Fix close method on child writer not closing

Fixes a bug where `child.stdin:close()` on a child process created by
`process.create()` did not actually close the `stdin`, this caused
processes which read from stdin until EOF to wait indefinitely.

On Unix, calling `close` on `async-process::ChildStdin` does not
actually close the underyling writer. This is due to it using
`async_io::Async` under the hood on Unix, whose `close` implementation
just flushes the underlying writer.

This has been fixed dropping the `ChildStdin` on close, which will close
the underlying writer. An existing test has been updated to catch this
bug.

Author: lukadev-0

crates/lune-std-process/src/create/child_writer.rs

@@ -10,36 +10,33 @@ use mlua::prelude::*;
 // Inner (plumbing) implementation
 
 #[derive(Debug)]
-enum ChildWriterInner {
-    None,
-    Stdin(AsyncChildStdin),
-}
+struct ChildWriterInner(Option<AsyncChildStdin>);
 
 impl ChildWriterInner {
     async fn write(&mut self, data: Vec<u8>) -> Result<(), std::io::Error> {
-        match self {
-            ChildWriterInner::None => Ok(()),
-            ChildWriterInner::Stdin(stdin) => stdin.write_all(&data).await,
+        if let Some(stdin) = self.0.as_mut() {
+            stdin.write_all(&data).await?;
         }
+        Ok(())
     }
 
     async fn close(&mut self) -> Result<(), std::io::Error> {
-        match self {
-            ChildWriterInner::None => Ok(()),
-            ChildWriterInner::Stdin(stdin) => stdin.close().await,
+        if let Some(mut stdin) = self.0.take() {
+            stdin.flush().await?;
         }
+        Ok(())
     }
 }
 
 impl From<AsyncChildStdin> for ChildWriterInner {
     fn from(stdin: AsyncChildStdin) -> Self {
-        ChildWriterInner::Stdin(stdin)
+        ChildWriterInner(Some(stdin))
     }
 }
 
 impl From<Option<AsyncChildStdin>> for ChildWriterInner {
     fn from(stdin: Option<AsyncChildStdin>) -> Self {
-        stdin.map_or(Self::None, Into::into)
+        ChildWriterInner(stdin)
     }
 }
 

tests/process/create/stream.luau

@@ -9,6 +9,9 @@ catChild.stdin:write(expected)
 catChild.stdin:close()
 local catOutput = catChild.stdout:read(#expected)
 
+-- Make sure the child exits
+catChild:status()
+
 assert(
 	expected == catOutput,
 	"Failed to write to stdin or read from stdout of child process!"