Separate functions for allowing/disallowing empty csv files

src/input.rs

@@ -1,7 +1,7 @@
 //! Common routines for handling input data.
 use crate::agent::AssetPool;
 use crate::model::{Model, ModelFile};
-use anyhow::{ensure, Context, Result};
+use anyhow::{bail, ensure, Context, Result};
 use float_cmp::approx_eq;
 use indexmap::IndexMap;
 use itertools::Itertools;
@@ -26,19 +26,41 @@ pub use time_slice::read_time_slice_info;
 
 /// Read a series of type `T`s from a CSV file.
 ///
+/// Will raise an error if the file is empty.
+///
 /// # Arguments
 ///
 /// * `file_path` - Path to the CSV file
 pub fn read_csv<'a, T: DeserializeOwned + 'a>(
     file_path: &'a Path,
 ) -> Result<impl Iterator<Item = T> + 'a> {
+    let vec = _read_csv_internal(file_path)?;
+    if vec.is_empty() {
+        bail!("CSV file {} cannot be empty", file_path.display());
+    }
+    Ok(vec.into_iter())
+}
+
+/// Read a series of type `T`s from a CSV file.
+///
+/// # Arguments
+///
+/// * `file_path` - Path to the CSV file
+pub fn read_csv_optional<'a, T: DeserializeOwned + 'a>(
+    file_path: &'a Path,
+) -> Result<impl Iterator<Item = T> + 'a> {
+    let vec = _read_csv_internal(file_path)?;
+    Ok(vec.into_iter())
+}
+
+fn _read_csv_internal<'a, T: DeserializeOwned + 'a>(file_path: &'a Path) -> Result<Vec<T>> {
     let vec = csv::Reader::from_path(file_path)
         .with_context(|| input_err_msg(file_path))?
         .into_deserialize()
         .process_results(|iter| iter.collect_vec())
         .with_context(|| input_err_msg(file_path))?;
 
-    Ok(vec.into_iter())
+    Ok(vec)
 }
 
 /// Parse a TOML file at the specified path.
@@ -285,6 +307,14 @@ mod tests {
                 }
             ]
         );
+
+        // File with no data (only column headers)
+        let file_path = create_csv_file(dir.path(), "id,value\n");
+        assert!(read_csv::<Record>(&file_path).is_err());
+        assert!(read_csv_optional::<Record>(&file_path)
+            .unwrap()
+            .next()
+            .is_none());
     }
 
     #[test]

src/input/agent/search_space.rs

@@ -81,7 +81,7 @@ pub fn read_agent_search_space(
     milestone_years: &[u32],
 ) -> Result<HashMap<Rc<str>, Vec<AgentSearchSpace>>> {
     let file_path = model_dir.join(AGENT_SEARCH_SPACE_FILE_NAME);
-    let iter = read_csv::<AgentSearchSpaceRaw>(&file_path)?;
+    let iter = read_csv_optional::<AgentSearchSpaceRaw>(&file_path)?;
     read_agent_search_space_from_iter(iter, agents, process_ids, commodities, milestone_years)
         .with_context(|| input_err_msg(&file_path))
 }