serde-metadata: serialize metadata

Cargo.toml

@@ -22,3 +22,4 @@ darling = "0.20"
 quote = "1"
 syn = "2"
 proc-macro2 = "1"
+insta = "1"

flake.nix

@@ -103,6 +103,7 @@
             my-rust
             pkgs.taplo
             pkgs.cargo-deny
+            pkgs.cargo-insta
           ];
         };
       };

serde-metadata/Cargo.toml

@@ -8,4 +8,8 @@ homepage = { workspace = true }
 
 [dependencies]
 indexmap = { workspace = true, features = ["serde"] }
-serde = { workspace = true }
+serde = { workspace = true, features = ["derive"] }
+
+[dev-dependencies]
+insta = { workspace = true }
+serde_json = { workspace = true }

serde-metadata/src/lib.rs

@@ -7,14 +7,30 @@ use serde::Serialize;
 pub struct Metadata {
     items: IndexMap<String, String>,
 }
+impl Metadata {
+    pub fn new() -> Self {
+        Self {
+            items: IndexMap::new(),
+        }
+    }
+}
 impl Deref for Metadata {
     type Target = IndexMap<String, String>;
 
     fn deref(&self) -> &Self::Target {
         &self.items
     }
 }
+impl From<IndexMap<String, String>> for Metadata {
+    fn from(items: IndexMap<String, String>) -> Self {
+        Self { items }
+    }
+}
 
 pub trait SerdeMetadata: Serialize {
     type METADATA: Serialize + Default;
+
+    fn get_metadata(&self) -> Self::METADATA {
+        Self::METADATA::default()
+    }
 }

serde-metadata/tests/simple.rs

@@ -1,3 +1,4 @@
+use indexmap::indexmap;
 use serde::Serialize;
 use serde_metadata::{Metadata, SerdeMetadata};
 
@@ -15,8 +16,12 @@ pub struct SimpleMetadata {
 impl Default for SimpleMetadata {
     fn default() -> Self {
         Self {
-            a: Default::default(),
-            b: Default::default(),
+            a: Metadata::from(indexmap! {
+                "comment".to_string() => "field: a".to_string(),
+            }),
+            b: Metadata::from(indexmap! {
+                "comment".to_string() => "field: b".to_string(),
+            }),
         }
     }
 }
@@ -27,4 +32,11 @@ impl SerdeMetadata for Simple {
 
 #[test]
 fn get_metadata() {
+    let simple = Simple {
+        a: "hello".to_string(),
+        b: 42,
+    };
+    let metadata = simple.get_metadata();
+
+    insta::assert_snapshot!(serde_json::to_string(&metadata).unwrap());
 }

serde-metadata/tests/snapshots/simple__get_metadata.snap

@@ -0,0 +1,5 @@
+---
+source: serde-metadata/tests/simple.rs
+expression: "serde_json::to_string(&metadata).unwrap()"
+---
+{"a":{"items":{"comment":"field: a"}},"b":{"items":{"comment":"field: b"}}}