Fix a regression in codec configuration serialisation with an empty c…

…onfiguration

This fixes a regression introduced in v0.11.2 (89fc63f)

CHANGELOG.md

@@ -10,6 +10,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
  - Add `codecov` support to CI
 
+### Fixed
+  - Fixed a regression introduced in v0.11.2 ([89fc63f](https://github.com/LDeakin/zarrs/commit/89fc63fa318cfd780e85fec6f9506ca65336a2c3)) where codecs with an empty configuration would serialise as a string rather than a struct with a `name` field, which goes against the zarr spec
+    - Fixes the `codec_bytes_configuration_none` test and adds `codec_crc32c_configuration_none` test
+
 ## [0.11.3] - 2024-01-31
 
 ### Added

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "zarrs"
-version = "0.11.3"
+version = "0.11.4"
 authors = ["Lachlan Deakin <[email protected]>"]
 edition = "2021"
 rust-version = "1.71"

src/array/codec/array_to_bytes/bytes.rs

@@ -156,7 +156,10 @@ mod tests {
         let codec_configuration: BytesCodecConfiguration = serde_json::from_str(r#"{}"#).unwrap();
         let codec = BytesCodec::new_with_configuration(&codec_configuration);
         let metadata = codec.create_metadata().unwrap();
-        assert_eq!(serde_json::to_string(&metadata).unwrap(), r#""bytes""#);
+        assert_eq!(
+            serde_json::to_string(&metadata).unwrap(),
+            r#"{"name":"bytes"}"#
+        );
     }
 
     fn codec_bytes_round_trip_impl(

src/array/codec/bytes_to_bytes/crc32c.rs

@@ -45,14 +45,28 @@ const CHECKSUM_SIZE: usize = core::mem::size_of::<u32>();
 #[cfg(test)]
 mod tests {
     use crate::{
-        array::{codec::BytesToBytesCodecTraits, BytesRepresentation},
+        array::{
+            codec::{BytesToBytesCodecTraits, CodecTraits},
+            BytesRepresentation,
+        },
         byte_range::ByteRange,
     };
 
     use super::*;
 
     const JSON1: &str = r#"{}"#;
 
+    #[test]
+    fn codec_crc32c_configuration_none() {
+        let codec_configuration: Crc32cCodecConfiguration = serde_json::from_str(r#"{}"#).unwrap();
+        let codec = Crc32cCodec::new_with_configuration(&codec_configuration);
+        let metadata = codec.create_metadata().unwrap();
+        assert_eq!(
+            serde_json::to_string(&metadata).unwrap(),
+            r#"{"name":"crc32c"}"#
+        );
+    }
+
     #[test]
     fn codec_crc32c() {
         let elements: Vec<u8> = (0..6).collect();

src/metadata.rs

@@ -68,10 +68,16 @@ impl core::fmt::Display for Metadata {
 impl serde::Serialize for Metadata {
     fn serialize<S: serde::Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
         if let Some(configuration) = &self.configuration {
-            let mut s = s.serialize_map(Some(2))?;
-            s.serialize_entry("name", &self.name)?;
-            s.serialize_entry("configuration", configuration)?;
-            s.end()
+            if configuration.is_empty() {
+                let mut s = s.serialize_map(Some(1))?;
+                s.serialize_entry("name", &self.name)?;
+                s.end()
+            } else {
+                let mut s = s.serialize_map(Some(2))?;
+                s.serialize_entry("name", &self.name)?;
+                s.serialize_entry("configuration", configuration)?;
+                s.end()
+            }
         } else {
             s.serialize_str(self.name.as_str())
         }
@@ -140,11 +146,7 @@ impl Metadata {
     ) -> Result<Self, serde_json::Error> {
         let configuration = serde_json::to_value(configuration)?;
         if let serde_json::Value::Object(configuration) = configuration {
-            if configuration.is_empty() {
-                Ok(Self::new(name))
-            } else {
-                Ok(Self::new_with_configuration(name, configuration))
-            }
+            Ok(Self::new_with_configuration(name, configuration))
         } else {
             Err(serde::ser::Error::custom(
                 "the configuration cannot be serialized to a JSON struct",