Update embedded-io-adapters to swap Ok(0) for Err when required

Author: adamgreig

embedded-io-adapters/CHANGELOG.md

@@ -8,7 +8,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Unreleased
 
 - Add support for adapting `BufRead` from `futures` and `tokio`.
+- Return an error when a wrapped `std`/`futures`/`tokio` `write()` call returns
+  `Ok(0)` to comply with `embedded_io::Write` requirements.
 
 ## 0.5.0 - 2023-08-06
 
-- First release
+- First release

embedded-io-adapters/src/futures_03.rs

@@ -57,7 +57,11 @@ impl<T: futures::io::AsyncBufRead + Unpin + ?Sized> embedded_io_async::BufRead f
 
 impl<T: futures::io::AsyncWrite + Unpin + ?Sized> embedded_io_async::Write for FromFutures<T> {
     async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
-        poll_fn(|cx| Pin::new(&mut self.inner).poll_write(cx, buf)).await
+        match poll_fn(|cx| Pin::new(&mut self.inner).poll_write(cx, buf)).await {
+            Ok(0) if !buf.is_empty() => Err(std::io::ErrorKind::WriteZero.into()),
+            Ok(n) => Ok(n),
+            Err(e) => Err(e),
+        }
     }
 
     async fn flush(&mut self) -> Result<(), Self::Error> {

embedded-io-adapters/src/std.rs

@@ -1,5 +1,7 @@
 //! Adapters to/from `std::io` traits.
 
+use embedded_io::Error;
+
 /// Adapter from `std::io` traits.
 #[derive(Clone)]
 pub struct FromStd<T: ?Sized> {
@@ -52,7 +54,11 @@ impl<T: std::io::BufRead + ?Sized> embedded_io::BufRead for FromStd<T> {
 
 impl<T: std::io::Write + ?Sized> embedded_io::Write for FromStd<T> {
     fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
-        self.inner.write(buf)
+        match self.inner.write(buf) {
+            Ok(0) if !buf.is_empty() => Err(std::io::ErrorKind::WriteZero.into()),
+            Ok(n) => Ok(n),
+            Err(e) => Err(e),
+        }
     }
     fn flush(&mut self) -> Result<(), Self::Error> {
         self.inner.flush()
@@ -103,7 +109,11 @@ impl<T: embedded_io::Read + ?Sized> std::io::Read for ToStd<T> {
 
 impl<T: embedded_io::Write + ?Sized> std::io::Write for ToStd<T> {
     fn write(&mut self, buf: &[u8]) -> Result<usize, std::io::Error> {
-        self.inner.write(buf).map_err(to_std_error)
+        match self.inner.write(buf) {
+            Ok(n) => Ok(n),
+            Err(e) if e.kind() == embedded_io::ErrorKind::WriteZero => Ok(0),
+            Err(e) => Err(to_std_error(e)),
+        }
     }
     fn flush(&mut self) -> Result<(), std::io::Error> {
         self.inner.flush().map_err(to_std_error)

embedded-io-adapters/src/tokio_1.rs

@@ -68,7 +68,11 @@ impl<T: tokio::io::AsyncBufRead + Unpin + ?Sized> embedded_io_async::BufRead for
 
 impl<T: tokio::io::AsyncWrite + Unpin + ?Sized> embedded_io_async::Write for FromTokio<T> {
     async fn write(&mut self, buf: &[u8]) -> Result<usize, Self::Error> {
-        poll_fn(|cx| Pin::new(&mut self.inner).poll_write(cx, buf)).await
+        match poll_fn(|cx| Pin::new(&mut self.inner).poll_write(cx, buf)).await {
+            Ok(0) if !buf.is_empty() => Err(std::io::ErrorKind::WriteZero.into()),
+            Ok(n) => Ok(n),
+            Err(e) => Err(e),
+        }
     }
 
     async fn flush(&mut self) -> Result<(), Self::Error> {