ostree-ext/json: add JsonOrderedSerialize trait

serde_json doesn't enforce any ordering when serializing HashMap

Signed-off-by: Etienne Champetier <[email protected]>

Author: champtar

ostree-ext/src/json.rs

@@ -0,0 +1,32 @@
+use anyhow::Result;
+use olpc_cjson::CanonicalFormatter;
+use std::io;
+
+pub(crate) trait JsonOrderedSerialize {
+    fn to_json_canonical_string(&self) -> Result<String>;
+    fn to_json_canonical_writer<W>(&self, writer: W) -> Result<()>
+    where
+        W: io::Write;
+}
+
+impl<S> JsonOrderedSerialize for S
+where
+    S: serde::ser::Serialize,
+{
+    fn to_json_canonical_string(&self) -> Result<String> {
+        let mut ser = serde_json::Serializer::with_formatter(Vec::new(), CanonicalFormatter::new());
+        self.serialize(&mut ser)?;
+        let str = String::from_utf8(ser.into_inner())?;
+        Ok(str)
+    }
+
+    fn to_json_canonical_writer<W>(&self, writer: W) -> Result<()>
+    where
+        W: io::Write,
+    {
+        let mut ser = serde_json::Serializer::with_formatter(writer, CanonicalFormatter::new());
+        self.serialize(&mut ser)?;
+        ser.into_inner().flush()?;
+        Ok(())
+    }
+}

ostree-ext/src/lib.rs

@@ -61,6 +61,7 @@ pub(crate) mod ostree_manual;
 
 pub(crate) mod statistics;
 
+mod json;
 mod utils;
 
 #[cfg(feature = "docgen")]