Enable listing resources for cycle and vehicle

Also add python tests to confirm results

python/fastsim/tests/test_resources.py

@@ -6,10 +6,22 @@
 
 class TestListResources(unittest.TestCase):
     def test_list_resources_for_cycle(self):
-        "check if list_resources works and yields results for Cycle"
+        "check if list_resources works for RustCycle"
         c = cycle.Cycle.from_dict({
             "cycSecs": [0.0, 1.0],
             "cycMps": [0.0, 0.0]})
         rc = c.to_rust()
         resources = rc.list_resources()
         self.assertTrue(len(resources) > 0)
+
+    def test_list_resources_for_vehicles(self):
+        "check if list_resources works for RustVehicle"
+        # NOTE: at the time of writing this test,
+        #       there are no vehicle assets in resources.
+        #       Therefore, we expect to get an empty vector.
+        #       If resources are committed, this test should
+        #       fail and we should use the following assert:
+        #   self.assertTrue(len(resources) > 0)
+        rv = vehicle.Vehicle.from_vehdb(1).to_rust()
+        resources = rv.list_resources()
+        self.assertTrue(len(resources) == 0)

rust/fastsim-core/src/resources.rs

@@ -5,21 +5,21 @@ pub const RESOURCES_DIR: Dir = include_dir!("$CARGO_MANIFEST_DIR/resources");
 
 /// List the available resources in the resources directory
 /// - subdir: &str, a subdirectory to choose from the resources directory
-///   if it cannot be resolved, then the top level is used to list resources
-/// NOTE: if you want the top level, a good way to get that is to pass "".
+/// NOTE: if subdir cannot be resolved, returns an empty list
 /// RETURNS: a vector of strings for resources that can be loaded
 pub fn list_resources(subdir: &str) -> Vec<String> {
-    let resources_path = if let Some(rp) = RESOURCES_DIR.get_dir(subdir) {
-        rp
+    if subdir.is_empty() {
+        Vec::<String>::new()
+    } else if let Some(resources_path) = RESOURCES_DIR.get_dir(subdir) {
+        let mut file_names: Vec<String> = resources_path
+            .files()
+            .filter_map(|entry| entry.path().file_name()?.to_str().map(String::from))
+            .collect();
+        file_names.sort();
+        file_names
     } else {
-        &RESOURCES_DIR
-    };
-    let mut file_names: Vec<String> = resources_path
-        .files()
-        .filter_map(|entry| entry.path().file_name()?.to_str().map(String::from))
-        .collect();
-    file_names.sort();
-    file_names
+        Vec::<String>::new()
+    }
 }
 
 #[cfg(test)]
@@ -31,5 +31,11 @@ mod tests {
         let result = list_resources("cycles");
         assert!(result.len() == 3);
         assert!(result[0] == "HHDDTCruiseSmooth.csv");
+        // NOTE: at the time of writing this test, there is no
+        // vehicles subdirectory. The agreed-upon behavior in
+        // that case is that list_resources should return an
+        // empty vector of string.
+        let another_result = list_resources("vehicles");
+        assert!(another_result.len() == 0);
     }
 }

rust/fastsim-core/src/vehicle.rs

@@ -83,6 +83,12 @@ lazy_static! {
         self.clone()
     }
 
+    #[pyo3(name = "list_resources")]
+    /// list available vehicle resources
+    pub fn list_resources_py(&self) -> Vec<String> {
+        RustVehicle::list_resources()
+    }
+
     #[staticmethod]
     #[pyo3(name = "mock_vehicle")]
     fn mock_vehicle_py() -> Self {