ARROW-10390: [Rust][Parquet] Ensure it is possible to create custom parquet writers

rust/parquet/src/file/writer.rs

@@ -38,7 +38,7 @@ use crate::file::{
     statistics::to_thrift as statistics_to_thrift, FOOTER_SIZE, PARQUET_MAGIC,
 };
 use crate::schema::types::{self, SchemaDescPtr, SchemaDescriptor, TypePtr};
-use crate::util::io::{FileSink, Position, TryClone};
+use crate::util::io::{FileSink, Position};
 
 // ----------------------------------------------------------------------
 // APIs for file & row group writers
@@ -114,6 +114,7 @@ pub trait RowGroupWriter {
 // ----------------------------------------------------------------------
 // Serialized impl for file & row group writers
 
+pub use crate::util::io::TryClone;
 pub trait ParquetWriter: Write + Seek + TryClone {}
 impl<T: Write + Seek + TryClone> ParquetWriter for T {}
 

rust/parquet/tests/custom_writer.rs

@@ -0,0 +1,83 @@
+use std::fs::File;
+use std::{
+    fs,
+    io::{prelude::*, SeekFrom},
+    rc::Rc,
+};
+
+use parquet::file::writer::TryClone;
+use parquet::{
+    basic::Repetition, basic::Type, file::properties::WriterProperties,
+    file::writer::SerializedFileWriter, schema::types,
+};
+use std::env;
+
+// Test creating some sort of custom writer to ensure the
+// appropriate traits are exposed
+struct CustomWriter {
+    file: File,
+}
+
+impl Write for CustomWriter {
+    fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+        self.file.write(buf)
+    }
+    fn flush(&mut self) -> std::io::Result<()> {
+        self.file.flush()
+    }
+}
+
+impl Seek for CustomWriter {
+    fn seek(&mut self, pos: SeekFrom) -> std::io::Result<u64> {
+        self.file.seek(pos)
+    }
+}
+
+impl TryClone for CustomWriter {
+    fn try_clone(&self) -> std::io::Result<Self> {
+        use std::io::{Error, ErrorKind};
+        Err(Error::new(ErrorKind::Other, "Clone not supported"))
+    }
+}
+
+#[test]
+fn test_custom_writer() {
+    let schema = Rc::new(
+        types::Type::group_type_builder("schema")
+            .with_fields(&mut vec![Rc::new(
+                types::Type::primitive_type_builder("col1", Type::INT32)
+                    .with_repetition(Repetition::REQUIRED)
+                    .build()
+                    .unwrap(),
+            )])
+            .build()
+            .unwrap(),
+    );
+    let props = Rc::new(WriterProperties::builder().build());
+
+    let file = get_temp_file("test_custom_file_writer");
+    let test_file = file.try_clone().unwrap();
+
+    let writer = CustomWriter { file };
+
+    // test is that this file can be created
+    let file_writer = SerializedFileWriter::new(writer, schema, props).unwrap();
+    std::mem::drop(file_writer);
+
+    // ensure the file now exists and has non zero size
+    let metadata = test_file.metadata().unwrap();
+    assert!(metadata.len() > 0);
+}
+
+/// Returns file handle for a temp file in 'target' directory with a provided content
+fn get_temp_file(file_name: &str) -> fs::File {
+    // build tmp path to a file in "target/debug/testdata"
+    let mut path_buf = env::current_dir().unwrap();
+    path_buf.push("target");
+    path_buf.push("debug");
+    path_buf.push("testdata");
+    fs::create_dir_all(&path_buf).unwrap();
+    path_buf.push(file_name);
+
+    File::create(path_buf).unwrap()
+}