From 3f73d6ef2ac9b01b100f7fa15cadcc8cfa986a37 Mon Sep 17 00:00:00 2001
From: Ahmed Nafies <ahmed.nafies@gmail.com>
Date: Fri, 2 Feb 2024 00:42:26 +0100
Subject: [PATCH] feat: adds no match exceptions

---
 src/rules_engine/__init__.py | 20 +++++++++---------
 tests/test_operators.py      | 39 +++++++++++++++++++++++++++---------
 2 files changed, 40 insertions(+), 19 deletions(-)

diff --git a/src/rules_engine/__init__.py b/src/rules_engine/__init__.py
index 7ac154e..c1802de 100644
--- a/src/rules_engine/__init__.py
+++ b/src/rules_engine/__init__.py
@@ -4,6 +4,10 @@
 T = TypeVar('T')
 
 
+class NoMatch(Exception):
+    message = "No conditions matched"
+
+
 @dataclass
 class Result:
     value: Any
@@ -36,24 +40,22 @@ class RulesEngine:
     def __init__(self, *rules: Rule) -> None:
         self.rules = rules
 
-    def _get_message(self, rule) -> Optional[str]:
-        if rule.message:
-            return rule.message
-        return rule.condition.__name__ if rule.condition.__name__ != "<lambda>" else None
-
     def run(self, *args: Any, **kwargs: Any) -> Any:
         for rule in self.rules:
             if rule.condition(*args, **kwargs):
-                return Result(value=rule.action(*args, **kwargs), message=self._get_message(rule))
+                return Result(value=rule.action(*args, **kwargs), message=rule.message)
 
-        return Result(value=None, message="No conditions matched")
+        raise NoMatch
 
     def run_all(self, *args: Any, **kwargs: Any) -> list:
-        return [
-            Result(value=rule.action(*args, **kwargs), message=self._get_message(rule))
+        results = [
+            Result(value=rule.action(*args, **kwargs), message=rule.message)
             for rule in self.rules
             if rule.condition(*args, **kwargs)
         ]
+        if not results:
+            raise NoMatch
+        return results
 
 
 def when(state: bool) -> Callable[..., bool]:
diff --git a/tests/test_operators.py b/tests/test_operators.py
index 58d3d0c..a92d45b 100644
--- a/tests/test_operators.py
+++ b/tests/test_operators.py
@@ -1,6 +1,6 @@
 import pytest
 
-from src.rules_engine import Rule, RulesEngine, all_, any_, not_, then, when
+from src.rules_engine import NoMatch, Rule, RulesEngine, all_, any_, not_, then, when
 
 
 def raise_cannot_be_none_error(obj):
@@ -13,15 +13,13 @@ def test_when_then_operator():
     with pytest.raises(ValueError):
         RulesEngine(Rule(when(obj is None), raise_cannot_be_none_error)).run(obj)
 
-    result = RulesEngine(Rule(when(obj is not None), then(True), "obj is None")).run(obj)
-    assert result.value is None
-    assert result.message == "No conditions matched"
+    with pytest.raises(NoMatch):
+        RulesEngine(Rule(when(obj is not None), raise_cannot_be_none_error)).run(obj)
 
 
 @pytest.mark.parametrize(
     "condition,action,result",
     [
-        (True, True, None),
         (False, "A", "A"),
         (False, "B", "B"),
     ],
@@ -35,7 +33,6 @@ def test_not_operator(condition, action, result):
 @pytest.mark.parametrize(
     "conditions,action,result",
     [
-        ([when(False), when(False), when(False)], "A", None),
         ([when(True), when(False), when(False)], "A", "A"),
         ([when(True), when(True), when(False)], "A", "A"),
         ([when(True), when(True), when(True)], "A", "A"),
@@ -43,16 +40,24 @@ def test_not_operator(condition, action, result):
 )
 def test_any_operator(conditions, action, result):
     obj = None
-
     assert RulesEngine(Rule(any_(*conditions), then(action))).run(obj).value is result
 
 
+@pytest.mark.parametrize(
+    "conditions,action",
+    [
+        ([when(False), when(False), when(False)], "A"),
+    ],
+)
+def test_any_operator_no_match(conditions, action):
+    obj = None
+    with pytest.raises(NoMatch):
+        RulesEngine(Rule(any_(*conditions), then(action))).run(obj)
+
+
 @pytest.mark.parametrize(
     "conditions,action,value,message",
     [
-        ([when(False), when(False), when(False)], "A", None, "No conditions matched"),
-        ([when(True), when(False), when(False)], "A", None, "No conditions matched"),
-        ([when(True), when(True), when(False)], "A", None, "No conditions matched"),
         ([when(True), when(True), when(True)], "A", "A", None),
     ],
 )
@@ -62,3 +67,17 @@ def test_all_operator(conditions, action, value, message):
     result = RulesEngine(Rule(all_(*conditions), then(action))).run(obj)
     assert result.value == value
     assert result.message == message
+
+
+@pytest.mark.parametrize(
+    "conditions,action,value,message",
+    [
+        ([when(False), when(False), when(False)], "A", None, "No conditions matched"),
+        ([when(True), when(False), when(False)], "A", None, "No conditions matched"),
+        ([when(True), when(True), when(False)], "A", None, "No conditions matched"),
+    ],
+)
+def test_all_operator_no_match(conditions, action, value, message):
+    obj = None
+    with pytest.raises(NoMatch):
+        RulesEngine(Rule(all_(*conditions), then(action))).run(obj)