Improve error handling around PointFieldDatatype

Author: grtlr

crates/utils/re_mcap/src/parsers/ros2msg/definitions/sensor_msgs.rs

@@ -110,12 +110,9 @@ pub struct Imu {
 }
 
 #[derive(Copy, Clone, Debug, Serialize, Deserialize)]
-#[serde(from = "u8", into = "u8")]
+#[serde(try_from = "u8", into = "u8")]
 #[repr(u8)]
 pub enum PointFieldDatatype {
-    /// Does not exist in original spec.
-    /// <https://docs.ros.org/en/noetic/api/sensor_msgs/html/msg/PointField.html>
-    Unknown = 0,
     Int8 = 1,
     UInt8 = 2,
     Int16 = 3,
@@ -126,9 +123,11 @@ pub enum PointFieldDatatype {
     Float64 = 8,
 }
 
-impl From<u8> for PointFieldDatatype {
-    fn from(value: u8) -> Self {
-        match value {
+impl TryFrom<u8> for PointFieldDatatype {
+    type Error = u8;
+
+    fn try_from(value: u8) -> Result<Self, Self::Error> {
+        Ok(match value {
             1 => Self::Int8,
             2 => Self::UInt8,
             3 => Self::Int16,
@@ -137,8 +136,8 @@ impl From<u8> for PointFieldDatatype {
             6 => Self::UInt32,
             7 => Self::Float32,
             8 => Self::Float64,
-            _ => Self::Unknown,
-        }
+            other => Err(other)?,
+        })
     }
 }
 

crates/utils/re_mcap/src/parsers/ros2msg/sensor_msgs/point_cloud_2.rs

@@ -90,7 +90,6 @@ impl PointCloud2MessageParser {
 
 fn builder_from_datatype(datatype: PointFieldDatatype) -> Box<dyn ArrayBuilder> {
     match datatype {
-        PointFieldDatatype::Unknown => unreachable!(),
         PointFieldDatatype::Int8 => Box::new(Int8Builder::new()),
         PointFieldDatatype::UInt8 => Box::new(UInt8Builder::new()),
         PointFieldDatatype::Int16 => Box::new(Int16Builder::new()),
@@ -105,7 +104,6 @@ fn builder_from_datatype(datatype: PointFieldDatatype) -> Box<dyn ArrayBuilder>
 fn access(data: &[u8], datatype: PointFieldDatatype, is_big_endian: bool) -> std::io::Result<f32> {
     let mut rdr = Cursor::new(data);
     match (is_big_endian, datatype) {
-        (_, PointFieldDatatype::Unknown) => Ok(0f32), // Not in the original spec.
         (_, PointFieldDatatype::UInt8) => rdr.read_u8().map(|x| x as f32),
         (_, PointFieldDatatype::Int8) => rdr.read_i8().map(|x| x as f32),
         (true, PointFieldDatatype::Int16) => rdr.read_i16::<BigEndian>().map(|x| x as f32),
@@ -126,9 +124,6 @@ fn access(data: &[u8], datatype: PointFieldDatatype, is_big_endian: bool) -> std
 impl From<PointFieldDatatype> for DataType {
     fn from(value: PointFieldDatatype) -> Self {
         match value {
-            // Not part of the MCAP spec
-            // // https://docs.ros.org/en/noetic/api/sensor_msgs/html/msg/PointField.html
-            PointFieldDatatype::Unknown => unreachable!(),
             PointFieldDatatype::Int8 => Self::Int8,
             PointFieldDatatype::UInt8 => Self::UInt8,
             PointFieldDatatype::Int16 => Self::Int16,
@@ -215,7 +210,6 @@ fn add_field_value(
 ) -> anyhow::Result<()> {
     let mut rdr = Cursor::new(data);
     match field.datatype {
-        PointFieldDatatype::Unknown => unreachable!(),
         PointFieldDatatype::Int8 => {
             let builder = builder
                 .as_any_mut()