tafia · Mingun · Jun 2, 2023 · Jun 2, 2023 · Jun 2, 2023 · Jun 2, 2023
diff --git a/Changelog.md b/Changelog.md
@@ -14,12 +14,14 @@
 
 - [#601]: Add `serde_helper` module to the crate root with some useful utility
   functions and document using of enum's unit variants as a text content of element.
+- [#606]: Implement indentation for `AsyncWrite` trait implementations.
 
 ### Bug Fixes
 
 ### Misc Changes
 
 [#601]: https://github.com/tafia/quick-xml/pull/601
+[#606]: https://github.com/tafia/quick-xml/pull/606
 
 
 ## 0.28.2 -- 2023-04-12

diff --git a/src/writer.rs b/src/writer.rs
@@ -71,6 +71,14 @@ impl<W> Writer<W> {
         }
     }
 
+    /// Creates a `Writer` with configured indents from a generic writer.
+    pub fn new_with_indent(inner: W, indent_char: u8, indent_size: usize) -> Writer<W> {
+        Writer {
+            writer: inner,
+            indent: Some(Indentation::new(indent_char, indent_size)),
+        }
+    }
+
     /// Consumes this `Writer`, returning the underlying writer.
     pub fn into_inner(self) -> W {
         self.writer
@@ -88,14 +96,6 @@ impl<W> Writer<W> {
 }
 
 impl<W: Write> Writer<W> {
-    /// Creates a `Writer` with configured whitespace indents from a generic writer.
-    pub fn new_with_indent(inner: W, indent_char: u8, indent_size: usize) -> Writer<W> {
-        Writer {
-            writer: inner,
-            indent: Some(Indentation::new(indent_char, indent_size)),
-        }
-    }
-
     /// Write a [Byte-Order-Mark] character to the document.
     ///
     /// # Example

diff --git a/src/writer/async_tokio.rs b/src/writer/async_tokio.rs
@@ -7,13 +7,29 @@ use crate::Writer;
 impl<W: AsyncWrite + Unpin> Writer<W> {
     /// Writes the given event to the underlying writer. Async version of [`Writer::write_event`].
     pub async fn write_event_async<'a, E: AsRef<Event<'a>>>(&mut self, event: E) -> Result<()> {
-        match *event.as_ref() {
-            Event::Start(ref e) => self.write_wrapped_async(b"<", e, b">").await,
-            Event::End(ref e) => self.write_wrapped_async(b"</", e, b">").await,
+        let mut next_should_line_break = true;
+        let result = match *event.as_ref() {
+            Event::Start(ref e) => {
+                let result = self.write_wrapped_async(b"<", e, b">").await;
+                if let Some(i) = self.indent.as_mut() {
+                    i.grow();
+                }
+                result
+            }
+            Event::End(ref e) => {
+                if let Some(i) = self.indent.as_mut() {
+                    i.shrink();
+                }
+                self.write_wrapped_async(b"</", e, b">").await
+            }
             Event::Empty(ref e) => self.write_wrapped_async(b"<", e, b"/>").await,
-            Event::Text(ref e) => self.write_async(e).await,
+            Event::Text(ref e) => {
+                next_should_line_break = false;
+                self.write_async(e).await
+            }
             Event::Comment(ref e) => self.write_wrapped_async(b"<!--", e, b"-->").await,
             Event::CData(ref e) => {
+                next_should_line_break = false;
                 self.write_async(b"<![CDATA[").await?;
                 self.write_async(e).await?;
                 self.write_async(b"]]>").await
@@ -22,7 +38,23 @@ impl<W: AsyncWrite + Unpin> Writer<W> {
             Event::PI(ref e) => self.write_wrapped_async(b"<?", e, b"?>").await,
             Event::DocType(ref e) => self.write_wrapped_async(b"<!DOCTYPE ", e, b">").await,
             Event::Eof => Ok(()),
+        };
+        if let Some(i) = self.indent.as_mut() {
+            i.should_line_break = next_should_line_break;
+        }
+        result
+    }
+
+    /// Manually write a newline and indentation at the proper level. Async version of
+    /// [`Writer::write_indent`].
+    ///
+    /// This method will do nothing if `Writer` was not constructed with [`Writer::new_with_indent`].
+    pub async fn write_indent_async(&mut self) -> Result<()> {
+        if let Some(ref i) = self.indent {
+            self.writer.write_all(b"\n").await?;
+            self.writer.write_all(i.current()).await?;
         }
+        Ok(())
     }
 
     #[inline]
@@ -37,6 +69,12 @@ impl<W: AsyncWrite + Unpin> Writer<W> {
         value: &[u8],
         after: &[u8],
     ) -> Result<()> {
+        if let Some(ref i) = self.indent {
+            if i.should_line_break {
+                self.writer.write_all(b"\n").await?;
+                self.writer.write_all(i.current()).await?;
+            }
+        }
         self.write_async(before).await?;
         self.write_async(value).await?;
         self.write_async(after).await?;
@@ -117,3 +155,188 @@ mod tests {
         );
     }
 }
+
+#[cfg(test)]
+mod indentation_async {
+    use super::*;
+    use crate::events::*;
+    use pretty_assertions::assert_eq;
+
+    #[tokio::test]
+    async fn self_closed() {
+        let mut buffer = Vec::new();
+        let mut writer = Writer::new_with_indent(&mut buffer, b' ', 4);
+
+        let tag = BytesStart::new("self-closed")
+            .with_attributes(vec![("attr1", "value1"), ("attr2", "value2")].into_iter());
+        writer
+            .write_event_async(Event::Empty(tag))
+            .await
+            .expect("write tag failed");
+
+        assert_eq!(
+            std::str::from_utf8(&buffer).unwrap(),
+            r#"<self-closed attr1="value1" attr2="value2"/>"#
+        );
+    }
+
+    #[tokio::test]
+    async fn empty_paired() {
+        let mut buffer = Vec::new();
+        let mut writer = Writer::new_with_indent(&mut buffer, b' ', 4);
+
+        let start = BytesStart::new("paired")
+            .with_attributes(vec![("attr1", "value1"), ("attr2", "value2")].into_iter());
+        let end = start.to_end();
+        writer
+            .write_event_async(Event::Start(start.clone()))
+            .await
+            .expect("write start tag failed");
+        writer
+            .write_event_async(Event::End(end))
+            .await
+            .expect("write end tag failed");
+
+        assert_eq!(
+            std::str::from_utf8(&buffer).unwrap(),
+            r#"<paired attr1="value1" attr2="value2">
+</paired>"#
+        );
+    }
+
+    #[tokio::test]
+    async fn paired_with_inner() {
+        let mut buffer = Vec::new();
+        let mut writer = Writer::new_with_indent(&mut buffer, b' ', 4);
+
+        let start = BytesStart::new("paired")
+            .with_attributes(vec![("attr1", "value1"), ("attr2", "value2")].into_iter());
+        let end = start.to_end();
+        let inner = BytesStart::new("inner");
+
+        writer
+            .write_event_async(Event::Start(start.clone()))
+            .await
+            .expect("write start tag failed");
+        writer
+            .write_event_async(Event::Empty(inner))
+            .await
+            .expect("write inner tag failed");
+        writer
+            .write_event_async(Event::End(end))
+            .await
+            .expect("write end tag failed");
+
+        assert_eq!(
+            std::str::from_utf8(&buffer).unwrap(),
+            r#"<paired attr1="value1" attr2="value2">
+    <inner/>
+</paired>"#
+        );
+    }
+
+    #[tokio::test]
+    async fn paired_with_text() {
+        let mut buffer = Vec::new();
+        let mut writer = Writer::new_with_indent(&mut buffer, b' ', 4);
+
+        let start = BytesStart::new("paired")
+            .with_attributes(vec![("attr1", "value1"), ("attr2", "value2")].into_iter());
+        let end = start.to_end();
+        let text = BytesText::new("text");
+
+        writer
+            .write_event_async(Event::Start(start.clone()))
+            .await
+            .expect("write start tag failed");
+        writer
+            .write_event_async(Event::Text(text))
+            .await
+            .expect("write text failed");
+        writer
+            .write_event_async(Event::End(end))
+            .await
+            .expect("write end tag failed");
+
+        assert_eq!(
+            std::str::from_utf8(&buffer).unwrap(),
+            r#"<paired attr1="value1" attr2="value2">text</paired>"#
+        );
+    }
+
+    #[tokio::test]
+    async fn mixed_content() {
+        let mut buffer = Vec::new();
+        let mut writer = Writer::new_with_indent(&mut buffer, b' ', 4);
+
+        let start = BytesStart::new("paired")
+            .with_attributes(vec![("attr1", "value1"), ("attr2", "value2")].into_iter());
+        let end = start.to_end();
+        let text = BytesText::new("text");
+        let inner = BytesStart::new("inner");
+
+        writer
+            .write_event_async(Event::Start(start.clone()))
+            .await
+            .expect("write start tag failed");
+        writer
+            .write_event_async(Event::Text(text))
+            .await
+            .expect("write text failed");
+        writer
+            .write_event_async(Event::Empty(inner))
+            .await
+            .expect("write inner tag failed");
+        writer
+            .write_event_async(Event::End(end))
+            .await
+            .expect("write end tag failed");
+
+        assert_eq!(
+            std::str::from_utf8(&buffer).unwrap(),
+            r#"<paired attr1="value1" attr2="value2">text<inner/>
+</paired>"#
+        );
+    }
+
+    #[tokio::test]
+    async fn nested() {
+        let mut buffer = Vec::new();
+        let mut writer = Writer::new_with_indent(&mut buffer, b' ', 4);
+
+        let start = BytesStart::new("paired")
+            .with_attributes(vec![("attr1", "value1"), ("attr2", "value2")].into_iter());
+        let end = start.to_end();
+        let inner = BytesStart::new("inner");
+
+        writer
+            .write_event_async(Event::Start(start.clone()))
+            .await
+            .expect("write start 1 tag failed");
+        writer
+            .write_event_async(Event::Start(start.clone()))
+            .await
+            .expect("write start 2 tag failed");
+        writer
+            .write_event_async(Event::Empty(inner))
+            .await
+            .expect("write inner tag failed");
+        writer
+            .write_event_async(Event::End(end.clone()))
+            .await
+            .expect("write end tag 2 failed");
+        writer
+            .write_event_async(Event::End(end))
+            .await
+            .expect("write end tag 1 failed");
+
+        assert_eq!(
+            std::str::from_utf8(&buffer).unwrap(),
+            r#"<paired attr1="value1" attr2="value2">
+    <paired attr1="value1" attr2="value2">
+        <inner/>
+    </paired>
+</paired>"#
+        );
+    }
+}