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Merged
Mingun merged 2 commits into from
Dec 21, 2025
+226 −41
Merged

Optionally add a space before the trailing slash in unexpanded empty elements #922

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7d6e7cd
Add `writer::Config` struct for configuring writer behavior. Allow sp…
Mingun Dec 20, 2025
b90476e
Fix #846 by optionally adding a space before the trailing slash in un…
zrneely Dec 19, 2025
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10 changes: 10 additions & 0 deletions Changelog.md
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Original file line number Diff line number Diff line change
Expand Up @@ -14,8 +14,17 @@

## Unreleased

Added a way to configure `Writer`. Now all configuration is contained in the `writer::Config`
struct and can be applied at once. When `serde-types` feature is enabled, configuration is serializable.

### New Features

- [#846]: Add methods `config()` and `config_mut()` to inspect and change the writer configuration.
- [#846]: Add ability to write space before `/>` in self-closed tags for maximum compatibility with
XHTML.
- [#846]: Add method `empty_element_handling()` as a more powerful alternative to `expand_empty_elements()`
in `Serializer`.

### Bug Fixes

### Misc Changes
Expand All @@ -25,6 +34,7 @@
of `NsReader`. Use `.resolver().bindings()` and `.resolver().resolve()` methods instead.
- [#913]: `Attributes::has_nil` now accepts `NamespaceResolver` instead of `Reader<R>`.

[#846]: https://github.com/tafia/quick-xml/issues/846
[#908]: https://github.com/tafia/quick-xml/pull/908
[#913]: https://github.com/tafia/quick-xml/pull/913

Expand Down
49 changes: 30 additions & 19 deletions src/se/content.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,9 @@
use crate::de::TEXT_KEY;
use crate::se::element::{ElementSerializer, Struct, Tuple};
use crate::se::simple_type::{QuoteTarget, SimpleTypeSerializer};
use crate::se::{Indent, QuoteLevel, SeError, TextFormat, WriteResult, XmlName};
use crate::se::{
EmptyElementHandling, Indent, QuoteLevel, SeError, TextFormat, WriteResult, XmlName,
};
use serde::ser::{
Impossible, Serialize, SerializeSeq, SerializeTuple, SerializeTupleStruct, Serializer,
};
Expand Down Expand Up @@ -80,9 +82,8 @@ pub struct ContentSerializer<'w, 'i, W: Write> {
/// as a text that makes it impossible to distinguish between them during
/// deserialization. Instead of ambiguous serialization the error is returned.
pub allow_primitive: bool,
// If `true`, then empty elements will be serialized as `<element></element>`
// instead of `<element/>`.
pub expand_empty_elements: bool,
/// Specifies how empty elements are written.
pub empty_element_handling: EmptyElementHandling,
}

impl<'w, 'i, W: Write> ContentSerializer<'w, 'i, W> {
Expand Down Expand Up @@ -124,25 +125,35 @@ impl<'w, 'i, W: Write> ContentSerializer<'w, 'i, W> {
write_indent: self.write_indent,
text_format: self.text_format,
allow_primitive,
expand_empty_elements: self.expand_empty_elements,
empty_element_handling: self.empty_element_handling,
}
}

/// Writes `name` as self-closed tag
#[inline]
pub(super) fn write_empty(mut self, name: XmlName) -> Result<WriteResult, SeError> {
self.write_indent()?;
if self.expand_empty_elements {
self.writer.write_char('<')?;
self.writer.write_str(name.0)?;
self.writer.write_str("></")?;
self.writer.write_str(name.0)?;
self.writer.write_char('>')?;
} else {
self.writer.write_str("<")?;
self.writer.write_str(name.0)?;
self.writer.write_str("/>")?;

match self.empty_element_handling {
EmptyElementHandling::SelfClosed => {
self.writer.write_char('<')?;
self.writer.write_str(name.0)?;
self.writer.write_str("/>")?;
}
EmptyElementHandling::SelfClosedWithSpace => {
self.writer.write_char('<')?;
self.writer.write_str(name.0)?;
self.writer.write_str(" />")?;
}
EmptyElementHandling::Expanded => {
self.writer.write_char('<')?;
self.writer.write_str(name.0)?;
self.writer.write_str("></")?;
self.writer.write_str(name.0)?;
self.writer.write_char('>')?;
}
}

Ok(WriteResult::Element)
}

Expand Down Expand Up @@ -604,7 +615,7 @@ pub(super) mod tests {
write_indent: false,
text_format: TextFormat::Text,
allow_primitive: true,
expand_empty_elements: false,
empty_element_handling: EmptyElementHandling::SelfClosed,
};

let result = $data.serialize(ser).unwrap();
Expand All @@ -628,7 +639,7 @@ pub(super) mod tests {
write_indent: false,
text_format: TextFormat::Text,
allow_primitive: true,
expand_empty_elements: false,
empty_element_handling: EmptyElementHandling::SelfClosed,
};

match $data.serialize(ser).unwrap_err() {
Expand Down Expand Up @@ -1070,7 +1081,7 @@ pub(super) mod tests {
write_indent: false,
text_format: TextFormat::Text,
allow_primitive: true,
expand_empty_elements: false,
empty_element_handling: EmptyElementHandling::SelfClosed,
};

let result = $data.serialize(ser).unwrap();
Expand All @@ -1094,7 +1105,7 @@ pub(super) mod tests {
write_indent: false,
text_format: TextFormat::Text,
allow_primitive: true,
expand_empty_elements: false,
empty_element_handling: EmptyElementHandling::SelfClosed,
};

match $data.serialize(ser).unwrap_err() {
Expand Down
32 changes: 19 additions & 13 deletions src/se/element.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ use crate::se::content::ContentSerializer;
use crate::se::key::QNameSerializer;
use crate::se::simple_type::{QuoteTarget, SimpleSeq, SimpleTypeSerializer};
use crate::se::text::TextSerializer;
use crate::se::{SeError, WriteResult, XmlName};
use crate::se::{EmptyElementHandling, SeError, WriteResult, XmlName};
use serde::ser::{
Impossible, Serialize, SerializeMap, SerializeSeq, SerializeStruct, SerializeStructVariant,
SerializeTuple, SerializeTupleStruct, SerializeTupleVariant, Serializer,
Expand Down Expand Up @@ -442,7 +442,7 @@ impl<'w, 'k, W: Write> Struct<'w, 'k, W> {
write_indent: self.write_indent,
text_format: self.ser.ser.text_format,
allow_primitive: true,
expand_empty_elements: self.ser.ser.expand_empty_elements,
empty_element_handling: self.ser.ser.empty_element_handling,
};

if key == TEXT_KEY {
Expand Down Expand Up @@ -479,12 +479,18 @@ impl<'w, 'k, W: Write> SerializeStruct for Struct<'w, 'k, W> {
self.ser.ser.indent.decrease();

if self.children.is_empty() {
if self.ser.ser.expand_empty_elements {
self.ser.ser.writer.write_str("></")?;
self.ser.ser.writer.write_str(self.ser.key.0)?;
self.ser.ser.writer.write_char('>')?;
} else {
self.ser.ser.writer.write_str("/>")?;
match self.ser.ser.empty_element_handling {
EmptyElementHandling::SelfClosed => {
self.ser.ser.writer.write_str("/>")?;
}
EmptyElementHandling::SelfClosedWithSpace => {
self.ser.ser.writer.write_str(" />")?;
}
EmptyElementHandling::Expanded => {
self.ser.ser.writer.write_str("></")?;
self.ser.ser.writer.write_str(self.ser.key.0)?;
self.ser.ser.writer.write_char('>')?;
}
}
} else {
self.ser.ser.writer.write_char('>')?;
Expand Down Expand Up @@ -635,7 +641,7 @@ mod tests {
write_indent: false,
text_format: TextFormat::Text,
allow_primitive: true,
expand_empty_elements: false,
empty_element_handling: EmptyElementHandling::SelfClosed,
},
key: XmlName("root"),
};
Expand All @@ -662,7 +668,7 @@ mod tests {
write_indent: false,
text_format: TextFormat::Text,
allow_primitive: true,
expand_empty_elements: false,
empty_element_handling: EmptyElementHandling::SelfClosed,
},
key: XmlName("root"),
};
Expand Down Expand Up @@ -1348,7 +1354,7 @@ mod tests {
write_indent: false,
text_format: TextFormat::Text,
allow_primitive: true,
expand_empty_elements: false,
empty_element_handling: EmptyElementHandling::SelfClosed,
},
key: XmlName("root"),
};
Expand All @@ -1375,7 +1381,7 @@ mod tests {
write_indent: false,
text_format: TextFormat::Text,
allow_primitive: true,
expand_empty_elements: false,
empty_element_handling: EmptyElementHandling::SelfClosed,
},
key: XmlName("root"),
};
Expand Down Expand Up @@ -2083,7 +2089,7 @@ mod tests {
write_indent: false,
text_format: TextFormat::Text,
allow_primitive: true,
expand_empty_elements: true,
empty_element_handling: EmptyElementHandling::Expanded,
},
key: XmlName("root"),
};
Expand Down
96 changes: 89 additions & 7 deletions src/se/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -373,6 +373,26 @@ pub enum QuoteLevel {
Minimal,
}

/// Specifies how empty elements are serialized.
/// The default is self-closed with no space before the slash.
#[derive(Debug, Default, Copy, Clone, PartialEq, Eq)]
pub enum EmptyElementHandling {
/// Empty elements will be written as `<element/>`. This is the default behavior.
#[default]
SelfClosed,

/// The same, as [`SelfClosed`], but an extra space will be written before
/// the slash, so empty elements will be written as `<element />`.
/// This is recommended by the [W3C guidelines] for XHTML.
///
/// [`SelfClosed`]: Self::SelfClosed
/// [W3C guidelines]: https://www.w3.org/TR/xhtml1/#guidelines
SelfClosedWithSpace,

/// Empty elements will be expanded, as in: `<element></element>`.
Expanded,
}

/// Classification of the type written by the serializer.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum WriteResult {
Expand Down Expand Up @@ -568,7 +588,7 @@ impl<'w, 'r, W: Write> Serializer<'w, 'r, W> {
write_indent: false,
text_format: TextFormat::Text,
allow_primitive: true,
expand_empty_elements: false,
empty_element_handling: EmptyElementHandling::SelfClosed,
},
root_tag: None,
}
Expand Down Expand Up @@ -635,21 +655,80 @@ impl<'w, 'r, W: Write> Serializer<'w, 'r, W> {
write_indent: false,
text_format: TextFormat::Text,
allow_primitive: true,
expand_empty_elements: false,
empty_element_handling: EmptyElementHandling::SelfClosed,
},
root_tag: root_tag.map(XmlName::try_from).transpose()?,
})
}

/// Enable or disable expansion of empty elements. Defaults to `false`.
/// Enable or disable expansion of empty elements. Defaults to [`EmptyElementHandling::SelfClosed`].
///
/// # Examples
///
/// ```
/// # use pretty_assertions::assert_eq;
/// # use serde::Serialize;
/// # use quick_xml::se::Serializer;
/// # use quick_xml::se::{Serializer, EmptyElementHandling};
/// #
/// #[derive(Debug, PartialEq, Serialize)]
/// struct Struct {
/// question: Option<String>,
/// }
///
/// let data = Struct {
/// question: None,
/// };
///
/// {
/// let mut buffer = String::new();
/// let mut ser = Serializer::new(&mut buffer);
/// ser.empty_element_handling(EmptyElementHandling::SelfClosed);
/// data.serialize(ser).unwrap();
/// assert_eq!(
/// buffer,
/// "<Struct><question/></Struct>"
/// );
/// }
///
/// {
/// let mut buffer = String::new();
/// let mut ser = Serializer::new(&mut buffer);
/// ser.empty_element_handling(EmptyElementHandling::SelfClosedWithSpace);
/// data.serialize(ser).unwrap();
/// assert_eq!(
/// buffer,
/// "<Struct><question /></Struct>"
/// );
/// }
///
/// {
/// let mut buffer = String::new();
/// let mut ser = Serializer::new(&mut buffer);
/// ser.empty_element_handling(EmptyElementHandling::Expanded);
/// data.serialize(ser).unwrap();
/// assert_eq!(
/// buffer,
/// "<Struct><question></question></Struct>"
/// );
/// }
/// ```
pub fn empty_element_handling(&mut self, handling: EmptyElementHandling) -> &mut Self {
self.ser.empty_element_handling = handling;
self
}

/// Enable or disable expansion of empty elements (without adding space before `/>`).
///
/// This is the historycally first way to configure empty element handling. You can use
/// [`empty_element_handling`](Self::empty_element_handling) for more control.
///
/// # Examples
///
/// ```
/// # use pretty_assertions::assert_eq;
/// # use serde::Serialize;
/// # use quick_xml::se::Serializer;
/// #
/// #[derive(Debug, PartialEq, Serialize)]
/// struct Struct {
/// question: Option<String>,
Expand All @@ -660,7 +739,7 @@ impl<'w, 'r, W: Write> Serializer<'w, 'r, W> {
/// ser.expand_empty_elements(true);
///
/// let data = Struct {
/// question: None,
/// question: None,
/// };
///
/// data.serialize(ser).unwrap();
Expand All @@ -670,8 +749,11 @@ impl<'w, 'r, W: Write> Serializer<'w, 'r, W> {
/// );
/// ```
pub fn expand_empty_elements(&mut self, expand: bool) -> &mut Self {
self.ser.expand_empty_elements = expand;
self
self.empty_element_handling(if expand {
EmptyElementHandling::Expanded
} else {
EmptyElementHandling::SelfClosed
})
}

/// Set the text format used for serializing text content.
Expand Down
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