Test case which shows empty list of struct cannot be written

parquet/tests/array_struct_bug.rs

@@ -0,0 +1,66 @@
+use std::{
+    fs,
+    io::{prelude::*, SeekFrom},
+    sync::Arc,
+};
+use std::env;
+use std::fs::File;
+
+use arrow::datatypes::{DataType, Field, Schema};
+use parquet::{
+    basic::Repetition, basic::Type, file::properties::WriterProperties,
+    file::writer::SerializedFileWriter, schema::types,
+};
+use parquet::arrow::ArrowWriter;
+use parquet::basic::ConvertedType;
+use parquet::file::writer::TryClone;
+use parquet::util::cursor::InMemoryWriteableCursor;
+use serde_json::Value;
+use arrow::json::reader::Decoder;
+use arrow::record_batch::RecordBatch;
+use parquet::errors::ParquetError;
+
+#[test]
+fn array_struct_bug() {
+    let struct_f = Field::new("element", DataType::Struct(vec![
+        Field::new("a", DataType::Utf8, true),
+        Field::new("b", DataType::Utf8, true),
+    ]), true);
+    let list_struct_f = Field::new("list", DataType::List(Box::new(struct_f)), true);
+    let schema = Arc::new(Schema::new(vec![list_struct_f]));
+
+    let cursor = InMemoryWriteableCursor::default();
+    let mut arrow_writer = ArrowWriter::try_new(
+        cursor.clone(),
+        schema.clone(),
+        None,
+    ).unwrap();
+
+    let json1: Value = serde_json::from_str(r#"{"list": [{"a": 1, "b": 2}]}"#).unwrap();
+    let json2: Value = serde_json::from_str(r#"{"list": null}"#).unwrap();
+    let json3: Value = serde_json::from_str(r#"{"list": []}"#).unwrap();
+
+    // successful, list non empty
+    arrow_writer
+        .write(&batch_of(schema.clone(), json1))
+        .unwrap();
+
+    // failed, list is null
+    let result2 = arrow_writer
+        .write(&batch_of(schema.clone(), json2));
+    println!("Result 2 {:?}", result2);
+
+    // failed, list is empty
+    let result3 = arrow_writer
+        .write(&batch_of(schema.clone(), json3));
+    println!("Result 3 {:?}", result2);
+
+    result2.unwrap();
+    result3.unwrap();
+}
+
+pub fn batch_of(schema: Arc<Schema>, json: Value) -> RecordBatch {
+    let decoder = Decoder::new(schema.clone(), 1, None);
+    let mut iter = std::iter::once(Ok(json));
+    decoder.next_batch(&mut iter).unwrap().unwrap()
+}