fix: respect QuoteStyle::Never for empty fields

csv-core/src/lib.rs

@@ -142,7 +142,7 @@ impl Terminator {
 }
 
 /// The quoting style to use when writing CSV data.
-#[derive(Clone, Copy, Debug, Default)]
+#[derive(Clone, Copy, Debug, Default, PartialEq)]
 #[non_exhaustive]
 pub enum QuoteStyle {
     /// This puts quotes around every field. Always.

csv-core/src/writer.rs

@@ -246,7 +246,10 @@ impl Writer {
     /// In particular, it will write closing quotes if necessary.
     pub fn finish(&mut self, mut output: &mut [u8]) -> (WriteResult, usize) {
         let mut nout = 0;
-        if self.state.record_bytes == 0 && self.state.in_field {
+        if self.state.record_bytes == 0
+            && self.state.in_field
+            && self.style != QuoteStyle::Never
+        {
             assert!(!self.state.quoting);
             let (res, o) = self.write(&[self.quote, self.quote], output);
             if o == 0 {
@@ -368,7 +371,7 @@ impl Writer {
         mut output: &mut [u8],
     ) -> (WriteResult, usize) {
         let mut nout = 0;
-        if self.state.record_bytes == 0 {
+        if self.state.record_bytes == 0 && self.style != QuoteStyle::Never {
             assert!(!self.state.quoting);
             let (res, o) = self.write(&[self.quote, self.quote], output);
             if o == 0 {
@@ -1075,4 +1078,24 @@ mod tests {
         );
         assert_write!(wtr, finish, &mut out[..], 1, InputEmpty, "\"");
     }
+
+    #[test]
+    fn never_quote_empty_field_terminator() {
+        let mut wtr =
+            WriterBuilder::new().quote_style(QuoteStyle::Never).build();
+        let out = &mut [0; 1024];
+
+        assert_field!(wtr, b(""), &mut out[..], 0, 0, InputEmpty, "");
+        assert_write!(wtr, terminator, &mut out[..], 1, InputEmpty, "\n");
+    }
+
+    #[test]
+    fn never_quote_empty_field_finish() {
+        let mut wtr =
+            WriterBuilder::new().quote_style(QuoteStyle::Never).build();
+        let out = &mut [0; 1024];
+
+        assert_field!(wtr, b(""), &mut out[..], 0, 0, InputEmpty, "");
+        assert_write!(wtr, finish, &mut out[..], 0, InputEmpty, "");
+    }
 }

src/writer.rs

@@ -1223,6 +1223,7 @@ mod tests {
     };
 
     use super::{Writer, WriterBuilder};
+    use crate::QuoteStyle;
 
     fn wtr_as_string(wtr: Writer<Vec<u8>>) -> String {
         String::from_utf8(wtr.into_inner().unwrap()).unwrap()
@@ -1450,4 +1451,15 @@ mod tests {
         let buf = wtr.into_inner().unwrap();
         assert_eq!(String::from_utf8(buf).unwrap(), "\"# comment\",another\n");
     }
+
+    #[test]
+    fn never_quote_empty_field() {
+        let mut wtr = WriterBuilder::new()
+            .quote_style(QuoteStyle::Never)
+            .from_writer(vec![]);
+        wtr.write_record(["foo"]).unwrap();
+        wtr.write_record([""]).unwrap();
+        wtr.write_record(["bar,baz"]).unwrap();
+        assert_eq!(wtr_as_string(wtr), "foo\n\nbar,baz\n");
+    }
 }