return float parsing error context in csv

milli/src/documents/builder.rs

@@ -115,14 +115,17 @@ impl<W: io::Write + io::Seek> DocumentBatchBuilder<W> {
             .map(|(k, t)| (this.index.insert(&k), t))
             .collect::<BTreeMap<_, _>>();
 
-        let records = records.into_records();
-
-        for record in records {
+        for (i, record) in records.into_records().enumerate() {
             let record = record?;
             let mut writer = obkv::KvWriter::new(Cursor::new(&mut this.obkv_buffer));
             for (value, (fid, ty)) in record.into_iter().zip(headers.iter()) {
                 let value = match ty {
-                    AllowedType::Number => value.parse::<f64>().map(Value::from)?,
+                    AllowedType::Number => value.parse::<f64>().map(Value::from).map_err(|error| Error::ParseFloat {
+                        error,
+                        // +1 for the header offset.
+                        line: i + 1,
+                        value: value.to_string(),
+                    })?,
                     AllowedType::String => Value::String(value.to_string()),
                 };
 

milli/src/documents/mod.rs

@@ -83,7 +83,11 @@ impl<W: io::Write> io::Write for ByteCounter<W> {
 
 #[derive(Debug)]
 pub enum Error {
-    ParseFloat(std::num::ParseFloatError),
+    ParseFloat {
+        error: std::num::ParseFloatError,
+        line: usize,
+        value: String,
+    },
     InvalidDocumentFormat,
     Custom(String),
     JsonError(serde_json::Error),
@@ -117,16 +121,10 @@ impl From<serde_json::Error> for Error {
     }
 }
 
-impl From<ParseFloatError> for Error {
-    fn from(other: ParseFloatError) -> Self {
-        Self::ParseFloat(other)
-    }
-}
-
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            Error::ParseFloat(e) => write!(f, "{}", e),
+            Error::ParseFloat { error, line, value} => write!(f, "Error parsing number {:?} at line {}: {}", value, line, error),
             Error::Custom(s) => write!(f, "Unexpected serialization error: {}", s),
             Error::InvalidDocumentFormat => f.write_str("Invalid document addition format."),
             Error::JsonError(err) => write!(f, "Couldn't serialize document value: {}", err),