chore: simplify compare_policy_report.py to be compatible with python36

Signed-off-by: Nathan Nguyen <[email protected]>

tests/policy_engine/compare_policy_reports.py

@@ -3,7 +3,11 @@
 # Copyright (c) 2023 - 2023, Oracle and/or its affiliates. All rights reserved.
 # Licensed under the Universal Permissive License v 1.0 as shown at https://oss.oracle.com/licenses/upl/.
 
-"""This module checks the policy engine report against expected results."""
+"""This script checks the policy engine report against expected results.
+
+Note: Make sure that this script is compatible with Python 3.6 (system python version on OL8).
+"""
+
 import json
 import logging
 import sys
@@ -15,7 +19,7 @@
 logger.setLevel(logging.DEBUG)
 
 
-def check_policies(results: list, expectations: list) -> bool:
+def check_policies(results: list, expectations: list) -> str | None:
     """
     Compare result policies against expected policies.
 
@@ -28,12 +32,9 @@ def check_policies(results: list, expectations: list) -> bool:
 
     Returns
     -------
-    bool
-        Returns True if successful.
-
-    Raises
-    ------
-    ValueError
+    str | None
+        Returns an error message if ``results`` do not match ``expectations``.
+        Returns ``None`` otherwise.
     """
     # If not empty, policy is always a list with one item.
     # For example, Datalog declaration for failed_policies is `failed_policies(policy_id: symbol)`.
@@ -42,22 +43,25 @@ def check_policies(results: list, expectations: list) -> bool:
         # Iterate through the rows returned by the policy engine.
         for index, exp in enumerate(expectations):
             res = results[index]
-            if (fails := abs(len(res) - len(exp))) > 0:
+
+            fails = abs(len(res) - len(exp))
+            if fails > 0:
                 fail_count += fails
                 continue
+
             # Do not check the first element, which is the primary key.
             c_fail = Counter(exp[1:])
             c_fail.subtract(Counter(res[1:]))
-            if (fails := len([value for value in c_fail.values() if value != 0])) > 0:
+
+            fails = len([value for value in c_fail.values() if value != 0])
+            if fails > 0:
                 fail_count += fails
     else:
         fail_count += abs(len(results) - len(expectations))
 
     if fail_count > 0:
-        raise ValueError(
-            f"Results do not match in {fail_count} item(s): Result is {results} but expected {expectations}"
-        )
-    return True
+        return f"Results do not match in {fail_count} item(s): Result is {results} but expected {expectations}"
+    return None
 
 
 def main() -> int:
@@ -67,34 +71,29 @@ def main() -> int:
         with open(sys.argv[1], encoding="utf8") as res_file, open(sys.argv[2], encoding="utf8") as exp_file:
             result = json.load(res_file)
             expected = json.load(exp_file)
-
-            try:
-                check_policies(result["failed_policies"], expected["failed_policies"])
-            except ValueError as error:
-                return_code = 1
-                logger.error("failed_policies: %s", error)
-
-            try:
-                check_policies(result["passed_policies"], expected["passed_policies"])
-            except ValueError as error:
-                return_code = 1
-                logger.error("passed_policies: %s", error)
-
-            try:
-                check_policies(result["component_violates_policy"], expected["component_violates_policy"])
-            except ValueError as error:
-                return_code = 1
-                logger.error("component_violates_policy: %s", error)
-
-            try:
-                check_policies(result["component_satisfies_policy"], expected["component_satisfies_policy"])
-            except ValueError as error:
-                return_code = 1
-                logger.error("component_satisfies_policy: %s", error)
-
     except FileNotFoundError as error:
         logger.error(error)
+        return 1
+
+    error_msg = check_policies(result["failed_policies"], expected["failed_policies"])
+    if error_msg:
+        return_code = 1
+        logger.error("failed_policies: %s", error_msg)
+
+    error_msg = check_policies(result["passed_policies"], expected["passed_policies"])
+    if error_msg:
+        return_code = 1
+        logger.error("passed_policies: %s", error_msg)
+
+    error_msg = check_policies(result["component_violates_policy"], expected["component_violates_policy"])
+    if error_msg:
+        return_code = 1
+        logger.error("component_violates_policy: %s", error_msg)
+
+    error_msg = check_policies(result["component_satisfies_policy"], expected["component_satisfies_policy"])
+    if error_msg:
         return_code = 1
+        logger.error("component_satisfies_policy: %s", error_msg)
 
     return return_code