do not use () as Err, clean up error handling

src/command_code.rs

@@ -33,8 +33,12 @@ impl From<CommandCode> for u16 {
     }
 }
 
+#[derive(Debug, thiserror::Error, Eq, PartialEq)]
+#[error("The command code {0} is not known.")]
+pub struct InvalidCommandCodeError(pub u16);
+
 impl TryFrom<u16> for CommandCode {
-    type Error = ();
+    type Error = InvalidCommandCodeError;
 
     /// Returns the enum value for the specified `u16` or `Error` if the code is unknown.
     fn try_from(value: u16) -> Result<Self, Self::Error> {
@@ -97,7 +101,7 @@ impl TryFrom<u16> for CommandCode {
             value if value == CommandCode::Utf8Data as u16 => {
                 Ok(CommandCode::Utf8Data)
             }
-            _ => Err(()),
+            _ => Err(InvalidCommandCodeError(value)),
         }
     }
 }

src/commands/bitmap.rs

@@ -1,5 +1,5 @@
 use crate::{
-    command_code::CommandCode,
+    command_code::{CommandCode, InvalidCommandCodeError},
     commands::errors::{TryFromPacketError, TryIntoPacketError},
     compression::into_compressed,
     compression::into_decompressed,
@@ -83,10 +83,7 @@ impl TryFrom<Packet> for BitmapCommand {
     type Error = TryFromPacketError;
 
     fn try_from(packet: Packet) -> Result<Self, Self::Error> {
-        let code = CommandCode::try_from(packet.header.command_code).map_err(
+        let code = CommandCode::try_from(packet.header.command_code)?;
-            |()| TryFromPacketError::InvalidCommand(packet.header.command_code),
-        )?;
-
         match code {
             CommandCode::BitmapLinearWinUncompressed => {
                 Self::packet_into_bitmap_win(
@@ -111,9 +108,9 @@ impl TryFrom<Packet> for BitmapCommand {
                 Self::packet_into_bitmap_win(packet, CompressionCode::Zstd)
             }
 
-            _ => Err(TryFromPacketError::InvalidCommand(
+            _ => {
-                packet.header.command_code,
+                Err(InvalidCommandCodeError(packet.header.command_code).into())
-            )),
+            }
         }
     }
 }
@@ -182,9 +179,7 @@ mod tests {
                     ..Default::default()
                 }
             }),
-            Err(TryFromPacketError::InvalidCommand(
+            Err(InvalidCommandCodeError(CommandCode::Brightness.into()).into())
-                CommandCode::Brightness.into()
-            ))
         );
     }
 

src/commands/bitvec.rs

@@ -1,7 +1,8 @@
 use crate::{
-    command_code::CommandCode, commands::errors::TryFromPacketError,
+    command_code::CommandCode, command_code::InvalidCommandCodeError,
-    compression::into_compressed, compression::into_decompressed, BitVec,
+    commands::errors::TryFromPacketError, compression::into_compressed,
-    CompressionCode, Header, Offset, Packet, TryIntoPacketError, TypedCommand,
+    compression::into_decompressed, BitVec, CompressionCode, Header, Offset,
+    Packet, TryIntoPacketError, TypedCommand,
 };
 
 /// Binary operations for use with the [`BitVecCommand`] command.
@@ -86,29 +87,21 @@ impl TryFrom<Packet> for BitVecCommand {
                 },
             payload,
         } = packet;
-        let command_code = CommandCode::try_from(command_code)
+        let command_code = CommandCode::try_from(command_code)?;
-            .map_err(|()| TryFromPacketError::InvalidCommand(command_code))?;
         let operation = match command_code {
             CommandCode::BitmapLinear => BinaryOperation::Overwrite,
             CommandCode::BitmapLinearAnd => BinaryOperation::And,
             CommandCode::BitmapLinearOr => BinaryOperation::Or,
             CommandCode::BitmapLinearXor => BinaryOperation::Xor,
             _ => {
-                return Err(TryFromPacketError::InvalidCommand(
+                return Err(InvalidCommandCodeError(command_code.into()).into());
-                    command_code.into(),
-                ))
             }
         };
 
         if reserved != 0 {
             return Err(TryFromPacketError::ExtraneousHeaderValues);
         }
-        let compression = match CompressionCode::try_from(sub) {
+        let compression = CompressionCode::try_from(sub)?;
-            Err(()) => {
-                return Err(TryFromPacketError::InvalidCompressionCode(sub));
-            }
-            Ok(value) => value,
-        };
         let payload = match into_decompressed(compression, payload) {
             None => return Err(TryFromPacketError::DecompressionFailed),
             Some(value) => value,
@@ -138,6 +131,7 @@ impl From<BitVecCommand> for TypedCommand {
 mod tests {
     use super::*;
     use crate::commands::tests::{round_trip, TestImplementsCommand};
+    use crate::compression_code::InvalidCompressionCodeError;
     use crate::{commands, Bitmap, BitmapCommand, Origin};
 
     impl TestImplementsCommand for BitVecCommand {}
@@ -152,9 +146,7 @@ mod tests {
                     ..Default::default()
                 }
             }),
-            Err(TryFromPacketError::InvalidCommand(
+            Err(InvalidCommandCodeError(CommandCode::Brightness.into()).into())
-                CommandCode::Brightness.into()
-            ))
         );
     }
 
@@ -285,7 +277,7 @@ mod tests {
         };
         assert_eq!(
             TypedCommand::try_from(p),
-            Err(TryFromPacketError::InvalidCompressionCode(42))
+            Err(InvalidCompressionCodeError(42).into())
         );
     }
 

src/commands/clear.rs

@@ -1,6 +1,7 @@
 use crate::{
-    command_code::CommandCode, commands::check_command_code_only,
+    command_code::CommandCode,
-    commands::errors::TryFromPacketError, Packet, TypedCommand,
+    commands::{check_command_code_only, errors::TryFromPacketError},
+    Packet, TypedCommand,
 };
 use std::fmt::Debug;
 
@@ -43,6 +44,7 @@ impl From<ClearCommand> for TypedCommand {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::command_code::InvalidCommandCodeError;
     use crate::commands::tests::TestImplementsCommand;
     use crate::Header;
 
@@ -85,9 +87,7 @@ mod tests {
             payload: vec![],
         };
         assert_eq!(
-            Err(TryFromPacketError::InvalidCommand(
+            Err(InvalidCommandCodeError(CommandCode::HardReset.into()).into()),
-                CommandCode::HardReset.into()
-            )),
             ClearCommand::try_from(p)
         );
     }

src/commands/errors.rs

@@ -1,12 +1,15 @@
-use crate::LoadBitmapError;
+use crate::{
+    command_code::InvalidCommandCodeError,
+    compression_code::InvalidCompressionCodeError, LoadBitmapError,
+};
 use std::num::TryFromIntError;
 
 /// Err values for [`crate::TypedCommand::try_from`].
 #[derive(Debug, PartialEq, thiserror::Error)]
 pub enum TryFromPacketError {
     /// the contained command code does not correspond to a known command
-    #[error("The command code {0:?} does not correspond to a known command")]
+    #[error(transparent)]
-    InvalidCommand(u16),
+    InvalidCommand(#[from] InvalidCommandCodeError),
     /// the expected payload size was n, but size m was found
     #[error("the expected payload size was {0}, but size {1} was found")]
     UnexpectedPayloadSize(usize, usize),
@@ -16,8 +19,8 @@ pub enum TryFromPacketError {
     #[error("Header fields not needed for the command have been used")]
     ExtraneousHeaderValues,
     /// The contained compression code is not known. This could be of disabled features.
-    #[error("The compression code {0:?} does not correspond to a known compression algorithm.")]
+    #[error(transparent)]
-    InvalidCompressionCode(u16),
+    InvalidCompression(#[from] InvalidCompressionCodeError),
     /// Decompression of the payload failed. This can be caused by corrupted packets.
     #[error("The decompression of the payload failed")]
     DecompressionFailed,

src/commands/mod.rs

@@ -11,7 +11,7 @@ mod fade_out;
 mod hard_reset;
 mod typed;
 
-use crate::command_code::CommandCode;
+use crate::command_code::{CommandCode, InvalidCommandCodeError};
 use crate::{Header, Packet};
 use std::fmt::Debug;
 
@@ -99,9 +99,7 @@ fn check_command_code_only(
         payload,
     } = packet;
     if packet.header.command_code != u16::from(code) {
-        Some(TryFromPacketError::InvalidCommand(
+        Some(InvalidCommandCodeError(packet.header.command_code).into())
-            packet.header.command_code,
-        ))
     } else if !payload.is_empty() {
         Some(TryFromPacketError::UnexpectedPayloadSize(0, payload.len()))
     } else if a != 0 || b != 0 || c != 0 || d != 0 {
@@ -114,11 +112,11 @@ fn check_command_code_only(
 fn check_command_code(
     actual: u16,
     expected: CommandCode,
-) -> Result<(), TryFromPacketError> {
+) -> Result<(), InvalidCommandCodeError> {
     if actual == u16::from(expected) {
         Ok(())
     } else {
-        Err(TryFromPacketError::InvalidCommand(actual))
+        Err(InvalidCommandCodeError(actual))
     }
 }
 
@@ -126,6 +124,10 @@ fn check_command_code(
 mod tests {
     use crate::*;
 
+    #[allow(
+        unused,
+        reason = "false positive, used in submodules that check if structs impl Command"
+    )]
     pub(crate) trait TestImplementsCommand: Command {}
 
     pub(crate) fn round_trip(original: TypedCommand) {

src/commands/typed.rs

@@ -2,7 +2,7 @@ use crate::{
     command_code::CommandCode, commands::errors::TryFromPacketError,
     BitVecCommand, BitmapCommand, BrightnessCommand, BrightnessGridCommand,
     CharGridCommand, ClearCommand, Cp437GridCommand, FadeOutCommand,
-    HardResetCommand, Header, Packet, TryIntoPacketError,
+    HardResetCommand, Packet, TryIntoPacketError,
 };
 
 /// This enum contains all commands provided by the library.
@@ -31,18 +31,7 @@ impl TryFrom<Packet> for TypedCommand {
 
     /// Try to interpret the [Packet] as one containing a [Command]
     fn try_from(packet: Packet) -> Result<Self, Self::Error> {
-        let Packet {
+        Ok(match CommandCode::try_from(packet.header.command_code)? {
-            header: Header { command_code, .. },
-            ..
-        } = packet;
-        let command_code = match CommandCode::try_from(command_code) {
-            Err(()) => {
-                return Err(TryFromPacketError::InvalidCommand(command_code));
-            }
-            Ok(value) => value,
-        };
-
-        Ok(match command_code {
             CommandCode::Clear => {
                 TypedCommand::Clear(crate::ClearCommand::try_from(packet)?)
             }
@@ -119,9 +108,10 @@ impl TryFrom<TypedCommand> for Packet {
 
 #[cfg(test)]
 mod tests {
-    use crate::commands::errors::TryFromPacketError;
+    use crate::{
-    use crate::commands::tests::TestImplementsCommand;
+        command_code::InvalidCommandCodeError,
-    use crate::{Header, Packet, TypedCommand};
+        commands::tests::TestImplementsCommand, Header, Packet, TypedCommand,
+    };
 
     impl TestImplementsCommand for TypedCommand {}
 
@@ -138,9 +128,6 @@ mod tests {
             payload: vec![],
         };
         let result = TypedCommand::try_from(p);
-        assert!(matches!(
+        assert_eq!(result, Err(InvalidCommandCodeError(0xFF).into()));
-            result,
-            Err(TryFromPacketError::InvalidCommand(0xFF))
-        ));
     }
 }

src/compression_code.rs

@@ -54,6 +54,10 @@ impl CompressionCode {
     ];
 }
 
+#[derive(Debug, thiserror::Error, Eq, PartialEq)]
+#[error("The compression code {0} is not known.")]
+pub struct InvalidCompressionCodeError(pub u16);
+
 impl From<CompressionCode> for u16 {
     fn from(value: CompressionCode) -> Self {
         value as u16
@@ -61,7 +65,7 @@ impl From<CompressionCode> for u16 {
 }
 
 impl TryFrom<u16> for CompressionCode {
-    type Error = ();
+    type Error = InvalidCompressionCodeError;
 
     fn try_from(value: u16) -> Result<Self, Self::Error> {
         match value {
@@ -84,7 +88,7 @@ impl TryFrom<u16> for CompressionCode {
             value if value == CompressionCode::Zstd as u16 => {
                 Ok(CompressionCode::Zstd)
             }
-            _ => Err(()),
+            _ => Err(InvalidCompressionCodeError(value)),
         }
     }
 }

src/packet.rs

@@ -92,15 +92,19 @@ impl From<Packet> for Vec<u8> {
     }
 }
 
+#[derive(Debug, thiserror::Error, Eq, PartialEq)]
+#[error("The provided slice is smaller than the header size, so it cannot be read as a packet.")]
+pub struct SliceSmallerThanHeader;
+
 impl TryFrom<&[u8]> for Packet {
-    type Error = ();
+    type Error = SliceSmallerThanHeader;
 
     /// Tries to interpret the bytes as a [Packet].
     ///
     /// returns: `Error` if slice is not long enough to be a [Packet]
     fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
         if value.len() < size_of::<Header>() {
-            return Err(());
+            return Err(SliceSmallerThanHeader);
         }
 
         let header = {
@@ -124,7 +128,7 @@ impl TryFrom<&[u8]> for Packet {
 }
 
 impl TryFrom<Vec<u8>> for Packet {
-    type Error = ();
+    type Error = SliceSmallerThanHeader;
 
     fn try_from(value: Vec<u8>) -> Result<Self, Self::Error> {
         Self::try_from(value.as_slice())
@@ -203,6 +207,9 @@ mod tests {
     #[test]
     fn too_small() {
         let data = vec![0u8; 4];
-        assert_eq!(Packet::try_from(data.as_slice()), Err(()));
+        assert_eq!(
+            Packet::try_from(data.as_slice()),
+            Err(SliceSmallerThanHeader)
+        );
     }
 }