Fix target-aware prepare path and add regression test

Agent-Logs-Url: https://github.com/microsoft/regorus/sessions/f964122b-5af3-41a7-bc51-d87b7271a455

Co-authored-by: anakrish <35780660+anakrish@users.noreply.github.com>

tests/engine/mod.rs

@@ -142,6 +142,46 @@ fn prepare_then_clone_without_initial_eval() -> Result<()> {
     Ok(())
 }
 
+#[test]
+#[cfg(feature = "azure_policy")]
+#[cfg_attr(docsrs, doc(cfg(feature = "azure_policy")))]
+fn prepare_then_compile_for_target() -> Result<()> {
+    if !registry::targets::contains("target.tests.sample_test_target") {
+        let target = Target::from_json_str(include_str!(
+            "../interpreter/cases/target/definitions/sample_target.json"
+        ))?;
+        registry::targets::register(Rc::new(target))?;
+    }
+
+    let mut engine = Engine::new();
+    engine.add_policy(
+        "test.rego".to_string(),
+        r#"package test
+           import rego.v1
+           __target__ := "target.tests.sample_test_target"
+
+           default allow := false
+
+           allow if {
+             input.type == "test_resource"
+           }
+        "#
+        .to_string(),
+    )?;
+
+    engine.prepare()?;
+    let compiled = engine.compile_for_target()?;
+    let info = compiled.get_policy_info()?;
+    assert_eq!(info.target_name.as_deref(), Some("target.tests.sample_test_target"));
+
+    let result = compiled.eval_with_input(Value::from_json_str(
+        r#"{"name":"resource-1","type":"test_resource"}"#,
+    )?)?;
+    assert_eq!(result, Value::from(true));
+
+    Ok(())
+}
+
 #[test]
 #[cfg(feature = "azure_policy")]
 #[cfg_attr(docsrs, doc(cfg(feature = "azure_policy")))]