Add function to invert constraints and ranges #91

CHANGELOG.rst

@@ -2,6 +2,12 @@ Changelog
 =========
 
 
+Version v30.9.1
+----------------
+
+- Add invert function to VersionRange.
+
+
 Version v30.9.0
 ----------------
 

src/univers/version_constraint.py

@@ -132,6 +132,28 @@ def __lt__(self, other):
         # we compare tuples, version first
         return (self.version, self.comparator).__lt__((other.version, other.comparator))
 
+    def is_star(self):
+        return self.comparator == "*"
+
+    def invert(self):
+        INVERTED_COMPARATORS = {
+            ">=": "<",
+            "<=": ">",
+            "!=": "=",
+            "<": ">=",
+            ">": "<=",
+            "=": "!=",
+        }
+
+        if self.is_star():
+            return None
+
+        inverted_comparator = INVERTED_COMPARATORS[self.comparator]
+        return self.__class__(
+            comparator=inverted_comparator,
+            version=self.version,
+        )
+
     @classmethod
     def from_string(cls, string, version_class):
         """

src/univers/version_range.py

@@ -25,6 +25,16 @@ class InvalidVersionRange(Exception):
     """
 
 
+INVERTED_COMPARATORS = {
+    ">=": "<",
+    "<=": ">",
+    "!=": "=",
+    "<": ">=",
+    ">": "<=",
+    "=": "!=",
+}
+
+
 @attr.s(frozen=True, order=False, eq=True, hash=True)
 class VersionRange:
     """
@@ -164,6 +174,27 @@ def from_versions(cls, sequence):
             constraints.append(constraint)
         return cls(constraints=constraints)
 
+    def is_star(self):
+        return len(self.constraints) == 1 and self.constraints[0].is_star()
+
+    def invert(self):
+        """
+        Return the inverse or complement of this VersionRange. For example, if this range is
+        ">=1.0.0", the inverse is "<1.0.0".
+        >>> str(VersionRange.from_string("vers:npm/>=1.0.0").invert())
+        'vers:npm/<1.0.0'
+        """
+        inverted_constraints = []
+
+        if self.is_star():
+            # The inverse of "*" is an empty range.
+            return None
+
+        for constraint in self.constraints:
+            inverted_constraints.append(constraint.invert())
+
+        return self.__class__(constraints=inverted_constraints)
+
     def __str__(self):
         constraints = "|".join(str(c) for c in sorted(self.constraints))
         return f"vers:{self.scheme}/{constraints}"

tests/test_version_range.py

@@ -393,3 +393,20 @@ def test_npm_advisory_version_range_parse(test_case):
         string=test_case["npm_native"],
     )
     assert str(result) == test_case["expected_vers"]
+
+
+def test_inverse():
+    vers_with_equal_operator = VersionRange.from_string("vers:gem/1.0")
+    assert str(vers_with_equal_operator.invert()) == "vers:gem/!=1.0"
+    assert VersionRange.from_string("vers:gem/!=1.0").invert() == vers_with_equal_operator
+
+    vers_with_less_than_operator = VersionRange.from_string("vers:gem/<1.0")
+    assert str(vers_with_less_than_operator.invert()) == "vers:gem/>=1.0"
+    assert VersionRange.from_string("vers:gem/>=1.0").invert() == vers_with_less_than_operator
+
+    vers_with_greater_than_operator = VersionRange.from_string("vers:gem/>1.0")
+    assert str(vers_with_greater_than_operator.invert()) == "vers:gem/<=1.0"
+    assert VersionRange.from_string("vers:gem/<=1.0").invert() == vers_with_greater_than_operator
+
+    vers_with_complex_constraints = VersionRange.from_string("vers:gem/<=1.0|>=3.0|<4.0|!=5.0")
+    assert str(vers_with_complex_constraints.invert()) == "vers:gem/>1.0|<3.0|>=4.0|5.0"