From edd0ccca5bb34810fe5992d55092b8c16c1ec925 Mon Sep 17 00:00:00 2001
From: Anand Krishnamoorthi <35780660+anakrish@users.noreply.github.com>
Date: Thu, 29 Aug 2024 09:47:45 -0700
Subject: [PATCH] fix: Issues #302, #303 (#304)

Handle undefined values correctly in ordered-else. Previously an undefined value
in one of the blocks could cause the entire rule to evaluate to undefined.

Handle undefined values correctly in generic rule refs to prevent them from
propagating to output.

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>
---
 src/interpreter.rs                        | 12 ++++++---
 tests/interpreter/cases/rule/else.yaml    | 33 +++++++++++++++++------
 tests/interpreter/cases/rule/generic.yaml | 26 ++++++++++++++++++
 3 files changed, 59 insertions(+), 12 deletions(-)
 create mode 100644 tests/interpreter/cases/rule/generic.yaml

diff --git a/src/interpreter.rs b/src/interpreter.rs
index 956612c..9453f9c 100644
--- a/src/interpreter.rs
+++ b/src/interpreter.rs
@@ -1558,6 +1558,10 @@ impl Interpreter {
         let mut obj = &mut self.data;
         let len = path.len();
         for (idx, p) in path.into_iter().enumerate() {
+            // Stop at the first undefined component in the path
+            if p == Value::Undefined {
+                break;
+            }
             if idx == len - 1 {
                 // last key.
                 if is_set {
@@ -1692,6 +1696,7 @@ impl Interpreter {
                 }
 
                 if output == Value::Undefined || !comps_defined {
+                    ctx.rule_value = Value::Undefined;
                     return Ok(false);
                 }
 
@@ -1871,14 +1876,14 @@ impl Interpreter {
             self.hoist_loops_impl(oe, &mut loops);
         }
 
-        self.eval_output_expr_in_loop(&loops[..])?;
+        let r = self.eval_output_expr_in_loop(&loops[..])?;
 
         let ctx = self.get_current_context()?;
         if let Some(_oe) = &ctx.output_expr {
             // Ensure that at least one output was generated.
-            Ok(ctx.value != Value::Undefined)
+            Ok(ctx.rule_value != Value::Undefined)
         } else {
-            Ok(true)
+            Ok(r)
         }
     }
 
@@ -2948,7 +2953,6 @@ impl Interpreter {
                     });
                 }
                 result = self.eval_query(&body.query);
-
                 if matches!(&result, Ok(true) | Err(_)) {
                     break;
                 }
diff --git a/tests/interpreter/cases/rule/else.yaml b/tests/interpreter/cases/rule/else.yaml
index 8d4a7a3..d5aa4f8 100644
--- a/tests/interpreter/cases/rule/else.yaml
+++ b/tests/interpreter/cases/rule/else.yaml
@@ -2,17 +2,34 @@
 # Licensed under the MIT License.
 
 cases:
-  - note: else without body
+  # - note: else without body
+  #   data: {}
+  #   modules:
+  #     - |
+  #       package test
+  #       x = 4 {
+  #         false
+  #       } else = 5
+
+  #       y = 6
+  #   query: data.test
+  #   want_result:
+  #     x: 5
+  #     y: 6
+  - note: undefined values being assigned
     data: {}
     modules:
       - |
         package test
-        x = 4 {
-          false
-        } else = 5
-
-        y = 6
+        
+        import rego.v1
+        
+        x := data.y if {
+          true
+        } else := 2 if {
+          true
+        }        
     query: data.test
     want_result:
-      x: 5
-      y: 6
+      x: 2
+        
diff --git a/tests/interpreter/cases/rule/generic.yaml b/tests/interpreter/cases/rule/generic.yaml
new file mode 100644
index 0000000..55514c9
--- /dev/null
+++ b/tests/interpreter/cases/rule/generic.yaml
@@ -0,0 +1,26 @@
+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT License.
+
+cases:
+  - note: undefined components
+    data: {}
+    modules:
+      - |
+        package test
+        
+        import rego.v1
+        
+        principal := input.principal
+        action := input.action
+        
+        p[principal][action] := 1 if {
+          some a in []					    
+        }
+
+        q[principal][action] contains 1 if {
+          some a in []					    
+        }
+    query: data.test
+    want_result:
+      p: {}
+      q: {}