Fix propagation of include_prerelease when calculating VersionRange intersection

conans/model/version_range.py

@@ -140,6 +140,14 @@ def valid(self, version, conf_resolve_prepreleases):
                     return False
         return True
 
+    def __eq__(self, other):
+        if not isinstance(other, _ConditionSet):
+            return False
+        if len(self.conditions) !=  len(other.conditions):
+            return False
+        return (self.prerelease == other.prerelease
+                and all(c == o for c, o in zip(self.conditions, other.conditions)))
+
 
 class VersionRange:
     def __init__(self, expression):
@@ -187,6 +195,10 @@ def contains(self, version: Version, resolve_prerelease: Optional[bool]):
         return False
 
     def intersection(self, other):
+        # skip calculations if ranges are equal
+        if self.condition_sets == other.condition_sets:
+            return VersionRange(self._expression)
+
         conditions = []
 
         def _calculate_limits(operator, lhs, rhs):
@@ -195,6 +207,7 @@ def _calculate_limits(operator, lhs, rhs):
             if limits:
                 return sorted(limits, reverse=operator == ">")[0]
 
+        prerelease = True
         for lhs_conditions in self.condition_sets:
             for rhs_conditions in other.condition_sets:
                 internal_conditions = []
@@ -206,10 +219,13 @@ def _calculate_limits(operator, lhs, rhs):
                     internal_conditions.append(upper_limit)
                 if internal_conditions and (not lower_limit or not upper_limit or lower_limit <= upper_limit):
                     conditions.append(internal_conditions)
+                # conservative approach: if any of the conditions forbid prereleases, forbid them in the result
+                if not lhs_conditions.prerelease or not rhs_conditions.prerelease:
+                    prerelease = False
 
         if not conditions:
             return None
-        expression = ' || '.join(' '.join(str(c) for c in cs) for cs in conditions)
+        expression = ' || '.join(' '.join(str(c) for c in cs) for cs in conditions) + (', include_prerelease' if prerelease else '')
         result = VersionRange(expression)
         # TODO: Direct definition of conditions not reparsing
         # result.condition_sets = self.condition_sets + other.condition_sets

test/unittests/model/version/test_version_range_intersection.py

@@ -80,3 +80,51 @@ def test_range_intersection_incompatible(range1, range2):
     assert inter is None
     inter = r2.intersection(r1)  # Test reverse order, result should be the same
     assert inter is None
+
+
+prerelease_values = [
+    [">=1.0-pre.1 <1.0-pre.99, include_prerelease",
+     ">=1.0-pre.1 <1.0-pre.99, include_prerelease",
+     ">=1.0-pre.1 <1.0-pre.99, include_prerelease"],
+    [">=1.0-pre.1 <1.0-pre.99, include_prerelease",
+     ">=1.0-pre.12 <1.0-pre.98, include_prerelease",
+     ">=1.0-pre.12 <1.0-pre.98, include_prerelease"],
+    [">=1.0-pre.12 <1.0-pre.99, include_prerelease",
+     ">=1.0-pre.1 <1.0-pre.98, include_prerelease",
+     ">=1.0-pre.12 <1.0-pre.98, include_prerelease"],
+    [">=1.0-pre.1 <1.0-pre.99",
+     ">=1.0-pre.1 <1.0-pre.99, include_prerelease",
+     ">=1.0-pre.1 <1.0-pre.99"],
+    [">=1.0-pre.1 <1.0-pre.99, include_prerelease",
+     ">=1.0-pre.12 <1.0-pre.98",
+     ">=1.0-pre.12 <1.0-pre.98"],
+    [">=1.0-pre.12 <1.0-pre.99",
+     ">=1.0-pre.1 <1.0-pre.98",
+     ">=1.0-pre.12 <1.0-pre.98"]
+]
+
+
+@pytest.mark.parametrize("range1, range2, result", prerelease_values)
+def test_range_intersection_prerelease(range1, range2, result):
+    r1 = VersionRange(range1)
+    r2 = VersionRange(range2)
+    inter = r1.intersection(r2)
+    assert str(inter.version()) == f'[{result}]'
+    inter = r2.intersection(r1)  # Test reverse order, result should be the same
+    assert str(inter.version()) == f'[{result}]'
+
+
+@pytest.mark.parametrize("range1, range2, result", [
+    [">=1.0,include_prerelease", ">=1.0, include_prerelease", ">=1.0,include_prerelease"],
+    [">=1.0, include_prerelease", ">=1.0,include_prerelease", ">=1.0, include_prerelease"],
+    [">=1.0,include_prerelease", ">=1.0", ">=1.0"],
+    [">=1.0", ">=1.0,include_prerelease", ">=1.0"],
+])
+def test_version_range_intersection_shortcircuit(range1, range2, result):
+    r1 = VersionRange(range1)
+    r2 = VersionRange(range2)
+    inter = r1.intersection(r2)
+    # Same expression as first one
+    assert inter._expression == result
+    # But make sure we don't actually just return the first object itself, reevaluate it always!
+    assert r1 is not inter