impl Drop for async File & Volume with embassy_futures::block_on

Author: Be-ing

Cargo.toml

@@ -17,6 +17,7 @@ rust-version = "1.76"
 bisync = "0.3.0"
 byteorder = {version = "1", default-features = false}
 defmt = {version = "0.3", optional = true}
+embassy-futures = {version = "0.1.1", optional = true}
 embedded-hal = "1.0.0"
 embedded-hal-async = "1.0.0"
 embedded-io = "0.6.1"
@@ -33,6 +34,7 @@ hex-literal = "0.4.1"
 sha2 = "0.10"
 
 [features]
-default = ["log"]
+default = ["log", "async-drop"]
 defmt-log = ["dep:defmt"]
 log = ["dep:log"]
+async-drop = ["dep:embassy-futures"]

src/inner/filesystem/files.rs

@@ -1,4 +1,4 @@
-use super::super::super::{bisync, only_sync};
+use super::super::super::{bisync, only_sync, only_async};
 use super::super::super::{ErrorType, Read, Seek, SeekFrom, Write};
 use super::super::{
     filesystem::{ClusterId, DirEntry, Handle},
@@ -49,8 +49,11 @@ impl RawFile {
 /// error that may occur will be ignored. To handle potential errors, use
 /// the [`File::close`] method.
 ///
-/// For async Files, async drop does not exist in Rust, so you *must* call
-/// [`File::close`] when you are done with a File.
+/// For async Files, the implementation of [`Drop`] blocks with [`embassy_futures::block_on`]
+/// because there is no way to `.await` inside [`Drop::drop`]. If you would prefer
+/// to call [`File::close`] manually instead and rely on the async executor you are already
+/// using, you can do that by disabling the `async-drop` Cargo feature, which is enabled by
+/// default.
 pub struct File<'a, D, T, const MAX_DIRS: usize, const MAX_FILES: usize, const MAX_VOLUMES: usize>
 where
     D: BlockDevice,
@@ -150,7 +153,6 @@ where
     }
 }
 
-// async drop does not yet exist :(
 #[only_sync]
 impl<'a, D, T, const MAX_DIRS: usize, const MAX_FILES: usize, const MAX_VOLUMES: usize> Drop
     for File<'a, D, T, MAX_DIRS, MAX_FILES, MAX_VOLUMES>
@@ -163,6 +165,19 @@ where
     }
 }
 
+#[cfg(feature = "async-drop")]
+#[only_async]
+impl<'a, D, T, const MAX_DIRS: usize, const MAX_FILES: usize, const MAX_VOLUMES: usize> Drop
+    for File<'a, D, T, MAX_DIRS, MAX_FILES, MAX_VOLUMES>
+where
+    D: BlockDevice,
+    T: TimeSource,
+{
+    fn drop(&mut self) {
+        _ = embassy_futures::block_on(self.volume_mgr.close_file(self.raw_file));
+    }
+}
+
 impl<'a, D, T, const MAX_DIRS: usize, const MAX_FILES: usize, const MAX_VOLUMES: usize>
     core::fmt::Debug for File<'a, D, T, MAX_DIRS, MAX_FILES, MAX_VOLUMES>
 where

src/inner/mod.rs

@@ -19,7 +19,7 @@ use core::fmt::Debug;
 use embedded_io::ErrorKind;
 use filesystem::Handle;
 
-use super::{bisync, only_sync};
+use super::{bisync, only_sync, only_async};
 
 #[doc(inline)]
 pub use blockdevice::{Block, BlockCache, BlockCount, BlockDevice, BlockIdx};
@@ -210,8 +210,11 @@ impl RawVolume {
 /// any error that may occur will be ignored. To handle potential errors, use
 /// the [`Volume::close`] method.
 ///
-/// For async Volumes, async drop does not exist in Rust, so you *must* call
-/// [`Volume::close`] when you are done with a Volume.
+/// For async Volumes, the implementation of [`Drop`] blocks with [`embassy_futures::block_on`]
+/// because there is no way to `.await` inside [`Drop::drop`]. If you would prefer
+/// to call [`File::close`] manually instead and rely on the async executor you are already
+/// using, you can do that by disabling the `async-drop` Cargo feature, which is enabled by
+/// default.
 pub struct Volume<'a, D, T, const MAX_DIRS: usize, const MAX_FILES: usize, const MAX_VOLUMES: usize>
 where
     D: BlockDevice,
@@ -268,7 +271,6 @@ where
     }
 }
 
-// async drop does not yet exist :(
 #[only_sync]
 impl<'a, D, T, const MAX_DIRS: usize, const MAX_FILES: usize, const MAX_VOLUMES: usize> Drop
     for Volume<'a, D, T, MAX_DIRS, MAX_FILES, MAX_VOLUMES>
@@ -281,6 +283,19 @@ where
     }
 }
 
+#[cfg(feature = "async-drop")]
+#[only_async]
+impl<'a, D, T, const MAX_DIRS: usize, const MAX_FILES: usize, const MAX_VOLUMES: usize> Drop
+    for Volume<'a, D, T, MAX_DIRS, MAX_FILES, MAX_VOLUMES>
+where
+    D: BlockDevice,
+    T: TimeSource,
+{
+    fn drop(&mut self) {
+        _ = embassy_futures::block_on(self.volume_mgr.close_volume(self.raw_volume));
+    }
+}
+
 impl<'a, D, T, const MAX_DIRS: usize, const MAX_FILES: usize, const MAX_VOLUMES: usize>
     core::fmt::Debug for Volume<'a, D, T, MAX_DIRS, MAX_FILES, MAX_VOLUMES>
 where

src/lib.rs

@@ -70,6 +70,10 @@
 //!
 //! ## Features
 //!
+//! * `async-drop`: Enabled by default. Implements [`Drop`] for [`asynchronous::File`]
+//!    and [`asynchronous::Volume`] using [`embassy_futures::block_on`]. Disable if
+//!    you would prefer to call [`asynchronous::File::close`] and [`asynchronous::Volume::close`]
+//!    manually using the async executor you are already using.
 //! * `log`: Enabled by default. Generates log messages using the `log` crate.
 //! * `defmt-log`: By turning off the default features and enabling the
 //!   `defmt-log` feature you can configure this crate to log messages over defmt