Fixed licensing dedup issue #67

Signed-off-by: Chin Yeung Li <tli@nexb.com>

Author: chinyeungli

src/license_expression/__init__.py

@@ -750,12 +750,33 @@ def dedup(self, expression):
             ),
         ):
             relation = exp.__class__.__name__
-            deduped = combine_expressions(
-                expressions,
-                relation=relation,
-                unique=True,
-                licensing=self,
-            )
+            # Flatten nested 'AND' expressions only (not OR) to maintain precedence
+            # Example: (A AND B) AND (C OR D) will become A AND B AND (C OR D)
+            # The OR will not be flattened to avoid changing the expression logic
+            if relation == "AND":
+                flattened = []
+                for e in expressions:
+                    if isinstance(e, self.AND):
+                        # Flatten nested ANDs by extending with their args
+                        flattened.extend(e.args)
+                    else:
+                        flattened.append(e)
+                expressions = flattened
+
+            unique_expressions = []
+            for e in expressions:
+                if e not in unique_expressions:
+                    unique_expressions.append(e)
+
+            if len(unique_expressions) == 1:
+                deduped = unique_expressions[0]
+            else:
+                deduped = combine_expressions(
+                    expressions,
+                    relation=relation,
+                    unique=True,
+                    licensing=self,
+                )
         else:
             raise ExpressionError(f"Unknown expression type: {expression!r}")
         return deduped

tests/test_license_expression.py

@@ -693,6 +693,20 @@ def test_dedup_expressions_can_be_simplified_2(self):
         expected = l.parse("(mit AND (mit OR bsd-new)) OR mit")
         assert result == expected
 
+    def test_dedup_expressions_can_be_simplified_3(self):
+        l = Licensing()
+        exp = "(gpl AND mit) AND mit AND (gpl OR mit)"
+        result = l.dedup(exp)
+        expected = l.parse("gpl AND mit AND (gpl OR mit)")
+        assert result == expected
+
+    def test_dedup_expressions_can_be_simplified_4(self):
+        l = Licensing()
+        exp = "(gpl AND mit) AND (mit AND gpl) AND (gpl OR mit)"
+        result = l.dedup(exp)
+        expected = l.parse("gpl AND mit AND (gpl OR mit)")
+        assert result == expected
+
     def test_dedup_expressions_multiple_occurrences(self):
         l = Licensing()
         exp = " GPL-2.0 or (mit and LGPL-2.1) or bsd Or GPL-2.0  or (mit and LGPL-2.1)"