keymgr: Add a Keystore::contains accessor.

crates/tor-keymgr/semver.md

@@ -12,4 +12,4 @@ BREAKING: `KeyMgr::insert`, `KeyMgr::remove` now take an
 REMOVED: the `has_key_bundle` function (from the `Keystore` trait)
 ADDED: `PartialEq`, `Eq`, `Hash` derives for `ArtiPath` and `KeyType`
 ADDED: a `to_bytes` function to `EncodableKey` trait
-
+ADDED: `Keystore::contains()`

crates/tor-keymgr/src/keystore.rs

@@ -26,6 +26,9 @@ pub trait Keystore: Send + Sync + 'static {
     /// store.
     fn id(&self) -> &KeystoreId;
 
+    /// Check if the the key identified by `key_spec` exists in this key store.
+    fn contains(&self, key_spec: &dyn KeySpecifier, key_type: KeyType) -> Result<bool>;
+
     /// Retrieve the key identified by `key_spec`.
     ///
     /// Returns `Ok(Some(key))` if the key was successfully retrieved. Returns `Ok(None)` if the

crates/tor-keymgr/src/keystore/arti.rs

@@ -68,6 +68,10 @@ impl Keystore for ArtiNativeKeystore {
         &self.id
     }
 
+    fn contains(&self, key_spec: &dyn KeySpecifier, key_type: KeyType) -> Result<bool> {
+        Ok(self.key_path(key_spec, key_type)?.exists())
+    }
+
     fn get(&self, key_spec: &dyn KeySpecifier, key_type: KeyType) -> Result<Option<ErasedKey>> {
         let path = self.key_path(key_spec, key_type)?;
 

crates/tor-keymgr/src/mgr.rs

@@ -210,6 +210,14 @@ mod tests {
             }
 
             impl Keystore for $name {
+                fn contains(&self, key_spec: &dyn KeySpecifier, key_type: KeyType) -> Result<bool> {
+                    Ok(self
+                        .inner
+                        .read()
+                        .unwrap()
+                        .contains_key(&(key_spec.arti_path()?, key_type)))
+                }
+
                 fn id(&self) -> &KeystoreId {
                     &self.id
                 }
@@ -363,6 +371,10 @@ mod tests {
             vec![Keystore2::new_boxed(), Keystore3::new_boxed()],
         );
 
+        assert!(!mgr.key_stores[0]
+            .contains(&TestKeySpecifier1, TestKey::key_type())
+            .unwrap());
+
         // Insert a key into Keystore2
         mgr.insert(
             "coot".to_string(),
@@ -382,6 +394,10 @@ mod tests {
                 KeystoreSelector::Id(&KeystoreId::from_str("not_an_id_we_know_of").unwrap())
             )
             .is_err());
+        // The key still exists in Keystore2
+        assert!(mgr.key_stores[0]
+            .contains(&TestKeySpecifier1, TestKey::key_type())
+            .unwrap());
 
         // Try to remove the key from the default key store
         assert_eq!(
@@ -390,6 +406,11 @@ mod tests {
             None
         );
 
+        // The key still exists in Keystore2
+        assert!(mgr.key_stores[0]
+            .contains(&TestKeySpecifier1, TestKey::key_type())
+            .unwrap());
+
         // Removing from Keystore2 should succeed.
         assert_eq!(
             mgr.remove::<TestKey>(
@@ -399,5 +420,10 @@ mod tests {
             .unwrap(),
             Some(())
         );
+
+        // The key doesn't exist in Keystore2 anymore
+        assert!(!mgr.key_stores[0]
+            .contains(&TestKeySpecifier1, TestKey::key_type())
+            .unwrap());
     }
 }