feat(deployment): let an ungated resource link a gated one

crates/alien-core/src/lib.rs

@@ -12,6 +12,8 @@ pub use permissions::*;
 mod platform;
 pub use platform::*;
 
+mod resource_links;
+pub use resource_links::*;
 mod secret_delivery;
 pub use secret_delivery::*;
 

crates/alien-core/src/resource_links.rs

@@ -0,0 +1,305 @@
+//! Resources that own links to other resources.
+//!
+//! A link produces an `ALIEN_<ID>_BINDING` and is the one reference kind a declined gate can
+//! remove; structural edges cannot. Resolution is by concrete type, not by tag string.
+
+use crate::resource::{Resource, ResourceRef};
+use crate::resources::{Build, Container, Daemon, Worker};
+
+/// A resource definition that owns resource links.
+pub trait ResourceLinks {
+    /// The links this definition owns, excluding triggers and ordering edges.
+    fn links(&self) -> &[ResourceRef];
+
+    /// Mutable access, for dropping links to resources leaving the stack.
+    fn links_mut(&mut self) -> &mut Vec<ResourceRef>;
+}
+
+macro_rules! impl_resource_links {
+    ($($ty:ty),+ $(,)?) => {$(
+        impl ResourceLinks for $ty {
+            fn links(&self) -> &[ResourceRef] {
+                &self.links
+            }
+
+            fn links_mut(&mut self) -> &mut Vec<ResourceRef> {
+                &mut self.links
+            }
+        }
+    )+};
+}
+
+impl_resource_links!(Worker, Container, Daemon, Build);
+
+
+
+/// The link-owning view of a resource, or `None` when it owns no links.
+///
+/// `None` is ordinary and callers walking every resource skip it; a caller that has already
+/// established it holds a link owner should fail loudly instead.
+pub fn resource_links(resource: &Resource) -> Option<&dyn ResourceLinks> {
+    if let Some(worker) = resource.downcast_ref::<Worker>() {
+        return Some(worker);
+    }
+    if let Some(container) = resource.downcast_ref::<Container>() {
+        return Some(container);
+    }
+    if let Some(daemon) = resource.downcast_ref::<Daemon>() {
+        return Some(daemon);
+    }
+    // Build is not a compute kind, but it owns author-declared links producing the same
+    // bindings, so a declined gate must reach them too. Strip timing follows the target's
+    // lifecycle, not Build's, so a Build linking a live-gated target takes the late strip.
+    if let Some(build) = resource.downcast_ref::<Build>() {
+        return Some(build);
+    }
+    None
+}
+
+/// Mutable counterpart of [`resource_links`].
+pub fn resource_links_mut(resource: &mut Resource) -> Option<&mut dyn ResourceLinks> {
+    // Probed immutably first: returning a `&mut` borrow out of a conditional keeps the
+    // borrow alive across the whole function, which rejects a downcast chain.
+    if resource.downcast_ref::<Worker>().is_some() {
+        return resource
+            .downcast_mut::<Worker>()
+            .map(|worker| worker as &mut dyn ResourceLinks);
+    }
+    if resource.downcast_ref::<Container>().is_some() {
+        return resource
+            .downcast_mut::<Container>()
+            .map(|container| container as &mut dyn ResourceLinks);
+    }
+    if resource.downcast_ref::<Daemon>().is_some() {
+        return resource
+            .downcast_mut::<Daemon>()
+            .map(|daemon| daemon as &mut dyn ResourceLinks);
+    }
+    if resource.downcast_ref::<Build>().is_some() {
+        return resource
+            .downcast_mut::<Build>()
+            .map(|build| build as &mut dyn ResourceLinks);
+    }
+    None
+}
+
+/// The links a resource owns, empty when it owns none.
+pub fn links_of(resource: &Resource) -> &[ResourceRef] {
+    resource_links(resource).map_or(&[], |owner| owner.links())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::resources::{ContainerCode, DaemonCode, Kv, ResourceSpec, WorkerCode};
+    use serde::Deserialize;
+
+    fn kv(id: &str) -> Kv {
+        Kv::new(id.to_string()).build()
+    }
+
+    fn worker() -> Resource {
+        Resource::new(
+            Worker::new("api".to_string())
+                .permissions("execution".to_string())
+                .code(WorkerCode::Image {
+                    image: "example.com/api:latest".to_string(),
+                })
+                .link(&kv("cache"))
+                .link(&kv("store"))
+                .build(),
+        )
+    }
+
+    fn container() -> Resource {
+        Resource::new(
+            Container::new("api".to_string())
+                .code(ContainerCode::Image {
+                    image: "example.com/api:latest".to_string(),
+                })
+                .cpu(ResourceSpec {
+                    min: "0.25".to_string(),
+                    desired: "0.5".to_string(),
+                })
+                .memory(ResourceSpec {
+                    min: "256Mi".to_string(),
+                    desired: "512Mi".to_string(),
+                })
+                .replicas(1)
+                .permissions("execution".to_string())
+                .port(8080)
+                .link(&kv("cache"))
+                .link(&kv("store"))
+                .build(),
+        )
+    }
+
+    fn daemon() -> Resource {
+        Resource::new(
+            Daemon::new("agent".to_string())
+                .code(DaemonCode::Image {
+                    image: "example.com/agent:latest".to_string(),
+                })
+                .cluster("runtime".to_string())
+                .permissions("execution".to_string())
+                .link(&kv("cache"))
+                .link(&kv("store"))
+                .build(),
+        )
+    }
+
+    fn build() -> Resource {
+        Resource::new(
+            Build::new("builder".to_string())
+                .permissions("build".to_string())
+                .link(&kv("cache"))
+                .link(&kv("store"))
+                .build(),
+        )
+    }
+
+    /// One entry per wired link owner. The resolve, scrub and drift tests all read this, so
+    /// adding a type is a single edit rather than several independently-trusted ones.
+    const FIXTURES: &[(&str, fn() -> Resource)] = &[
+        ("worker", worker),
+        ("container", container),
+        ("daemon", daemon),
+        ("build", build),
+    ];
+
+    /// Every link owner must resolve, expose its links, and drop exactly the named one.
+    /// Parametrised because a type that silently stops participating would otherwise only
+    /// surface as a dangling reference in a customer's account.
+    #[test]
+    fn every_link_owner_resolves_and_scrubs() {
+        for (name, make) in FIXTURES {
+            let mut resource = make();
+            assert_eq!(
+                links_of(&resource).len(),
+                2,
+                "{name} should start with both links"
+            );
+
+            let owner = resource_links_mut(&mut resource)
+                .unwrap_or_else(|| panic!("{name} must resolve as a link owner"));
+            owner.links_mut().retain(|l| l.id != "cache");
+
+            let remaining: Vec<&str> = links_of(&resource).iter().map(|l| l.id.as_str()).collect();
+            assert_eq!(remaining, vec!["store"], "{name} kept the wrong link");
+        }
+    }
+
+    /// Accepting must leave every link in place, or the scrub would be removing links it
+    /// was never asked to remove.
+    #[test]
+    fn no_declines_leaves_every_link_owner_untouched() {
+        for (name, make) in FIXTURES {
+            let mut resource = make();
+            let before: Vec<ResourceRef> = links_of(&resource).to_vec();
+            assert_eq!(before.len(), 2, "{name} should start with both links");
+            // Resolved strictly: behind an `if let` a broken resolver would skip the
+            // mutation entirely and the equality below would still hold.
+            let owner = resource_links_mut(&mut resource)
+                .unwrap_or_else(|| panic!("{name} must resolve as a link owner"));
+            let declined: Vec<String> = Vec::new();
+            owner.links_mut().retain(|l| !declined.contains(&l.id));
+            assert_eq!(links_of(&resource), before.as_slice(), "{name} changed");
+        }
+    }
+
+    /// A resource that owns no links resolves to `None` rather than an empty owner, so a
+    /// caller that requires one can fail loudly instead of silently seeing zero links.
+    #[test]
+    fn a_non_link_owner_does_not_resolve() {
+        let mut store = Resource::new(Kv::new("store".to_string()).build());
+
+        assert!(resource_links(&store).is_none());
+        assert!(resource_links_mut(&mut store).is_none());
+        assert!(links_of(&store).is_empty());
+    }
+
+    /// Every resource type the deserializer accepts, and whether it owns links.
+    ///
+    /// The `Deserialize for Resource` match is the registry; this only records classification.
+    const LINK_OWNERSHIP: &[(&str, bool)] = &[
+        ("worker", true),
+        ("container", true),
+        ("daemon", true),
+        ("build", true),
+        ("vault", false),
+        ("compute-cluster", false),
+        ("kubernetes-cluster", false),
+        ("storage", false),
+        ("queue", false),
+        ("email", false),
+        ("kv", false),
+        ("postgres", false),
+        ("network", false),
+        ("service-account", false),
+        ("artifact-registry", false),
+        ("service_activation", false),
+        ("remote-stack-management", false),
+        ("azure_resource_group", false),
+        ("azure_storage_account", false),
+        ("azure_container_apps_environment", false),
+        ("azure_service_bus_namespace", false),
+        ("experimental/aws-opensearch", false),
+    ];
+
+    /// Drift guard. The registered types are read out of the deserializer's own
+    /// `unknown_variant` refusal rather than restated, so a new type that never declares
+    /// whether it owns links fails here instead of silently opting out of scrubbing.
+    #[test]
+    fn every_registered_resource_type_declares_link_ownership() {
+        let refusal = Resource::deserialize(serde_json::json!({ "type": "not-a-resource" }))
+            .expect_err("an unregistered type must be refused");
+        let message = refusal.to_string();
+
+        let registered: Vec<&str> = message
+            .split('`')
+            .skip(1)
+            .step_by(2)
+            .filter(|tag| *tag != "not-a-resource")
+            .collect();
+
+        assert!(
+            registered.len() > 10,
+            "could not read the registered types out of: {message}"
+        );
+
+        for tag in &registered {
+            assert!(
+                LINK_OWNERSHIP.iter().any(|(known, _)| known == tag),
+                "resource type '{tag}' is registered but does not declare whether it owns \
+                 links. Add it to LINK_OWNERSHIP in resource_links.rs"
+            );
+        }
+
+        for (tag, _) in LINK_OWNERSHIP {
+            assert!(
+                registered.contains(tag),
+                "'{tag}' is classified but no longer registered; drop it from LINK_OWNERSHIP"
+            );
+        }
+
+        // Presence alone would pass a type declared `true` that nobody wired into
+        // `impl_resource_links!`, which then never resolves and is never scrubbed.
+        let declared: Vec<&str> = LINK_OWNERSHIP
+            .iter()
+            .filter(|(_, owns)| *owns)
+            .map(|(tag, _)| *tag)
+            .collect();
+        for (tag, make) in FIXTURES {
+            assert!(declared.contains(tag), "fixture '{tag}' is not declared a link owner");
+            assert!(
+                resource_links(&make()).is_some(),
+                "'{tag}' is declared a link owner but does not resolve as one"
+            );
+        }
+        assert_eq!(
+            declared.len(),
+            FIXTURES.len(),
+            "declared link owners {declared:?} have no fixture proving they resolve"
+        );
+    }
+}