fix: align protocol error semantics

crates/wip-host/src/lib.rs

@@ -545,9 +545,9 @@ pub trait ObjectProvider {
         self.with_object(path, PublishedObject::protocol_object)
             .ok_or_else(|| CallError::new(CallErrorKind::NotFound, "target path is not published"))
             .and_then(|object| {
-                object.validate_at_path(path).map_err(|error| {
-                    CallError::new(CallErrorKind::InvalidResult, error.to_string())
-                })?;
+                object
+                    .validate_at_path(path)
+                    .map_err(|error| CallError::new(CallErrorKind::Internal, error.to_string()))?;
                 Ok(object)
             })
     }
@@ -607,7 +607,9 @@ pub enum CallErrorKind {
     OperationNotFound,
     /// Supplied named values do not satisfy the operation declaration.
     InvalidArguments,
-    /// The encoded implementation result violates its declaration.
+    /// The Host constructed an invalid response before operation execution.
+    Internal,
+    /// The encoded implementation result violates its declaration after execution.
     InvalidResult,
     /// This operation requires a validator and the call omitted it.
     ValidatorRequired,
@@ -683,7 +685,10 @@ impl CallError {
             CallErrorKind::InterfaceMismatch => ProtocolErrorCode::InterfaceMismatch,
             CallErrorKind::OperationNotFound => ProtocolErrorCode::OperationNotFound,
             CallErrorKind::InvalidArguments => ProtocolErrorCode::InvalidArguments,
-            CallErrorKind::InvalidResult => ProtocolErrorCode::InvalidResult,
+            CallErrorKind::Internal => ProtocolErrorCode::Internal,
+            CallErrorKind::InvalidResult | CallErrorKind::Implementation => {
+                ProtocolErrorCode::OperationOutcomeUnknown
+            }
             CallErrorKind::ValidatorRequired => ProtocolErrorCode::ValidatorRequired,
             CallErrorKind::ValidatorMismatch => ProtocolErrorCode::ValidatorMismatch,
             CallErrorKind::InterfaceValidatorRequired => {
@@ -693,7 +698,6 @@ impl CallError {
                 ProtocolErrorCode::InterfaceValidatorMismatch
             }
             CallErrorKind::PermissionDenied => ProtocolErrorCode::PermissionDenied,
-            CallErrorKind::Implementation => ProtocolErrorCode::Internal,
         };
         ProtocolError {
             code,

crates/wip-host/tests/host.rs

@@ -235,6 +235,10 @@ impl ObjectProvider for TestProvider {
                 )
             }
             "/empty" => (Document::open("empty", None, Rc::clone(&self.calls)), 0),
+            "/invalid-object" => (
+                Document::open("wrong-name", None, Rc::clone(&self.calls)),
+                0,
+            ),
             "/broken" => (
                 Document::open("broken", Some("broken-ref"), Rc::clone(&self.calls)),
                 3,
@@ -624,9 +628,15 @@ fn immutable_interface_rejects_a_supplied_validator() {
 }
 
 #[test]
-fn invalid_results_and_backend_failures_keep_distinct_protocol_codes() {
+fn invalid_host_responses_and_uncertain_operation_failures_use_canonical_codes() {
     let (_, provider, _) = registry_and_provider();
 
+    assert_failure(
+        provider.fetch("/invalid-object").unwrap_err(),
+        CallErrorKind::Internal,
+        ProtocolErrorCode::Internal,
+    );
+
     assert_failure(
         provider
             .call_operation(request(
@@ -639,7 +649,7 @@ fn invalid_results_and_backend_failures_keep_distinct_protocol_codes() {
             ))
             .unwrap_err(),
         CallErrorKind::InvalidResult,
-        ProtocolErrorCode::InvalidResult,
+        ProtocolErrorCode::OperationOutcomeUnknown,
     );
     assert_failure(
         provider
@@ -653,6 +663,6 @@ fn invalid_results_and_backend_failures_keep_distinct_protocol_codes() {
             ))
             .unwrap_err(),
         CallErrorKind::Implementation,
-        ProtocolErrorCode::Internal,
+        ProtocolErrorCode::OperationOutcomeUnknown,
     );
 }