stuartcarnie commented on code in PR #3887:
URL: https://github.com/apache/arrow-rs/pull/3887#discussion_r1142905798
##########
arrow-flight/src/sql/mod.rs:
##########
@@ -71,22 +72,60 @@ pub trait ProstMessageExt: prost::Message + Default {
fn as_any(&self) -> Any;
}
+/// Macro to coerce a token to an item, specifically
+/// to build the `Commands` enum.
+///
+/// See: <https://danielkeep.github.io/tlborm/book/blk-ast-coercion.html>
+macro_rules! as_item {
+ ($i:item) => {
+ $i
+ };
+}
+
macro_rules! prost_message_ext {
- ($($name:ty,)*) => {
- $(
- impl ProstMessageExt for $name {
- fn type_url() -> &'static str {
- concat!("type.googleapis.com/arrow.flight.protocol.sql.",
stringify!($name))
+ ($($name:tt,)*) => {
+ paste! {
+ $(
+ const [<$name:snake:upper _TYPE_URL>]: &'static str =
concat!("type.googleapis.com/arrow.flight.protocol.sql.", stringify!($name));
+ )*
+
+ as_item! {
+ pub enum Commands {
+ $($name($name),)*
}
+ }
- fn as_any(&self) -> Any {
- Any {
- type_url: <$name>::type_url().to_string(),
- value: self.encode_to_vec().into(),
+ impl Commands {
+ pub fn unpack(any: Any) -> Result<Commands, ArrowError> {
Review Comment:
Agreed – I've removed unpack completely, as `Command::try_from` or
`any.try_into()` is much better 👍🏻
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