Allow to raise application errors in ElementWriter::write_inner_content

Author: Mingun

Changelog.md

@@ -28,8 +28,11 @@ MSRV bumped to 1.56! Crate now uses Rust 2021 edition.
 - [#651]: Relax requirement for version of `arbitrary` dependency -- we're actually
   compatible with version 1.0.0 and up.
 - [#649]: Make features linkable and reference them in the docs.
+- [#619]: Allow to raise application errors in `ElementWriter::write_inner_content`
+  (and newly added `ElementWriter::write_inner_content_async` of course).
 
 [#545]: https://github.com/tafia/quick-xml/pull/545
+[#619]: https://github.com/tafia/quick-xml/issues/619
 [#635]: https://github.com/tafia/quick-xml/pull/635
 [#643]: https://github.com/tafia/quick-xml/pull/643
 [#649]: https://github.com/tafia/quick-xml/pull/646

src/writer.rs

@@ -1,9 +1,10 @@
 //! Contains high-level interface for an events-based XML emitter.
 
 use std::io::Write;
+use std::result::Result as StdResult;
 
 use crate::encoding::UTF8_BOM;
-use crate::errors::Result;
+use crate::errors::{Error, Result};
 use crate::events::{attributes::Attribute, BytesCData, BytesStart, BytesText, Event};
 
 #[cfg(feature = "async-tokio")]
@@ -105,7 +106,7 @@ impl<W> Writer<W> {
     ///
     /// # Example
     ///
-    /// ```rust
+    /// ```
     /// # use quick_xml::Result;
     /// # fn main() -> Result<()> {
     /// use quick_xml::events::{BytesStart, BytesText, Event};
@@ -127,7 +128,8 @@ impl<W> Writer<W> {
     ///
     /// // writes <tag><fruit quantity="0">apple</fruit><fruit quantity="1">orange</fruit></tag>
     /// writer.create_element("tag")
-    ///     .write_inner_content(|writer| {
+    ///     // We need to provide error type, because it is not named somewhere explicitly
+    ///     .write_inner_content::<_, Error>(|writer| {
     ///         let fruits = ["apple", "orange"];
     ///         for (quant, item) in fruits.iter().enumerate() {
     ///             writer
@@ -401,9 +403,10 @@ impl<'a, W: Write> ElementWriter<'a, W> {
     }
 
     /// Create a new scope for writing XML inside the current element.
-    pub fn write_inner_content<F>(self, closure: F) -> Result<&'a mut Writer<W>>
+    pub fn write_inner_content<F, E>(self, closure: F) -> StdResult<&'a mut Writer<W>, E>
     where
-        F: FnOnce(&mut Writer<W>) -> Result<()>,
+        F: FnOnce(&mut Writer<W>) -> StdResult<(), E>,
+        E: From<Error>,
     {
         self.writer
             .write_event(Event::Start(self.start_tag.borrow()))?;
@@ -748,7 +751,7 @@ mod indentation {
             .create_element("outer")
             .with_attribute(("attr1", "value1"))
             .with_attribute(("attr2", "value2"))
-            .write_inner_content(|writer| {
+            .write_inner_content::<_, Error>(|writer| {
                 let fruits = ["apple", "orange", "banana"];
                 for (quant, item) in fruits.iter().enumerate() {
                     writer
@@ -759,8 +762,7 @@ mod indentation {
                 writer
                     .create_element("inner")
                     .write_inner_content(|writer| {
-                        writer.create_element("empty").write_empty()?;
-                        Ok(())
+                        writer.create_element("empty").write_empty().map(|_| ())
                     })?;
 
                 Ok(())

src/writer/async_tokio.rs

@@ -1,8 +1,9 @@
 use std::future::Future;
+use std::result::Result as StdResult;
 
 use tokio::io::{AsyncWrite, AsyncWriteExt};
 
-use crate::errors::Result;
+use crate::errors::{Error, Result};
 use crate::events::{BytesCData, BytesText, Event};
 use crate::{ElementWriter, Writer};
 
@@ -252,6 +253,8 @@ impl<'a, W: AsyncWrite + Unpin> ElementWriter<'a, W> {
     /// # use quick_xml::writer::Writer;
     /// # use quick_xml::events::BytesText;
     /// # use tokio::io::AsyncWriteExt;
+    /// use quick_xml::Error;
+    ///
     /// # #[tokio::main(flavor = "current_thread")] async fn main() {
     /// let mut buffer = Vec::new();
     /// let mut tokio_buffer = tokio::io::BufWriter::new(&mut buffer);
@@ -260,7 +263,8 @@ impl<'a, W: AsyncWrite + Unpin> ElementWriter<'a, W> {
     /// writer
     ///     .create_element("outer")
     ///     .with_attributes([("attr1", "value1"), ("attr2", "value2")])
-    ///     .write_inner_content_async(|writer| async move {
+    ///     // We need to provide error type, because it is not named somewhere explicitly
+    ///     .write_inner_content_async::<_, _, Error>(|writer| async move {
     ///         let fruits = ["apple", "orange", "banana"];
     ///         for (quant, item) in fruits.iter().enumerate() {
     ///             writer
@@ -272,12 +276,11 @@ impl<'a, W: AsyncWrite + Unpin> ElementWriter<'a, W> {
     ///         writer
     ///             .create_element("inner")
     ///             .write_inner_content_async(|writer| async move {
-    ///                 writer.create_element("empty").write_empty_async().await?;
-    ///                 Ok(writer)
+    ///                 writer.create_element("empty").write_empty_async().await
     ///             })
     ///             .await?;
     ///
-    ///        Ok(writer)
+    ///         Ok(writer)
     ///     })
     ///     .await
     ///     .expect("cannot write content");
@@ -295,13 +298,14 @@ impl<'a, W: AsyncWrite + Unpin> ElementWriter<'a, W> {
     /// </outer>"#
     /// );
     /// # }
-    pub async fn write_inner_content_async<F, Fut>(
+    pub async fn write_inner_content_async<F, Fut, E>(
         mut self,
         closure: F,
-    ) -> Result<&'a mut Writer<W>>
+    ) -> StdResult<&'a mut Writer<W>, E>
     where
         F: FnOnce(&'a mut Writer<W>) -> Fut,
-        Fut: Future<Output = Result<&'a mut Writer<W>>>,
+        Fut: Future<Output = StdResult<&'a mut Writer<W>, E>>,
+        E: From<Error>,
     {
         self.writer
             .write_event_async(Event::Start(self.start_tag.borrow()))