alamb commented on PR #7843:
URL: https://github.com/apache/arrow-rs/pull/7843#issuecomment-3032501230
So I personally prefer the automatic finalize on drop behavior -- I can
understand how that behavior can cause trouble when external resources are
affected but in this case I think it makes this code much easier to use for
most cases.
If we don't finalize the object on drop of the builder, for example, the
resulting Variant object built by the builder seems to be malformed. Here is an
example
```rust
#[test]
fn test_object_list_no_finish() {
let mut builder = VariantBuilder::new();
let mut list_builder = builder.new_list();
{
let mut object_builder = list_builder.new_object();
object_builder.insert("id", 1);
object_builder.finish().unwrap();
}
{
let mut object_builder = list_builder.new_object();
object_builder.insert("id", 2);
// NOTE object_builder.finish() is not called here
}
list_builder.finish();
let (metadata, value) = builder.finish();
let variant = Variant::try_new(&metadata, &value).unwrap();
let list = variant.as_list().unwrap();
}
```
If object_builder.finish() is not called, then this line fails:
```rust
let list = variant.as_list().unwrap();
```
The error is like this (which is pretty unintuitive to me):
```
called `Result::unwrap()` on an `Err` value: InvalidArgumentError("Received
empty bytes")
thread 'builder::tests::test_object_list_no_finish' panicked at
parquet-variant/src/builder.rs:1154:59:
called `Result::unwrap()` on an `Err` value: InvalidArgumentError("Received
empty bytes")
stack backtrace:
0: __rustc::rust_begin_unwind
at
/rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/library/std/src/panicking.rs:697:5
1: core::panicking::panic_fmt
at
/rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/library/core/src/panicking.rs:75:14
2: core::result::unwrap_failed
at
/rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/library/core/src/result.rs:1732:5
3: core::result::Result<T,E>::unwrap
at
/Users/andrewlamb/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/result.rs:1137:23
4: parquet_variant::builder::tests::test_object_list_no_finish
at ./src/builder.rs:1154:23
5:
parquet_variant::builder::tests::test_object_list_no_finish::{{closure}}
at ./src/builder.rs:1133:36
6: core::ops::function::FnOnce::call_once
at
/Users/andrewlamb/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
7: core::ops::function::FnOnce::call_once
at
/rustc/6b00bc3880198600130e1cf62b8f8a93494488cc/library/core/src/ops/function.rs:250:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose
backtrace.
```
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