feat: expose precise observations for synchronous read-only calls

crates/core/src/eval.rs

@@ -59,9 +59,23 @@ impl Vm {
         arguments: &[Value],
         limits: ExecutionLimits,
     ) -> Result<(Value, Vec<ObjectRef>), VmError> {
+        let (value, reads) =
+            self.call_read_only_precise_with_limits(function, arguments, limits)?;
+        Ok((value, reads.objects))
+    }
+
+    /// Synchronous read-only call with precise observations as well as the
+    /// conservative object list. Result ownership and hard limits match call().
+    /// ReadSet and all identities/value snapshots inside it are borrowed only.
+    pub fn call_read_only_precise_with_limits(
+        &mut self,
+        function: ObjectRef,
+        arguments: &[Value],
+        limits: ExecutionLimits,
+    ) -> Result<(Value, crate::ReadSet), VmError> {
         let scope = self.objects.begin_read_only();
         let result = self.call_with_limits(function, arguments, limits);
-        let reads = self.objects.end_read_only(scope)?;
+        let reads = self.objects.end_read_only_precise(scope)?;
         result.map(|value| (value, reads))
     }
 

crates/core/tests/execution.rs

@@ -1749,6 +1749,18 @@ fn named_reads_ignore_unrelated_globals_but_track_missing_shadow_and_payload_kin
     assert!(reads.contains(&globals) && reads.contains(&builtins));
     vm.release_value(value).unwrap();
     vm.dict_set(globals, text("_"), text("unrelated")).unwrap();
+    let (value, synchronous) = vm
+        .call_read_only_precise_with_limits(function, &[], ExecutionLimits::default())
+        .unwrap();
+    assert_eq!(value, text("builtin"));
+    assert_eq!(synchronous.dependencies, dependencies);
+    assert_eq!(synchronous.objects, reads);
+    vm.release_value(value).unwrap();
+    let (value, conservative) = vm
+        .call_read_only_with_limits(function, &[], ExecutionLimits::default())
+        .unwrap();
+    assert_eq!(conservative, reads);
+    vm.release_value(value).unwrap();
     assert!(
         dependencies
             .iter()