push green meta builds to the attic cache and record cached

swarm-wire/src/agent_closures.rs

@@ -32,6 +32,10 @@ pub struct AgentClosure {
     pub system: String,
     /// When the controller recorded the build, in unix seconds.
     pub built_unix: i64,
+    /// Whether the builder pushed the closure to the binary cache. A record
+    /// written before the field existed reads as false.
+    #[serde(default)]
+    pub cached: bool,
 }
 
 #[cfg(test)]
@@ -51,12 +55,14 @@ mod tests {
             store_path: "/nix/store/x".to_owned(),
             system: "x86_64-linux".to_owned(),
             built_unix: 7,
+            cached: true,
         };
         let wire = serde_json::json!({
             "meta_rev": "abc",
             "store_path": "/nix/store/x",
             "system": "x86_64-linux",
             "built_unix": 7,
+            "cached": true,
         });
         assert_eq!(serde_json::to_value(&value).expect("encodes"), wire);
         assert_eq!(
@@ -64,4 +70,16 @@ mod tests {
             value
         );
     }
+
+    #[test]
+    fn a_record_without_the_field_reads_as_not_cached() {
+        let old = serde_json::json!({
+            "meta_rev": "abc",
+            "store_path": "/nix/store/x",
+            "system": "x86_64-linux",
+            "built_unix": 7,
+        });
+        let record = serde_json::from_value::<AgentClosure>(old).expect("decodes");
+        assert!(!record.cached);
+    }
 }