Add tests and simplify comments

Signed-off-by: Ayan Sinha Mahapatra <asmahapatra@aboutcode.org>

Author: AyanSinhaMahapatra

src/license_expression/__init__.py

@@ -716,8 +716,12 @@ def dedup(self, expression):
 
         The deduplication:
 
+        - Performs the deduplication recusively for all sub-expressions.
+
         - Does not sort the licenses of sub-expression in an expression. They
-          stay in the same order as in the original expression.
+          stay in the same order as in the original expression. In case of two
+          similar expressions joined by AND, sorted differently, the sort order
+          of the first expression is retained.
 
         - Choices (as in "MIT or GPL") are kept as-is and not treated as
           simplifiable. This avoids droping important choice options in complex
@@ -751,8 +755,6 @@ def dedup(self, expression):
         ):
             relation = exp.__class__.__name__
             # 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:

tests/test_license_expression.py

@@ -735,6 +735,20 @@ def test_dedup_expressions_logically_equivalent_4(self):
         expected = l.parse("gpl AND mit")
         assert result == expected
 
+    def test_dedup_expressions_logically_equivalent_5(self):
+        l = Licensing()
+        exp = "(gpl OR mit) AND (mit OR gpl) AND ((gpl OR mit) AND (mit OR gpl))"
+        result = l.dedup(exp)
+        expected = l.parse("gpl OR mit")
+        assert result == expected
+
+    def test_dedup_expressions_logically_equivalent_6(self):
+        l = Licensing()
+        exp = "(gpl OR mit) AND (mit OR gpl) AND ((gpl OR mit) OR (mit OR gpl))"
+        result = l.dedup(exp)
+        expected = l.parse("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)"