add a per-agent nix builds mode, host or none, carried like privateUsers

swarm-wire/src/agent_closures.rs

@@ -9,6 +9,8 @@
 //! Keyed by the agent alone, like [`crate::agent_limits`]: an agent can move
 //! between hives, and its closure goes with it.
 
+use hive_types::NixBuilds;
+
 /// The KV bucket closures are recorded in, keyed by agent name.
 pub const BUCKET: &str = "agent-closures";
 
@@ -42,6 +44,11 @@ pub struct AgentClosure {
     /// false, which keeps the agent out of one.
     #[serde(default)]
     pub private_users: bool,
+    /// The agent's `services.hyperhive.agent.nixBuilds`: where its nix builds
+    /// run. A record written before the field existed reads as
+    /// [`NixBuilds::Host`], which is what every agent did before it.
+    #[serde(default)]
+    pub nix_builds: NixBuilds,
 }
 
 #[cfg(test)]
@@ -63,6 +70,7 @@ mod tests {
             built_unix: 7,
             cached: true,
             private_users: true,
+            nix_builds: NixBuilds::Disabled,
         };
         let wire = serde_json::json!({
             "meta_rev": "abc",
@@ -71,6 +79,7 @@ mod tests {
             "built_unix": 7,
             "cached": true,
             "private_users": true,
+            "nix_builds": "none",
         });
         assert_eq!(serde_json::to_value(&value).expect("encodes"), wire);
         assert_eq!(
@@ -80,7 +89,7 @@ mod tests {
     }
 
     #[test]
-    fn a_record_without_the_fields_reads_as_not_cached_and_not_namespaced() {
+    fn a_record_without_the_fields_reads_as_not_cached_not_namespaced_and_host_builds() {
         let old = serde_json::json!({
             "meta_rev": "abc",
             "store_path": "/nix/store/x",
@@ -90,5 +99,6 @@ mod tests {
         let record = serde_json::from_value::<AgentClosure>(old).expect("decodes");
         assert!(!record.cached);
         assert!(!record.private_users);
+        assert_eq!(record.nix_builds, NixBuilds::Host);
     }
 }