jhorstmann commented on a change in pull request #1205:
URL: https://github.com/apache/arrow-rs/pull/1205#discussion_r787618284
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File path: arrow/src/json/writer.rs
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@@ -178,31 +178,29 @@ pub fn array_to_json_array(array: &ArrayRef) ->
Vec<Value> {
DataType::UInt64 => primitive_array_to_json::<UInt64Type>(array),
DataType::Float32 => primitive_array_to_json::<Float32Type>(array),
DataType::Float64 => primitive_array_to_json::<Float64Type>(array),
- DataType::List(_) => as_list_array(array)
+ DataType::List(_) => Ok(as_list_array(array)
.iter()
.map(|maybe_value| match maybe_value {
- Some(v) => Value::Array(array_to_json_array(&v)),
+ Some(v) => Value::Array(array_to_json_array(&v).unwrap()),
Review comment:
Since this is inside a closure, that closure needs to have a return type
of `Result` in order to use the `?` operator. You can achieve that by wrapping
the Value in `Ok` like this:
```
DataType::List(_) => as_list_array(array)
.iter()
.map(|maybe_value| {
match maybe_value {
Some(v) => Ok(Value::Array(array_to_json_array(&v)?)),
None => Ok(Value::Null),
}})
.collect(),
```
The `collect` at the end is able to create a `Result<Vec<X>>` from that
`Iterator<Result<X>>`. The type is inferred based on the method return type.
Often you would have to specify that explicitly like
`.collect::<Result<Vec<_>>()`.
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