feat: adds a drop last step trace event

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "runtime_tracing"
-version = "0.5.12-experimental-1"
+version = "0.5.12-experimental-2"
 edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

src/lib.rs

@@ -24,7 +24,14 @@ mod tests {
  // -> function_id 1 after top level;
  let function_id = tracer.ensure_function_id("function", &path, function_line);
  assert!(function_id == FunctionId(1));
-
+
+ let before_temp_step = tracer.events.len();
+ tracer.register_step(path, function_line);
+ tracer.drop_last_step();
+ // drop last step: drops steps[-1]/variables[-]
+ assert_eq!(before_temp_step + 2, tracer.events.len());
+ assert!(matches!(tracer.events.last().unwrap(), TraceLowLevelEvent::DropLastStep));
+
  let args = vec![tracer.arg("a", NONE_VALUE), tracer.arg("b", NONE_VALUE)];
  tracer.register_call(function_id, args);
  // => arg-related variable/value events; auto call-step event; potentially variables; call event
@@ -63,7 +70,7 @@ mod tests {
 
  tracer.register_return(NONE_VALUE);
 
- assert_eq!(tracer.events.len(), 21);
+ assert_eq!(tracer.events.len(), 23);
  // visible with
  // cargo tets -- --nocapture
  // println!("{:#?}", tracer.events);

src/tracer.rs

@@ -179,6 +179,10 @@ impl Tracer {
  self.events.push(TraceLowLevelEvent::Value(FullValueRecord { variable_id, value }));
  }
 
+ pub fn drop_last_step(&mut self) {
+ self.events.push(TraceLowLevelEvent::DropLastStep);
+ }
+
  pub fn store_trace_metadata(&self, path: &Path) -> Result<(), Box<dyn Error>> {
  let trace_metadata = TraceMetadata {
  program: self.program.clone(),

src/types.rs

@@ -17,6 +17,7 @@ pub enum TraceLowLevelEvent {
  Call(CallRecord),
  Return(ReturnRecord),
  Event(RecordEvent),
+ DropLastStep,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]