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Trim next element after DocType #603

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merged 2 commits into from
Jun 10, 2023
Merged

Trim next element after DocType #603

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c8332d9
Add tests for comments and processing instructions in XML prolog
May 24, 2023
d49f2d5
Trim `Text` events after DOCTYPE so spaces does not produce an event.
Jun 9, 2023
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6 changes: 6 additions & 0 deletions Changelog.md
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Expand Up @@ -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


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2 changes: 1 addition & 1 deletion src/de/mod.rs
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Expand Up @@ -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),
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Could you add a comment describing, why we need trim here because this is not obvious (otherwise it would be done initially)

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Immediately following a Doctype event, the Serde parser expects to read an initial structure from the XML file - it expects a 'Start' tag event. Any comments following the doctype in the stream is parsed to Text/CData events, which leads the parse to fail with an 'ExpectedStart' panic. By skipping (trimming) any Text/CData events the next event the serde deserializer sees will be a Start event, which is always required to start building up a new Struct from the xml.

The Doctype should trim events here just like the Start/End events. Only the CData/Text events should not trim (otherwise any CData/Text following them will be ignored)

Event::Start(e) => (PayloadEvent::Start(e), true),
Event::End(e) => (PayloadEvent::End(e), true),
Event::Eof => (PayloadEvent::Eof, true),
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74 changes: 74 additions & 0 deletions tests/serde-de.rs
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Expand Up @@ -6496,3 +6496,77 @@ mod resolve {
);
}
}

/// Tests for https://github.com/tafia/quick-xml/pull/603.
///
/// According to <https://www.w3.org/TR/xml11/#NT-prolog> comments,
/// processing instructions and spaces are possible after XML declaration or DTD.
/// Their existence should not break deserializing
///
/// ```text
/// [22] prolog ::= XMLDecl Misc* (doctypedecl Misc*)?
/// [27] Misc ::= Comment | PI | S
/// ```
mod xml_prolog {
use super::*;
use pretty_assertions::assert_eq;
use std::collections::HashMap;

#[test]
fn spaces() {
assert_eq!(
from_str::<HashMap<(), ()>>(
r#"
<?xml version="1.1"?>

<!DOCTYPE dict>

<doc>
</doc>
"#
)
.unwrap(),
HashMap::new()
);
}

#[test]
fn comments() {
assert_eq!(
from_str::<HashMap<(), ()>>(
r#"
<?xml version="1.1"?>
<!-- comment between xml declaration and doctype -->
<!-- another comment -->
<!DOCTYPE dict>
<!-- comment between doctype and root element -->
<!-- another comment -->
<doc>
</doc>
"#,
)
.unwrap(),
HashMap::new()
);
}

#[test]
fn pi() {
assert_eq!(
from_str::<HashMap<(), ()>>(
r#"
<?xml version="1.1"?>
<?pi?>
<?another pi?>
<!DOCTYPE dict>
<?pi?>
<?another pi?>
<doc>
</doc>
"#,
)
.unwrap(),
HashMap::new()
);
}
}