Support for disabling automatic escaping in to xml (#11536)

# Description
This PR addresses #11525 by adding `--partial-escape` which makes `to
xml` only escape `<>&` in text and `<>&"` in comments. This PR also
fixes issue where comment and PI content was escaped even though [it
should not be](https://stackoverflow.com/a/46637835)

# User-Facing Changes
Correct comments and PIs
 `to xml --partial-escape` flag to emit less escaped characters

# Tests + Formatting
Added tests for specified issues

crates/nu-command/src/formats/to/xml.rs

@@ -7,9 +7,10 @@ use nu_protocol::{
     Category, Example, IntoPipelineData, PipelineData, Record, ShellError, Signature, Span,
     Spanned, SyntaxShape, Type, Value,
 };
+use quick_xml::escape;
 use quick_xml::events::{BytesEnd, BytesStart, BytesText, Event};
+use std::borrow::Cow;
 use std::io::Cursor;
-use std::io::Write;
 
 #[derive(Clone)]
 pub struct ToXml;
@@ -28,6 +29,11 @@ impl Command for ToXml {
                 "Formats the XML text with the provided indentation setting",
                 Some('i'),
             )
+            .switch(
+                "partial-escape",
+                "Only escape mandatory characters in text and attributes",
+                Some('p'),
+            )
             .category(Category::Formats)
     }
 
@@ -65,6 +71,13 @@ Additionally any field which is: empty record, empty list or null, can be omitte
                     "<note>\n   <remember>Event</remember>\n</note>",
                 )),
             },
+            Example {
+                description: "Produce less escaping sequences in resulting xml",
+                example: r#"{tag: note attributes: {a: "'qwe'\\"} content: ["\"'"]} | to xml --partial-escape"#,
+                result: Some(Value::test_string(
+                    r#"<note a="'qwe'\">"'</note>"#
+                ))
+            }
         ]
     }
 
@@ -81,37 +94,107 @@ Additionally any field which is: empty record, empty list or null, can be omitte
     ) -> Result<PipelineData, ShellError> {
         let head = call.head;
         let indent: Option<Spanned<i64>> = call.get_flag(engine_state, stack, "indent")?;
+        let partial_escape = call.has_flag(engine_state, stack, "partial-escape")?;
+
+        let job = Job::new(indent, partial_escape);
         let input = input.try_expand_range()?;
-        to_xml(input, head, indent)
+        job.run(input, head)
     }
 }
 
-pub fn add_attributes<'a>(element: &mut BytesStart<'a>, attributes: &'a IndexMap<String, String>) {
-    for (k, v) in attributes {
-        element.push_attribute((k.as_str(), v.as_str()));
-    }
+struct Job {
+    writer: quick_xml::Writer<Cursor<Vec<u8>>>,
+    partial_escape: bool,
 }
 
-fn to_xml_entry<W: Write>(
-    entry: Value,
-    top_level: bool,
-    writer: &mut quick_xml::Writer<W>,
-) -> Result<(), ShellError> {
-    let entry_span = entry.span();
-    let span = entry.span();
+impl Job {
+    fn new(indent: Option<Spanned<i64>>, partial_escape: bool) -> Self {
+        let writer = indent.as_ref().map_or_else(
+            || quick_xml::Writer::new(Cursor::new(Vec::new())),
+            |p| quick_xml::Writer::new_with_indent(Cursor::new(Vec::new()), b' ', p.item as usize),
+        );
 
-    // Allow using strings directly as content.
-    // So user can write
-    // {tag: a content: ['qwe']}
-    // instead of longer
-    // {tag: a content: [{content: 'qwe'}]}
-    if let (Value::String { val, .. }, false) = (&entry, top_level) {
-        return to_xml_text(val.as_str(), span, writer);
+        Self {
+            writer,
+            partial_escape,
+        }
     }
 
-    if let Value::Record { val: record, .. } = &entry {
-        if let Some(bad_column) = find_invalid_column(record) {
-            return Err(ShellError::CantConvert {
+    fn run(mut self, input: PipelineData, head: Span) -> Result<PipelineData, ShellError> {
+        let value = input.into_value(head);
+
+        self.write_xml_entry(value, true).and_then(|_| {
+            let b = self.writer.into_inner().into_inner();
+            let s = if let Ok(s) = String::from_utf8(b) {
+                s
+            } else {
+                return Err(ShellError::NonUtf8 { span: head });
+            };
+            Ok(Value::string(s, head).into_pipeline_data())
+        })
+    }
+
+    fn add_attributes<'a>(
+        &self,
+        element: &mut BytesStart<'a>,
+        attributes: &'a IndexMap<String, String>,
+    ) {
+        for (k, v) in attributes {
+            if self.partial_escape {
+                element.push_attribute((k.as_bytes(), Self::partial_escape_attribute(v).as_ref()))
+            } else {
+                element.push_attribute((k.as_bytes(), escape::escape(v).as_bytes()))
+            };
+        }
+    }
+
+    fn partial_escape_attribute(raw: &str) -> Cow<[u8]> {
+        let bytes = raw.as_bytes();
+        let mut escaped: Vec<u8> = Vec::new();
+        let mut iter = bytes.iter().enumerate();
+        let mut pos = 0;
+        while let Some((new_pos, byte)) =
+            iter.find(|(_, &ch)| matches!(ch, b'<' | b'>' | b'&' | b'"'))
+        {
+            escaped.extend_from_slice(&bytes[pos..new_pos]);
+            match byte {
+                b'<' => escaped.extend_from_slice(b"&lt;"),
+                b'>' => escaped.extend_from_slice(b"&gt;"),
+                b'&' => escaped.extend_from_slice(b"&amp;"),
+                b'"' => escaped.extend_from_slice(b"&quot;"),
+
+                _ => unreachable!("Only '<', '>','&', '\"' are escaped"),
+            }
+            pos = new_pos + 1;
+        }
+
+        if !escaped.is_empty() {
+            if let Some(raw) = bytes.get(pos..) {
+                escaped.extend_from_slice(raw);
+            }
+
+            Cow::Owned(escaped)
+        } else {
+            Cow::Borrowed(bytes)
+        }
+    }
+
+    fn write_xml_entry(&mut self, entry: Value, top_level: bool) -> Result<(), ShellError> {
+        let entry_span = entry.span();
+        let span = entry.span();
+
+        // Allow using strings directly as content.
+        // So user can write
+        // {tag: a content: ['qwe']}
+        // instead of longer
+        // {tag: a content: [{content: 'qwe'}]}
+        if let (Value::String { val, .. }, false) = (&entry, top_level) {
+            return self.write_xml_text(val.as_str(), span);
+        }
+
+        if let Value::Record { val: record, .. } = &entry {
+            if let Some(bad_column) = Self::find_invalid_column(record) {
+                return Err(ShellError::CantConvert {
                 to_type: "XML".into(),
                 from_type: "record".into(),
                 span: entry_span,
@@ -120,304 +203,288 @@ fn to_xml_entry<W: Write>(
                     bad_column, COLUMN_TAG_NAME, COLUMN_ATTRS_NAME, COLUMN_CONTENT_NAME
                 )),
             });
-        }
-        // If key is not found it is assumed to be nothing. This way
-        // user can write a tag like {tag: a content: [...]} instead
-        // of longer {tag: a attributes: {} content: [...]}
-        let tag = record
-            .get(COLUMN_TAG_NAME)
-            .cloned()
-            .unwrap_or_else(|| Value::nothing(Span::unknown()));
-        let attrs = record
-            .get(COLUMN_ATTRS_NAME)
-            .cloned()
-            .unwrap_or_else(|| Value::nothing(Span::unknown()));
-        let content = record
-            .get(COLUMN_CONTENT_NAME)
-            .cloned()
-            .unwrap_or_else(|| Value::nothing(Span::unknown()));
+            }
+            // If key is not found it is assumed to be nothing. This way
+            // user can write a tag like {tag: a content: [...]} instead
+            // of longer {tag: a attributes: {} content: [...]}
+            let tag = record
+                .get(COLUMN_TAG_NAME)
+                .cloned()
+                .unwrap_or_else(|| Value::nothing(Span::unknown()));
+            let attrs = record
+                .get(COLUMN_ATTRS_NAME)
+                .cloned()
+                .unwrap_or_else(|| Value::nothing(Span::unknown()));
+            let content = record
+                .get(COLUMN_CONTENT_NAME)
+                .cloned()
+                .unwrap_or_else(|| Value::nothing(Span::unknown()));
 
-        let content_span = content.span();
-        let tag_span = tag.span();
-        match (tag, attrs, content) {
-            (Value::Nothing { .. }, Value::Nothing { .. }, Value::String { val, .. }) => {
-                // Strings can not appear on top level of document
-                if top_level {
+            let content_span = content.span();
+            let tag_span = tag.span();
+            match (tag, attrs, content) {
+                (Value::Nothing { .. }, Value::Nothing { .. }, Value::String { val, .. }) => {
+                    // Strings can not appear on top level of document
+                    if top_level {
+                        return Err(ShellError::CantConvert {
+                            to_type: "XML".into(),
+                            from_type: entry.get_type().to_string(),
+                            span: entry_span,
+                            help: Some("Strings can not be a root element of document".into()),
+                        });
+                    }
+                    self.write_xml_text(val.as_str(), content_span)
+                }
+                (Value::String { val: tag_name, .. }, attrs, children) => {
+                    self.write_tag_like(entry_span, tag_name, tag_span, attrs, children, top_level)
+                }
+                _ => Err(ShellError::CantConvert {
+                    to_type: "XML".into(),
+                    from_type: "record".into(),
+                    span: entry_span,
+                    help: Some("Tag missing or is not a string".into()),
+                }),
+            }
+        } else {
+            Err(ShellError::CantConvert {
+                to_type: "XML".into(),
+                from_type: entry.get_type().to_string(),
+                span: entry_span,
+                help: Some("Xml entry expected to be a record".into()),
+            })
+        }
+    }
+
+    fn find_invalid_column(record: &Record) -> Option<&String> {
+        const VALID_COLS: [&str; 3] = [COLUMN_TAG_NAME, COLUMN_ATTRS_NAME, COLUMN_CONTENT_NAME];
+        record
+            .cols
+            .iter()
+            .find(|col| !VALID_COLS.contains(&col.as_str()))
+    }
+
+    /// Convert record to tag-like entry: tag, PI, comment.
+    fn write_tag_like(
+        &mut self,
+        entry_span: Span,
+        tag: String,
+        tag_span: Span,
+        attrs: Value,
+        content: Value,
+        top_level: bool,
+    ) -> Result<(), ShellError> {
+        if tag == "!" {
+            // Comments can not appear on top level of document
+            if top_level {
+                return Err(ShellError::CantConvert {
+                    to_type: "XML".into(),
+                    from_type: "record".into(),
+                    span: entry_span,
+                    help: Some("Comments can not be a root element of document".into()),
+                });
+            }
+
+            self.write_comment(entry_span, attrs, content)
+        } else if let Some(tag) = tag.strip_prefix('?') {
+            // PIs can not appear on top level of document
+            if top_level {
+                return Err(ShellError::CantConvert {
+                    to_type: "XML".into(),
+                    from_type: Type::Record(vec![]).to_string(),
+                    span: entry_span,
+                    help: Some("PIs can not be a root element of document".into()),
+                });
+            }
+
+            let content: String = match content {
+                Value::String { val, .. } => val,
+                Value::Nothing { .. } => "".into(),
+                _ => {
                     return Err(ShellError::CantConvert {
                         to_type: "XML".into(),
-                        from_type: entry.get_type().to_string(),
-                        span: entry_span,
-                        help: Some("Strings can not be a root element of document".into()),
+                        from_type: Type::Record(vec![]).to_string(),
+                        span: content.span(),
+                        help: Some("PI content expected to be a string".into()),
                     });
                 }
-                to_xml_text(val.as_str(), content_span, writer)
+            };
+
+            self.write_processing_instruction(entry_span, tag, attrs, content)
+        } else {
+            // Allow tag to have no attributes or content for short hand input
+            // alternatives like {tag: a attributes: {} content: []}, {tag: a attribbutes: null
+            // content: null}, {tag: a}. See to_xml_entry for more
+            let attrs = match attrs {
+                Value::Record { val, .. } => val,
+                Value::Nothing { .. } => Record::new(),
+                _ => {
+                    return Err(ShellError::CantConvert {
+                        to_type: "XML".into(),
+                        from_type: attrs.get_type().to_string(),
+                        span: attrs.span(),
+                        help: Some("Tag attributes expected to be a record".into()),
+                    });
+                }
+            };
+
+            let content = match content {
+                Value::List { vals, .. } => vals,
+                Value::Nothing { .. } => Vec::new(),
+                _ => {
+                    return Err(ShellError::CantConvert {
+                        to_type: "XML".into(),
+                        from_type: content.get_type().to_string(),
+                        span: content.span(),
+                        help: Some("Tag content expected to be a list".into()),
+                    });
+                }
+            };
+
+            self.write_tag(entry_span, tag, tag_span, attrs, content)
+        }
+    }
+
+    fn write_comment(
+        &mut self,
+        entry_span: Span,
+        attrs: Value,
+        content: Value,
+    ) -> Result<(), ShellError> {
+        match (attrs, content) {
+            (Value::Nothing { .. }, Value::String { val, .. }) => {
+                // Text in comments must NOT be escaped
+                // https://www.w3.org/TR/xml/#sec-comments
+                let comment_content = BytesText::from_escaped(val.as_str());
+                self.writer
+                    .write_event(Event::Comment(comment_content))
+                    .map_err(|_| ShellError::CantConvert {
+                        to_type: "XML".to_string(),
+                        from_type: Type::Record(vec![]).to_string(),
+                        span: entry_span,
+                        help: Some("Failure writing comment to xml".into()),
+                    })
             }
-            (Value::String { val: tag_name, .. }, attrs, children) => to_tag_like(
-                entry_span, tag_name, tag_span, attrs, children, top_level, writer,
-            ),
-            _ => Err(ShellError::CantConvert {
+            (_, content) => Err(ShellError::CantConvert {
                 to_type: "XML".into(),
-                from_type: "record".into(),
+                from_type: content.get_type().to_string(),
                 span: entry_span,
-                help: Some("Tag missing or is not a string".into()),
+                help: Some("Comment expected to have string content and no attributes".into()),
             }),
         }
-    } else {
-        Err(ShellError::CantConvert {
-            to_type: "XML".into(),
-            from_type: entry.get_type().to_string(),
-            span: entry_span,
-            help: Some("Xml entry expected to be a record".into()),
-        })
     }
-}
 
-fn find_invalid_column(record: &Record) -> Option<&String> {
-    const VALID_COLS: [&str; 3] = [COLUMN_TAG_NAME, COLUMN_ATTRS_NAME, COLUMN_CONTENT_NAME];
-    record
-        .cols
-        .iter()
-        .find(|col| !VALID_COLS.contains(&col.as_str()))
-}
-
-/// Convert record to tag-like entry: tag, PI, comment.
-fn to_tag_like<W: Write>(
-    entry_span: Span,
-    tag: String,
-    tag_span: Span,
-    attrs: Value,
-    content: Value,
-    top_level: bool,
-    writer: &mut quick_xml::Writer<W>,
-) -> Result<(), ShellError> {
-    if tag == "!" {
-        // Comments can not appear on top level of document
-        if top_level {
-            return Err(ShellError::CantConvert {
-                to_type: "XML".into(),
-                from_type: "record".into(),
-                span: entry_span,
-                help: Some("Comments can not be a root element of document".into()),
-            });
-        }
-
-        to_comment(entry_span, attrs, content, writer)
-    } else if let Some(tag) = tag.strip_prefix('?') {
-        // PIs can not appear on top level of document
-        if top_level {
+    fn write_processing_instruction(
+        &mut self,
+        entry_span: Span,
+        tag: &str,
+        attrs: Value,
+        content: String,
+    ) -> Result<(), ShellError> {
+        if !matches!(attrs, Value::Nothing { .. }) {
             return Err(ShellError::CantConvert {
                 to_type: "XML".into(),
                 from_type: Type::Record(vec![]).to_string(),
                 span: entry_span,
-                help: Some("PIs can not be a root element of document".into()),
+                help: Some("PIs do not have attributes".into()),
             });
         }
 
-        let content: String = match content {
-            Value::String { val, .. } => val,
-            Value::Nothing { .. } => "".into(),
-            _ => {
-                return Err(ShellError::CantConvert {
-                    to_type: "XML".into(),
-                    from_type: Type::Record(vec![]).to_string(),
-                    span: content.span(),
-                    help: Some("PI content expected to be a string".into()),
-                });
-            }
-        };
+        let content_text = format!("{} {}", tag, content);
+        // PI content must NOT be escaped
+        // https://www.w3.org/TR/xml/#sec-pi
+        let pi_content = BytesText::from_escaped(content_text.as_str());
 
-        to_processing_instruction(entry_span, tag, attrs, content, writer)
-    } else {
-        // Allow tag to have no attributes or content for short hand input
-        // alternatives like {tag: a attributes: {} content: []}, {tag: a attribbutes: null
-        // content: null}, {tag: a}. See to_xml_entry for more
-        let attrs = match attrs {
-            Value::Record { val, .. } => val,
-            Value::Nothing { .. } => Record::new(),
-            _ => {
-                return Err(ShellError::CantConvert {
-                    to_type: "XML".into(),
-                    from_type: attrs.get_type().to_string(),
-                    span: attrs.span(),
-                    help: Some("Tag attributes expected to be a record".into()),
-                });
-            }
-        };
-
-        let content = match content {
-            Value::List { vals, .. } => vals,
-            Value::Nothing { .. } => Vec::new(),
-            _ => {
-                return Err(ShellError::CantConvert {
-                    to_type: "XML".into(),
-                    from_type: content.get_type().to_string(),
-                    span: content.span(),
-                    help: Some("Tag content expected to be a list".into()),
-                });
-            }
-        };
-
-        to_tag(entry_span, tag, tag_span, attrs, content, writer)
-    }
-}
-
-fn to_comment<W: Write>(
-    entry_span: Span,
-    attrs: Value,
-    content: Value,
-    writer: &mut quick_xml::Writer<W>,
-) -> Result<(), ShellError> {
-    match (attrs, content) {
-        (Value::Nothing { .. }, Value::String { val, .. }) => {
-            let comment_content = BytesText::new(val.as_str());
-            writer
-                .write_event(Event::Comment(comment_content))
-                .map_err(|_| ShellError::CantConvert {
-                    to_type: "XML".to_string(),
-                    from_type: Type::Record(vec![]).to_string(),
-                    span: entry_span,
-                    help: Some("Failure writing comment to xml".into()),
-                })
-        }
-        (_, content) => Err(ShellError::CantConvert {
-            to_type: "XML".into(),
-            from_type: content.get_type().to_string(),
-            span: entry_span,
-            help: Some("Comment expected to have string content and no attributes".into()),
-        }),
-    }
-}
-
-fn to_processing_instruction<W: Write>(
-    entry_span: Span,
-    tag: &str,
-    attrs: Value,
-    content: String,
-    writer: &mut quick_xml::Writer<W>,
-) -> Result<(), ShellError> {
-    if !matches!(attrs, Value::Nothing { .. }) {
-        return Err(ShellError::CantConvert {
-            to_type: "XML".into(),
-            from_type: Type::Record(vec![]).to_string(),
-            span: entry_span,
-            help: Some("PIs do not have attributes".into()),
-        });
+        self.writer
+            .write_event(Event::PI(pi_content))
+            .map_err(|_| ShellError::CantConvert {
+                to_type: "XML".to_string(),
+                from_type: Type::Record(vec![]).to_string(),
+                span: entry_span,
+                help: Some("Failure writing PI to xml".into()),
+            })
     }
 
-    let content_text = format!("{} {}", tag, content);
-    let pi_content = BytesText::new(content_text.as_str());
-    writer
-        .write_event(Event::PI(pi_content))
-        .map_err(|_| ShellError::CantConvert {
-            to_type: "XML".to_string(),
-            from_type: Type::Record(vec![]).to_string(),
-            span: entry_span,
-            help: Some("Failure writing PI to xml".into()),
-        })
-}
-
-fn to_tag<W: Write>(
-    entry_span: Span,
-    tag: String,
-    tag_span: Span,
-    attrs: Record,
-    children: Vec<Value>,
-    writer: &mut quick_xml::Writer<W>,
-) -> Result<(), ShellError> {
-    if tag.starts_with('!') || tag.starts_with('?') {
-        return Err(ShellError::CantConvert {
-            to_type: "XML".to_string(),
-            from_type: Type::Record(vec![]).to_string(),
-            span: tag_span,
-            help: Some(format!(
-                "Incorrect tag name {}, tag name can not start with ! or ?",
-                tag
-            )),
-        });
-    }
-
-    let attributes = parse_attributes(attrs)?;
-    let mut open_tag_event = BytesStart::new(tag.clone());
-    add_attributes(&mut open_tag_event, &attributes);
-
-    writer
-        .write_event(Event::Start(open_tag_event))
-        .map_err(|_| ShellError::CantConvert {
-            to_type: "XML".to_string(),
-            from_type: Type::Record(vec![]).to_string(),
-            span: entry_span,
-            help: Some("Failure writing tag to xml".into()),
-        })?;
-
-    children
-        .into_iter()
-        .try_for_each(|child| to_xml_entry(child, false, writer))?;
-
-    let close_tag_event = BytesEnd::new(tag);
-    writer
-        .write_event(Event::End(close_tag_event))
-        .map_err(|_| ShellError::CantConvert {
-            to_type: "XML".to_string(),
-            from_type: Type::Record(vec![]).to_string(),
-            span: entry_span,
-            help: Some("Failure writing tag to xml".into()),
-        })
-}
-
-fn parse_attributes(attrs: Record) -> Result<IndexMap<String, String>, ShellError> {
-    let mut h = IndexMap::new();
-    for (k, v) in attrs {
-        if let Value::String { val, .. } = v {
-            h.insert(k, val);
-        } else {
+    fn write_tag(
+        &mut self,
+        entry_span: Span,
+        tag: String,
+        tag_span: Span,
+        attrs: Record,
+        children: Vec<Value>,
+    ) -> Result<(), ShellError> {
+        if tag.starts_with('!') || tag.starts_with('?') {
             return Err(ShellError::CantConvert {
                 to_type: "XML".to_string(),
-                from_type: v.get_type().to_string(),
-                span: v.span(),
-                help: Some("Attribute value expected to be a string".into()),
+                from_type: Type::Record(vec![]).to_string(),
+                span: tag_span,
+                help: Some(format!(
+                    "Incorrect tag name {}, tag name can not start with ! or ?",
+                    tag
+                )),
             });
         }
+
+        let attributes = Self::parse_attributes(attrs)?;
+        let mut open_tag_event = BytesStart::new(tag.clone());
+        self.add_attributes(&mut open_tag_event, &attributes);
+
+        self.writer
+            .write_event(Event::Start(open_tag_event))
+            .map_err(|_| ShellError::CantConvert {
+                to_type: "XML".to_string(),
+                from_type: Type::Record(vec![]).to_string(),
+                span: entry_span,
+                help: Some("Failure writing tag to xml".into()),
+            })?;
+
+        children
+            .into_iter()
+            .try_for_each(|child| self.write_xml_entry(child, false))?;
+
+        let close_tag_event = BytesEnd::new(tag);
+        self.writer
+            .write_event(Event::End(close_tag_event))
+            .map_err(|_| ShellError::CantConvert {
+                to_type: "XML".to_string(),
+                from_type: Type::Record(vec![]).to_string(),
+                span: entry_span,
+                help: Some("Failure writing tag to xml".into()),
+            })
     }
-    Ok(h)
-}
 
-fn to_xml_text<W: Write>(
-    val: &str,
-    span: Span,
-    writer: &mut quick_xml::Writer<W>,
-) -> Result<(), ShellError> {
-    let text = Event::Text(BytesText::new(val));
-    writer
-        .write_event(text)
-        .map_err(|_| ShellError::CantConvert {
-            to_type: "XML".to_string(),
-            from_type: Type::String.to_string(),
-            span,
-            help: Some("Failure writing string to xml".into()),
-        })
-}
+    fn parse_attributes(attrs: Record) -> Result<IndexMap<String, String>, ShellError> {
+        let mut h = IndexMap::new();
+        for (k, v) in attrs {
+            if let Value::String { val, .. } = v {
+                h.insert(k, val);
+            } else {
+                return Err(ShellError::CantConvert {
+                    to_type: "XML".to_string(),
+                    from_type: v.get_type().to_string(),
+                    span: v.span(),
+                    help: Some("Attribute value expected to be a string".into()),
+                });
+            }
+        }
+        Ok(h)
+    }
 
-fn to_xml(
-    input: PipelineData,
-    head: Span,
-    indent: Option<Spanned<i64>>,
-) -> Result<PipelineData, ShellError> {
-    let mut w = indent.as_ref().map_or_else(
-        || quick_xml::Writer::new(Cursor::new(Vec::new())),
-        |p| quick_xml::Writer::new_with_indent(Cursor::new(Vec::new()), b' ', p.item as usize),
-    );
-
-    let value = input.into_value(head);
-
-    to_xml_entry(value, true, &mut w).and_then(|_| {
-        let b = w.into_inner().into_inner();
-        let s = if let Ok(s) = String::from_utf8(b) {
-            s
+    fn write_xml_text(&mut self, val: &str, span: Span) -> Result<(), ShellError> {
+        let text = Event::Text(if self.partial_escape {
+            BytesText::from_escaped(escape::partial_escape(val))
         } else {
-            return Err(ShellError::NonUtf8 { span: head });
-        };
-        Ok(Value::string(s, head).into_pipeline_data())
-    })
+            BytesText::new(val)
+        });
+
+        self.writer
+            .write_event(text)
+            .map_err(|_| ShellError::CantConvert {
+                to_type: "XML".to_string(),
+                from_type: Type::String.to_string(),
+                span,
+                help: Some("Failure writing string to xml".into()),
+            })
+    }
 }
 
 #[cfg(test)]

crates/nu-command/tests/format_conversions/xml.rs

@@ -58,3 +58,36 @@ fn to_xml_error_tag_not_string() {
 
     assert!(actual.err.contains("not a string"));
 }
+
+#[test]
+fn to_xml_partial_escape() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+            {
+                tag: a
+                attributes: { a: "'a'\\" }
+                content: [ `'"qwe\` ]
+            } | to xml --partial-escape
+        "#
+    ));
+    assert_eq!(actual.out, r#"<a a="'a'\">'"qwe\</a>"#);
+}
+
+#[test]
+fn to_xml_pi_comment_not_escaped() {
+    // PI and comment content should not be escaped
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+            {
+                tag: a
+                content: [
+                    {tag: ?qwe content: `"'<>&`}
+                    {tag: ! content: `"'<>&`}
+                ]
+            } | to xml
+        "#
+    ));
+    assert_eq!(actual.out, r#"<a><?qwe "'<>&?><!--"'<>&--></a>"#);
+}