Adds a serializers API and improves the parser API

lib/src/io/mod.rs

@@ -1,5 +1,8 @@
-mod read;
+//! Utilities to read and write RDF graphs and datasets
+
+pub mod read;
 mod syntax;
+pub mod write;
 
 pub use self::read::DatasetParser;
 pub use self::read::GraphParser;
@@ -7,3 +10,5 @@ pub use self::syntax::DatasetSyntax;
 #[allow(deprecated)]
 pub use self::syntax::FileSyntax;
 pub use self::syntax::GraphSyntax;
+pub use self::write::DatasetSerializer;
+pub use self::write::GraphSerializer;

lib/src/io/read.rs

@@ -1,3 +1,5 @@
+//! Utilities to read RDF graphs and datasets
+
 use super::GraphSyntax;
 use crate::model::*;
 use crate::DatasetSyntax;
@@ -7,9 +9,9 @@ use rio_api::parser::{QuadsParser, TriplesParser};
 use rio_turtle::{NQuadsParser, NTriplesParser, TriGParser, TurtleParser};
 use rio_xml::RdfXmlParser;
 use std::collections::HashMap;
+use std::error::Error;
 use std::io;
 use std::io::BufRead;
-use std::iter::once;
 
 /// A reader for RDF graph serialization formats.
 ///
@@ -25,7 +27,7 @@ use std::iter::once;
 /// let file = "<http://example.com/s> <http://example.com/p> <http://example.com/o> .";
 ///
 /// let parser = GraphParser::from_syntax(GraphSyntax::NTriples);
-/// let triples = parser.read(Cursor::new(file)).collect::<Result<Vec<_>,_>>()?;
+/// let triples = parser.read_triples(Cursor::new(file))?.collect::<Result<Vec<_>,_>>()?;
 ///
 ///assert_eq!(triples.len(), 1);
 ///assert_eq!(triples[0].subject.to_string(), "<http://example.com/s>");
@@ -53,7 +55,7 @@ impl GraphParser {
     /// let file = "</s> </p> </o> .";
     ///
     /// let parser = GraphParser::from_syntax(GraphSyntax::Turtle).with_base_iri("http://example.com")?;
-    /// let triples = parser.read(Cursor::new(file)).collect::<Result<Vec<_>,_>>()?;
+    /// let triples = parser.read_triples(Cursor::new(file))?.collect::<Result<Vec<_>,_>>()?;
     ///
     ///assert_eq!(triples.len(), 1);
     ///assert_eq!(triples[0].subject.to_string(), "<http://example.com/s>");
@@ -65,47 +67,98 @@ impl GraphParser {
     }
 
     /// Executes the parsing itself
-    pub fn read<'a>(
-        &self,
-        reader: impl BufRead + 'a,
-    ) -> impl Iterator<Item = Result<Triple, io::Error>> + 'a {
-        match self.parse(reader) {
-            Ok(iter) => iter,
-            Err(error) => Box::new(once(Err(error))),
-        }
+    pub fn read_triples<R: BufRead>(&self, reader: R) -> Result<TripleReader<R>, io::Error> {
+        //TODO: drop the error when possible
+        Ok(TripleReader {
+            mapper: RioMapper::default(),
+            parser: match self.syntax {
+                GraphSyntax::NTriples => {
+                    TripleReaderKind::NTriples(NTriplesParser::new(reader).map_err(invalid_input)?)
+                }
+                GraphSyntax::Turtle => TripleReaderKind::Turtle(
+                    TurtleParser::new(reader, &self.base_iri).map_err(invalid_input)?,
+                ),
+                GraphSyntax::RdfXml => TripleReaderKind::RdfXml(
+                    RdfXmlParser::new(reader, &self.base_iri).map_err(invalid_input)?,
+                ),
+            },
+            buffer: Vec::new(),
+        })
     }
+}
 
-    fn parse<'a>(
-        &self,
-        reader: impl BufRead + 'a,
-    ) -> Result<Box<dyn Iterator<Item = Result<Triple, io::Error>> + 'a>, io::Error> {
-        Ok(match self.syntax {
-            GraphSyntax::NTriples => {
-                Box::new(self.parse_from_triple_parser(NTriplesParser::new(reader))?)
-            }
-            GraphSyntax::Turtle => {
-                Box::new(self.parse_from_triple_parser(TurtleParser::new(reader, &self.base_iri))?)
+/// Allows reading triples.
+/// Could be built using a `GraphParser`.
+///
+/// ```
+/// use oxigraph::io::{GraphSyntax, GraphParser};
+/// use std::io::Cursor;
+///
+/// let file = "<http://example.com/s> <http://example.com/p> <http://example.com/o> .";
+///
+/// let parser = GraphParser::from_syntax(GraphSyntax::NTriples);
+/// let triples = parser.read_triples(Cursor::new(file))?.collect::<Result<Vec<_>,_>>()?;
+///
+///assert_eq!(triples.len(), 1);
+///assert_eq!(triples[0].subject.to_string(), "<http://example.com/s>");
+/// # std::io::Result::Ok(())
+/// ```
+#[must_use]
+pub struct TripleReader<R: BufRead> {
+    mapper: RioMapper,
+    parser: TripleReaderKind<R>,
+    buffer: Vec<Triple>,
+}
+
+enum TripleReaderKind<R: BufRead> {
+    NTriples(NTriplesParser<R>),
+    Turtle(TurtleParser<R>),
+    RdfXml(RdfXmlParser<R>),
+}
+
+impl<R: BufRead> Iterator for TripleReader<R> {
+    type Item = Result<Triple, io::Error>;
+
+    fn next(&mut self) -> Option<Result<Triple, io::Error>> {
+        loop {
+            if let Some(r) = self.buffer.pop() {
+                return Some(Ok(r));
             }
-            GraphSyntax::RdfXml => {
-                Box::new(self.parse_from_triple_parser(RdfXmlParser::new(reader, &self.base_iri))?)
+
+            if let Err(error) = match &mut self.parser {
+                TripleReaderKind::NTriples(parser) => {
+                    Self::read(parser, &mut self.buffer, &mut self.mapper, invalid_data)
+                }
+                TripleReaderKind::Turtle(parser) => {
+                    Self::read(parser, &mut self.buffer, &mut self.mapper, invalid_data)
+                }
+                TripleReaderKind::RdfXml(parser) => {
+                    Self::read(parser, &mut self.buffer, &mut self.mapper, invalid_data)
+                }
+            }? {
+                return Some(Err(error));
             }
-        })
+        }
     }
+}
 
-    fn parse_from_triple_parser<P: TriplesParser>(
-        &self,
-        parser: Result<P, P::Error>,
-    ) -> Result<impl Iterator<Item = Result<Triple, io::Error>>, io::Error>
-    where
-        P::Error: Send + Sync + 'static,
-    {
-        let parser = parser.map_err(|e| io::Error::new(io::ErrorKind::InvalidInput, e))?;
-        let mut mapper = RioMapper::default();
-        Ok(parser
-            .into_iter(move |t| Ok(mapper.triple(&t)))
-            .map(|e: Result<_, P::Error>| {
-                e.map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
-            }))
+impl<R: BufRead> TripleReader<R> {
+    fn read<P: TriplesParser>(
+        parser: &mut P,
+        buffer: &mut Vec<Triple>,
+        mapper: &mut RioMapper,
+        error: impl Fn(P::Error) -> io::Error,
+    ) -> Option<Result<(), io::Error>> {
+        if parser.is_end() {
+            None
+        } else if let Err(e) = parser.parse_step(&mut |t| {
+            buffer.push(mapper.triple(&t));
+            Ok(())
+        }) {
+            Some(Err(error(e)))
+        } else {
+            Some(Ok(()))
+        }
     }
 }
 
@@ -122,7 +175,7 @@ impl GraphParser {
 /// let file = "<http://example.com/s> <http://example.com/p> <http://example.com/o> <http://example.com/g> .";
 ///
 /// let parser = DatasetParser::from_syntax(DatasetSyntax::NQuads);
-/// let quads = parser.read(Cursor::new(file)).collect::<Result<Vec<_>,_>>()?;
+/// let quads = parser.read_quads(Cursor::new(file))?.collect::<Result<Vec<_>,_>>()?;
 ///
 ///assert_eq!(quads.len(), 1);
 ///assert_eq!(quads[0].subject.to_string(), "<http://example.com/s>");
@@ -150,7 +203,7 @@ impl DatasetParser {
     /// let file = "<g> { </s> </p> </o> }";
     ///
     /// let parser = DatasetParser::from_syntax(DatasetSyntax::TriG).with_base_iri("http://example.com")?;
-    /// let triples = parser.read(Cursor::new(file)).collect::<Result<Vec<_>,_>>()?;
+    /// let triples = parser.read_quads(Cursor::new(file))?.collect::<Result<Vec<_>,_>>()?;
     ///
     ///assert_eq!(triples.len(), 1);
     ///assert_eq!(triples[0].subject.to_string(), "<http://example.com/s>");
@@ -162,44 +215,91 @@ impl DatasetParser {
     }
 
     /// Executes the parsing itself
-    pub fn read<'a>(
-        &self,
-        reader: impl BufRead + 'a,
-    ) -> impl Iterator<Item = Result<Quad, io::Error>> + 'a {
-        match self.parse(reader) {
-            Ok(iter) => iter,
-            Err(error) => Box::new(once(Err(error))),
-        }
+    pub fn read_quads<R: BufRead>(&self, reader: R) -> Result<QuadReader<R>, io::Error> {
+        //TODO: drop the error when possible
+        Ok(QuadReader {
+            mapper: RioMapper::default(),
+            parser: match self.syntax {
+                DatasetSyntax::NQuads => {
+                    QuadReaderKind::NQuads(NQuadsParser::new(reader).map_err(invalid_input)?)
+                }
+                DatasetSyntax::TriG => QuadReaderKind::TriG(
+                    TriGParser::new(reader, &self.base_iri).map_err(invalid_input)?,
+                ),
+            },
+            buffer: Vec::new(),
+        })
     }
+}
 
-    fn parse<'a>(
-        &self,
-        reader: impl BufRead + 'a,
-    ) -> Result<Box<dyn Iterator<Item = Result<Quad, io::Error>> + 'a>, io::Error> {
-        Ok(match self.syntax {
-            DatasetSyntax::NQuads => {
-                Box::new(self.parse_from_quad_parser(NQuadsParser::new(reader))?)
+/// Allows reading quads.
+/// Could be built using a `DatasetParser`.
+///
+/// ```
+/// use oxigraph::io::{DatasetSyntax, DatasetParser};
+/// use std::io::Cursor;
+///
+/// let file = "<http://example.com/s> <http://example.com/p> <http://example.com/o> <http://example.com/g> .";
+///
+/// let parser = DatasetParser::from_syntax(DatasetSyntax::NQuads);
+/// let quads = parser.read_quads(Cursor::new(file))?.collect::<Result<Vec<_>,_>>()?;
+///
+///assert_eq!(quads.len(), 1);
+///assert_eq!(quads[0].subject.to_string(), "<http://example.com/s>");
+/// # std::io::Result::Ok(())
+/// ```
+#[must_use]
+pub struct QuadReader<R: BufRead> {
+    mapper: RioMapper,
+    parser: QuadReaderKind<R>,
+    buffer: Vec<Quad>,
+}
+
+enum QuadReaderKind<R: BufRead> {
+    NQuads(NQuadsParser<R>),
+    TriG(TriGParser<R>),
+}
+
+impl<R: BufRead> Iterator for QuadReader<R> {
+    type Item = Result<Quad, io::Error>;
+
+    fn next(&mut self) -> Option<Result<Quad, io::Error>> {
+        loop {
+            if let Some(r) = self.buffer.pop() {
+                return Some(Ok(r));
             }
-            DatasetSyntax::TriG => {
-                Box::new(self.parse_from_quad_parser(TriGParser::new(reader, &self.base_iri))?)
+
+            if let Err(error) = match &mut self.parser {
+                QuadReaderKind::NQuads(parser) => {
+                    Self::read(parser, &mut self.buffer, &mut self.mapper, invalid_data)
+                }
+                QuadReaderKind::TriG(parser) => {
+                    Self::read(parser, &mut self.buffer, &mut self.mapper, invalid_data)
+                }
+            }? {
+                return Some(Err(error));
             }
-        })
+        }
     }
+}
 
-    fn parse_from_quad_parser<P: QuadsParser>(
-        &self,
-        parser: Result<P, P::Error>,
-    ) -> Result<impl Iterator<Item = Result<Quad, io::Error>>, io::Error>
-    where
-        P::Error: Send + Sync + 'static,
-    {
-        let parser = parser.map_err(|e| io::Error::new(io::ErrorKind::InvalidInput, e))?;
-        let mut mapper = RioMapper::default();
-        Ok(parser
-            .into_iter(move |q| Ok(mapper.quad(&q)))
-            .map(|e: Result<_, P::Error>| {
-                e.map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
-            }))
+impl<R: BufRead> QuadReader<R> {
+    fn read<P: QuadsParser>(
+        parser: &mut P,
+        buffer: &mut Vec<Quad>,
+        mapper: &mut RioMapper,
+        error: impl Fn(P::Error) -> io::Error,
+    ) -> Option<Result<(), io::Error>> {
+        if parser.is_end() {
+            None
+        } else if let Err(e) = parser.parse_step(&mut |t| {
+            buffer.push(mapper.quad(&t));
+            Ok(())
+        }) {
+            Some(Err(error(e)))
+        } else {
+            Some(Ok(()))
+        }
     }
 }
 
@@ -272,3 +372,11 @@ impl<'a> RioMapper {
         }
     }
 }
+
+fn invalid_input(error: impl Error + Send + Sync + 'static) -> io::Error {
+    io::Error::new(io::ErrorKind::InvalidInput, error)
+}
+
+fn invalid_data(error: impl Error + Send + Sync + 'static) -> io::Error {
+    io::Error::new(io::ErrorKind::InvalidData, error) //TODO: drop
+}

lib/src/io/write.rs

@@ -0,0 +1,211 @@
+//! Utilities to write RDF graphs and datasets
+
+use super::GraphSyntax;
+use crate::model::*;
+use crate::DatasetSyntax;
+use rio_api::formatter::{QuadsFormatter, TriplesFormatter};
+use rio_turtle::{NQuadsFormatter, NTriplesFormatter, TriGFormatter, TurtleFormatter};
+use rio_xml::{RdfXmlError, RdfXmlFormatter};
+use std::io;
+use std::io::Write;
+
+/// A serializer for RDF graph serialization formats.
+///
+/// It currently supports the following formats:
+/// * [N-Triples](https://www.w3.org/TR/n-triples/) (`GraphSyntax::NTriples`)
+/// * [Turtle](https://www.w3.org/TR/turtle/) (`GraphSyntax::Turtle`)
+/// * [RDF XML](https://www.w3.org/TR/rdf-syntax-grammar/) (`GraphSyntax::RdfXml`)
+///
+/// ```
+/// use oxigraph::io::{GraphSyntax, GraphSerializer};
+/// use oxigraph::model::*;
+///
+/// let mut buffer = Vec::new();
+/// let mut writer = GraphSerializer::from_syntax(GraphSyntax::NTriples).triple_writer(&mut buffer)?;
+/// writer.write(&Triple {
+///    subject: NamedNode::new("http://example.com/s")?.into(),
+///    predicate: NamedNode::new("http://example.com/p")?,
+///    object: NamedNode::new("http://example.com/o")?.into()
+/// })?;
+/// writer.finish()?;
+///
+///assert_eq!(buffer.as_slice(), "<http://example.com/s> <http://example.com/p> <http://example.com/o> .\n".as_bytes());
+/// # oxigraph::Result::Ok(())
+/// ```
+#[allow(missing_copy_implementations)]
+pub struct GraphSerializer {
+    syntax: GraphSyntax,
+}
+
+impl GraphSerializer {
+    pub fn from_syntax(syntax: GraphSyntax) -> Self {
+        Self { syntax }
+    }
+
+    /// Returns a `TripleWriter` allowing writing triples into the given `Write` implementation
+    pub fn triple_writer<W: Write>(&self, writer: W) -> Result<TripleWriter<W>, io::Error> {
+        Ok(TripleWriter {
+            formatter: match self.syntax {
+                GraphSyntax::NTriples => TripleWriterKind::NTriples(NTriplesFormatter::new(writer)),
+                GraphSyntax::Turtle => TripleWriterKind::Turtle(TurtleFormatter::new(writer)),
+                GraphSyntax::RdfXml => {
+                    TripleWriterKind::RdfXml(RdfXmlFormatter::new(writer).map_err(map_xml_err)?)
+                }
+            },
+        })
+    }
+}
+
+/// Allows writing triples.
+/// Could be built using a `GraphSerializer`.
+///
+/// Warning: Do not forget to run the `finish` method to properly write the last bytes of the file.
+///
+/// ```
+/// use oxigraph::io::{GraphSyntax, GraphSerializer};
+/// use oxigraph::model::*;
+///
+/// let mut buffer = Vec::new();
+/// let mut writer = GraphSerializer::from_syntax(GraphSyntax::NTriples).triple_writer(&mut buffer)?;
+/// writer.write(&Triple {
+///    subject: NamedNode::new("http://example.com/s")?.into(),
+///    predicate: NamedNode::new("http://example.com/p")?,
+///    object: NamedNode::new("http://example.com/o")?.into()
+/// })?;
+/// writer.finish()?;
+///
+///assert_eq!(buffer.as_slice(), "<http://example.com/s> <http://example.com/p> <http://example.com/o> .\n".as_bytes());
+/// # oxigraph::Result::Ok(())
+/// ```
+#[must_use]
+pub struct TripleWriter<W: Write> {
+    formatter: TripleWriterKind<W>,
+}
+
+enum TripleWriterKind<W: Write> {
+    NTriples(NTriplesFormatter<W>),
+    Turtle(TurtleFormatter<W>),
+    RdfXml(RdfXmlFormatter<W>),
+}
+
+impl<W: Write> TripleWriter<W> {
+    pub fn write(&mut self, triple: &Triple) -> Result<(), io::Error> {
+        match &mut self.formatter {
+            TripleWriterKind::NTriples(formatter) => formatter.format(&triple.into())?,
+            TripleWriterKind::Turtle(formatter) => formatter.format(&triple.into())?,
+            TripleWriterKind::RdfXml(formatter) => {
+                formatter.format(&triple.into()).map_err(map_xml_err)?
+            }
+        }
+        Ok(())
+    }
+
+    /// Writes the last bytes of the file
+    pub fn finish(self) -> Result<(), io::Error> {
+        match self.formatter {
+            TripleWriterKind::NTriples(formatter) => formatter.finish(),
+            TripleWriterKind::Turtle(formatter) => formatter.finish()?,
+            TripleWriterKind::RdfXml(formatter) => formatter.finish().map_err(map_xml_err)?,
+        };
+        Ok(())
+    }
+}
+
+/// A serializer for RDF graph serialization formats.
+///
+/// It currently supports the following formats:
+/// * [N-Quads](https://www.w3.org/TR/n-quads/) (`DatasetSyntax::NQuads`)
+/// * [TriG](https://www.w3.org/TR/trig/) (`DatasetSyntax::TriG`)
+///
+/// ```
+/// use oxigraph::io::{DatasetSyntax, DatasetSerializer};
+/// use oxigraph::model::*;
+///
+/// let mut buffer = Vec::new();
+/// let mut writer = DatasetSerializer::from_syntax(DatasetSyntax::NQuads).quad_writer(&mut buffer)?;
+/// writer.write(&Quad {
+///    subject: NamedNode::new("http://example.com/s")?.into(),
+///    predicate: NamedNode::new("http://example.com/p")?,
+///    object: NamedNode::new("http://example.com/o")?.into(),
+///    graph_name: NamedNode::new("http://example.com/g")?.into(),
+/// })?;
+/// writer.finish()?;
+///
+///assert_eq!(buffer.as_slice(), "<http://example.com/s> <http://example.com/p> <http://example.com/o> <http://example.com/g> .\n".as_bytes());
+/// # oxigraph::Result::Ok(())
+/// ```
+#[allow(missing_copy_implementations)]
+pub struct DatasetSerializer {
+    syntax: DatasetSyntax,
+}
+
+impl DatasetSerializer {
+    pub fn from_syntax(syntax: DatasetSyntax) -> Self {
+        Self { syntax }
+    }
+
+    /// Returns a `QuadWriter` allowing writing triples into the given `Write` implementation
+    pub fn quad_writer<W: Write>(&self, writer: W) -> Result<QuadWriter<W>, io::Error> {
+        Ok(QuadWriter {
+            formatter: match self.syntax {
+                DatasetSyntax::NQuads => QuadWriterKind::NQuads(NQuadsFormatter::new(writer)),
+                DatasetSyntax::TriG => QuadWriterKind::TriG(TriGFormatter::new(writer)),
+            },
+        })
+    }
+}
+
+/// Allows writing triples.
+/// Could be built using a `DatasetSerializer`.
+///
+/// Warning: Do not forget to run the `finish` method to properly write the last bytes of the file.
+///
+/// ```
+/// use oxigraph::io::{DatasetSyntax, DatasetSerializer};
+/// use oxigraph::model::*;
+///
+/// let mut buffer = Vec::new();
+/// let mut writer = DatasetSerializer::from_syntax(DatasetSyntax::NQuads).quad_writer(&mut buffer)?;
+/// writer.write(&Quad {
+///    subject: NamedNode::new("http://example.com/s")?.into(),
+///    predicate: NamedNode::new("http://example.com/p")?,
+///    object: NamedNode::new("http://example.com/o")?.into(),
+///    graph_name: NamedNode::new("http://example.com/g")?.into(),
+/// })?;
+/// writer.finish()?;
+///
+///assert_eq!(buffer.as_slice(), "<http://example.com/s> <http://example.com/p> <http://example.com/o> <http://example.com/g> .\n".as_bytes());
+/// # oxigraph::Result::Ok(())
+/// ```
+#[must_use]
+pub struct QuadWriter<W: Write> {
+    formatter: QuadWriterKind<W>,
+}
+
+enum QuadWriterKind<W: Write> {
+    NQuads(NQuadsFormatter<W>),
+    TriG(TriGFormatter<W>),
+}
+
+impl<W: Write> QuadWriter<W> {
+    pub fn write(&mut self, triple: &Quad) -> Result<(), io::Error> {
+        match &mut self.formatter {
+            QuadWriterKind::NQuads(formatter) => formatter.format(&triple.into())?,
+            QuadWriterKind::TriG(formatter) => formatter.format(&triple.into())?,
+        }
+        Ok(())
+    }
+
+    /// Writes the last bytes of the file
+    pub fn finish(self) -> Result<(), io::Error> {
+        match self.formatter {
+            QuadWriterKind::NQuads(formatter) => formatter.finish(),
+            QuadWriterKind::TriG(formatter) => formatter.finish()?,
+        };
+        Ok(())
+    }
+}
+
+fn map_xml_err(e: RdfXmlError) -> io::Error {
+    io::Error::new(io::ErrorKind::Other, e) //TODO: drop
+}

lib/src/sparql/model.rs

@@ -1,3 +1,4 @@
+use crate::io::GraphSerializer;
 #[allow(deprecated)]
 use crate::io::{FileSyntax, GraphSyntax};
 use crate::model::*;
@@ -5,9 +6,6 @@ use crate::sparql::json_results::write_json_results;
 use crate::sparql::xml_results::{read_xml_results, write_xml_results};
 use crate::{Error, Result};
 use rand::random;
-use rio_api::formatter::TriplesFormatter;
-use rio_turtle::{NTriplesFormatter, TurtleFormatter};
-use rio_xml::RdfXmlFormatter;
 use std::fmt;
 use std::io::{BufRead, Write};
 use std::rc::Rc;
@@ -80,29 +78,11 @@ impl QueryResult {
     /// ```
     pub fn write_graph(self, write: impl Write, syntax: GraphSyntax) -> Result<()> {
         if let QueryResult::Graph(triples) = self {
-            match syntax {
-                GraphSyntax::NTriples => {
-                    let mut formatter = NTriplesFormatter::new(write);
-                    for triple in triples {
-                        formatter.format(&(&triple?).into())?;
-                    }
-                    formatter.finish();
-                }
-                GraphSyntax::Turtle => {
-                    let mut formatter = TurtleFormatter::new(write);
-                    for triple in triples {
-                        formatter.format(&(&triple?).into())?;
-                    }
-                    formatter.finish()?;
-                }
-                GraphSyntax::RdfXml => {
-                    let mut formatter = RdfXmlFormatter::new(write)?;
-                    for triple in triples {
-                        formatter.format(&(&triple?).into())?;
-                    }
-                    formatter.finish()?;
-                }
+            let mut writer = GraphSerializer::from_syntax(syntax).triple_writer(write)?;
+            for triple in triples {
+                writer.write(&triple?)?;
             }
+            writer.finish()?;
             Ok(())
         } else {
             Err(Error::msg(

lib/src/store/mod.rs

@@ -139,7 +139,7 @@ fn dump_graph(
 }
 
 fn map_xml_err(e: RdfXmlError) -> io::Error {
-    io::Error::new(io::ErrorKind::Other, e)
+    io::Error::new(io::ErrorKind::Other, e) // TODO: drop
 }
 
 fn load_dataset<S: WritableEncodedStore>(