Adds write_value to ElementWriter

src/element/writer.rs

@@ -12,10 +12,17 @@ pub use TextKind::*;
 
 /// Serializes [`Element`] instances into some kind of output sink.
 pub trait ElementWriter {
-    /// Serializes a single [`Element`] as a top-level value.
+    /// Serializes a single [`Element`] at the current depth of the writer.
     fn write_element(&mut self, element: &Element) -> IonResult<()>;
 
-    /// Serializes a collection of [`Element`] as a series of top-level values.
+    /// Serializes a single [`Value`] at the current depth of the writer.
+    // TODO: consider extracting this to a ValueWriter trait.
+    fn write_value(&mut self, value: &Value) -> IonResult<()>;
+
+    /// Serializes a collection of [`Element`].
+    ///
+    /// Most commonly used to serialize a series of top-level values, but can be used to write
+    /// [`Element`]s to an Ion `list` or `sexp` as well.
     ///
     /// This will return [`Err`] if writing any element causes a failure.
     fn write_elements<'a, I: IntoIterator<Item = &'a Element>>(
@@ -35,8 +42,11 @@ where
 {
     fn write_element(&mut self, element: &Element) -> IonResult<()> {
         self.set_annotations(element.annotations());
+        self.write_value(element.value())
+    }
 
-        match element.value() {
+    fn write_value(&mut self, value: &Value) -> IonResult<()> {
+        match value {
             Value::Null(ion_type) => self.write_null(*ion_type),
             Value::Int(i) => self.write_int(i),
             Value::Float(f) => {
@@ -96,11 +106,11 @@ pub enum Format {
 #[cfg(test)]
 mod tests {
     use crate::element::writer::ElementWriter;
-    use crate::element::Element;
+    use crate::element::{Element, List};
     use crate::ion_data::IonEq;
     use crate::text::text_writer::TextWriterBuilder;
 
-    use crate::{IonResult, IonWriter};
+    use crate::{IonResult, IonType, IonWriter};
     use nom::AsBytes;
 
     #[test]
@@ -109,7 +119,7 @@ mod tests {
         let mut writer = TextWriterBuilder::default().build(&mut buffer)?;
 
         let ion = r#"
-            null true 0 1e0 2.0 2022T foo "bar" (foo bar baz) [foo, bar, baz] {foo: true, bar: false}
+            null true 0 1e0 2.0 2022T foo "bar" (foo bar baz) [foo, bar, baz] {foo: true, bar: false} annotated::value
         "#;
         let expected_elements = Element::read_all(ion.as_bytes())?;
         writer.write_elements(&expected_elements)?;
@@ -118,4 +128,42 @@ mod tests {
         assert!(expected_elements.ion_eq(&actual_elements));
         Ok(())
     }
+
+    #[test]
+    fn write_nested_element() -> IonResult<()> {
+        let mut buffer = Vec::new();
+        let mut writer = TextWriterBuilder::default().build(&mut buffer)?;
+
+        let ion = r#"
+            null true 0 1e0 2.0 2022T foo "bar" (foo bar baz) [foo, bar, baz] {foo: true, bar: false} annotated::value
+        "#;
+        let expected_list_elements = Element::read_all(ion.as_bytes())?;
+        writer.step_in(IonType::List)?;
+        writer.write_elements(&expected_list_elements)?;
+        writer.step_out()?;
+        writer.flush()?;
+        // This should be an Ion List containing all of the above elements.
+        let actual_list = Element::read_one(writer.output().as_bytes())?;
+        let expected_list: Element = List::from(expected_list_elements).into();
+        assert!(expected_list.ion_eq(&actual_list));
+        Ok(())
+    }
+
+    #[test]
+    fn write_value() -> IonResult<()> {
+        let mut buffer = Vec::new();
+        let mut writer = TextWriterBuilder::default().build(&mut buffer)?;
+
+        let ion = r#"
+            null true 0 1e0 2.0 2022T foo "bar" (foo bar baz) [foo, bar, baz] {foo: true, bar: false}
+        "#;
+        let expected_elements = Element::read_all(ion.as_bytes())?;
+        for e in &expected_elements {
+            writer.write_value(e.value())?;
+        }
+        writer.flush()?;
+        let actual_elements = Element::read_all(writer.output().as_bytes())?;
+        assert!(expected_elements.ion_eq(&actual_elements));
+        Ok(())
+    }
 }