.attributes_raw().len() > 0;
-                let noattr_add: usize = (!has_attrs).into();
+                let noattr_add: usize = (!has_attrs && !empty_tag).into();
 
-                // <tag ... />
-                // [--]  name + '<'
+                // <tag ... />               <tag/>
+                // [--]  name + '<'          [--] `noattr_add` must be 0
                 //
-                // <tag>..</tag>
-                // [---] name + '<' + '>'
+                // <tag>...</tag>            <tag ...>...</tag>
+                // [---] name + '<' + '>'    [--] name + '<'
                 let span = ctx.span_or_zz(pos, len + 1 + noattr_add);
 
                 if has_attrs {

tamer/src/xir/reader/test.rs

@@ -94,14 +94,36 @@ macro_rules! new_sut {
 }
 
 #[test]
-fn empty_node_without_prefix_or_attributes() {
-    new_sut!(sut = "<empty-node />");
-    //              [---------] []
+fn empty_node_without_prefix_or_attributes_or_whitespace() {
+    new_sut!(sut = "<empty-node/>");
+    //              [---------][]
     //              0        10
-    //                   A      B
+    //                   A     B
 
     let a = DC.span(0, 11);
-    let b = DC.span(12, 2);
+    let b = DC.span(11, 2);
+
+    assert_eq!(
+        Ok(vec![
+            O(Token::Open("empty-node".unwrap_into(), a)),
+            O(Token::Close(None, b)),
+        ]),
+        sut.collect(),
+    );
+}
+
+#[test]
+fn empty_node_without_prefix_or_attributes() {
+    new_sut!(sut = "<empty-node   />");
+    //              [---------]   []
+    //              0        10  14
+    //                   A        B
+    //
+    //            (extra WS intentional to test
+    //             how it accommodates with spans)
+
+    let a = DC.span(0, 11);
+    let b = DC.span(14, 2);
 
     assert_eq!(
         Ok(vec![
@@ -808,3 +830,21 @@ fn empty_element_qname_with_space_with_attr() {
         sut.collect::<SutResultCollect>()
     );
 }
+
+// Same as above test except that we have no attrs.
+// We just want to be sure that we can't have a QName that starts with
+//   whitespace.
+#[test]
+fn space_before_element_name() {
+    new_sut!(sut = r#"< foo />"#);
+    //                 |
+    //                 1
+    //   quick-xml interprets the space as a "" QName
+
+    let span = DC.span(1, 0);
+
+    assert_eq!(
+        Err(PE(Error::InvalidQName("".intern(), span))),
+        sut.collect::<SutResultCollect>()
+    );
+}