Trim Text events after DOCTYPE so spaces does not produce an event.

Otherwise consequent `Text` events (which is possible if their delimited by
Comment or PI events, which is skipped) will be merged but not trimmed.
That will lead to returning a `Text` event when try to call `deserialize_struct`
or `deserialize_map` which will trigger `DeError::ExpectedStart` error.

The incorrect trim behavior was introduced in #581, when DocType event began to be processed

Changelog.md

@@ -18,9 +18,15 @@
 
 ### Bug Fixes
 
+- [#603]: Fix a regression from [#581] that an XML comment or a processing
+  instruction between a <!DOCTYPE> and the root element in the file brokes
+  deserialization of structs by returning `DeError::ExpectedStart`
+
 ### Misc Changes
 
+[#581]: https://github.com/tafia/quick-xml/pull/581
 [#601]: https://github.com/tafia/quick-xml/pull/601
+[#603]: https://github.com/tafia/quick-xml/pull/603
 [#606]: https://github.com/tafia/quick-xml/pull/606
 
 

src/de/mod.rs

@@ -2880,7 +2880,7 @@ impl StartTrimmer {
     #[inline(always)]
     fn trim<'a>(&mut self, event: Event<'a>) -> Option<PayloadEvent<'a>> {
         let (event, trim_next_event) = match event {
-            Event::DocType(e) => (PayloadEvent::DocType(e), false),
+            Event::DocType(e) => (PayloadEvent::DocType(e), true),
             Event::Start(e) => (PayloadEvent::Start(e), true),
             Event::End(e) => (PayloadEvent::End(e), true),
             Event::Eof => (PayloadEvent::Eof, true),