Add optional defmt::Format support for generated types

- Derived for enum types
- Formats messages by printing individual field values
- Enabled in can-messages test generation.

Cargo.toml

@@ -24,6 +24,9 @@ heck = "0.4.0"
 typed-builder = "0.18.0"
 embedded-can = "0.4.1"
 
+[dev-dependencies]
+defmt = "0.3.8"
+
 [workspace]
 members = [
     ".",

src/lib.rs

@@ -60,6 +60,10 @@ pub struct Config<'a> {
     #[builder(default)]
     pub impl_debug: FeatureConfig<'a>,
 
+    /// Optional: `impl defmt::Format` for generated types. Default: `Never`.
+    #[builder(default)]
+    pub impl_defmt: FeatureConfig<'a>,
+
     /// Optional: `impl Arbitrary` for generated types. Default: `Never`.
     #[builder(default)]
     pub impl_arbitrary: FeatureConfig<'a>,
@@ -189,6 +193,7 @@ fn render_root_enum(mut w: impl Write, dbc: &DBC, config: &Config<'_>) -> Result
     writeln!(w, "/// All messages")?;
     writeln!(w, "#[derive(Clone)]")?;
     config.impl_debug.fmt_attr(&mut w, "derive(Debug)")?;
+    config.impl_defmt.fmt_attr(&mut w, "derive(defmt::Format)")?;
     config.impl_serde.fmt_attr(&mut w, "derive(Serialize)")?;
     config.impl_serde.fmt_attr(&mut w, "derive(Deserialize)")?;
     writeln!(w, "pub enum Messages {{")?;
@@ -430,6 +435,8 @@ fn render_message(mut w: impl Write, config: &Config<'_>, msg: &Message, dbc: &D
 
     render_debug_impl(&mut w, config, msg)?;
 
+    render_defmt_impl(&mut w, config, msg)?;
+
     render_arbitrary(&mut w, config, msg)?;
 
     let enums_for_this_message = dbc.value_descriptions().iter().filter_map(|x| {
@@ -984,6 +991,7 @@ fn write_enum(
     writeln!(w, "/// Defined values for {}", signal.name())?;
     writeln!(w, "#[derive(Clone, Copy, PartialEq)]")?;
     config.impl_debug.fmt_attr(&mut w, "derive(Debug)")?;
+    config.impl_defmt.fmt_attr(&mut w, "derive(defmt::Format)")?;
     config.impl_serde.fmt_attr(&mut w, "derive(Serialize)")?;
     config.impl_serde.fmt_attr(&mut w, "derive(Deserialize)")?;
     writeln!(w, "pub enum {} {{", type_name)?;
@@ -1385,6 +1393,54 @@ fn render_debug_impl(mut w: impl Write, config: &Config<'_>, msg: &Message) -> R
     Ok(())
 }
 
+fn render_defmt_impl(mut w: impl Write, config: &Config<'_>, msg: &Message) -> Result<()> {
+    match &config.impl_defmt {
+        FeatureConfig::Always => {}
+        FeatureConfig::Gated(gate) => writeln!(w, r##"#[cfg(feature = {gate:?})]"##)?,
+        FeatureConfig::Never => return Ok(()),
+    }
+
+    let typ = type_name(msg.message_name());
+    writeln!(w, r##"impl defmt::Format for {} {{"##, typ)?;
+    {
+        let mut w = PadAdapter::wrap(&mut w);
+        writeln!(
+            w,
+            "fn format(&self, f: defmt::Formatter) {{"
+        )?;
+        {
+            let mut w = PadAdapter::wrap(&mut w);
+            writeln!(w, r#"defmt::write!(f,"#)?;
+            {
+                let mut w = PadAdapter::wrap(&mut w);
+                write!(w, r#""{} {{{{"#, typ)?;
+                {
+                    for signal in msg.signals() {
+                        if *signal.multiplexer_indicator() == MultiplexIndicator::Plain {
+                            write!(w,
+                                   r#" {}={{:?}}"#,
+                                   signal.name(),
+                            )?;
+                        }
+                    }
+                }
+                writeln!(w, r#" }}}}","#)?;
+
+                for signal in msg.signals() {
+                    if *signal.multiplexer_indicator() == MultiplexIndicator::Plain {
+                        writeln!(w, "self.{}(),", field_name(signal.name()))?;
+                    }
+                }
+                writeln!(w, r#");"#)?;
+            }
+            writeln!(w, "}}")?;
+        }
+    }
+    writeln!(w, "}}")?;
+    writeln!(w)?;
+    Ok(())
+}
+
 fn render_multiplexor_enums(
     mut w: impl Write,
     config: &Config<'_>,
@@ -1416,6 +1472,7 @@ fn render_multiplexor_enums(
     )?;
 
     config.impl_debug.fmt_attr(&mut w, "derive(Debug)")?;
+    config.impl_defmt.fmt_attr(&mut w, "derive(defmt::Format)")?;
     config.impl_serde.fmt_attr(&mut w, "derive(Serialize)")?;
     config.impl_serde.fmt_attr(&mut w, "derive(Deserialize)")?;
     writeln!(
@@ -1443,6 +1500,7 @@ fn render_multiplexor_enums(
         let struct_name = multiplexed_enum_variant_name(msg, multiplexor_signal, **switch_index)?;
 
         config.impl_debug.fmt_attr(&mut w, "derive(Debug)")?;
+        config.impl_defmt.fmt_attr(&mut w, "derive(defmt::Format)")?;
         config.impl_serde.fmt_attr(&mut w, "derive(Serialize)")?;
         config.impl_serde.fmt_attr(&mut w, "derive(Deserialize)")?;
         writeln!(w, r##"#[derive(Default)]"##)?;

testing/can-messages/Cargo.toml

@@ -8,6 +8,7 @@ edition = "2021"
 bitvec = { version = "1.0", default-features = false }
 arbitrary = { version = "1.0", optional = true }
 embedded-can = "0.4.1"
+defmt = "0.3.8"
 
 [build-dependencies]
 anyhow = "1.0"

testing/can-messages/build.rs

@@ -19,6 +19,7 @@ fn main() -> Result<()> {
         .dbc_content(&dbc_file)
         .debug_prints(true)
         .impl_debug(FeatureConfig::Always)
+        .impl_defmt(FeatureConfig::Always)
         .impl_error(FeatureConfig::Gated("std"))
         .impl_arbitrary(FeatureConfig::Gated("arb"))
         .check_ranges(FeatureConfig::Always)