reject empty python versions (#761)

src/poetry/core/packages/package.py

@@ -278,6 +278,9 @@ def python_versions(self, value: str) -> None:
  except ParseConstraintError:
  raise ParseConstraintError(f"Invalid python versions '{value}' on {self}")
 
+ if constraint.is_empty():
+ raise ParseConstraintError(f"Python versions '{value}' on {self} is empty")
+
  self._python_versions = value
  self._python_constraint = constraint
  self._python_marker = parse_marker(

src/poetry/core/packages/utils/utils.py

@@ -239,7 +239,9 @@ def create_nested_marker(
 
  marker = f'{name} == "{constraint.text}"'
  else:
- assert isinstance(constraint, VersionRange)
+ assert isinstance(
+ constraint, VersionRange
+ ), f"Unexpected constraint of type {type(constraint)}"
  min_name = max_name = name
 
  parts = []

tests/packages/test_package.py

@@ -658,3 +658,12 @@ def test_package_invalid_python_versions() -> None:
 
  expected = "Invalid python versions '>=3.6.y' on foo (1.2.3)"
  assert str(exc_info.value) == expected
+
+
+def test_package_empty_python_versions() -> None:
+ package = Package("foo", "1.2.3")
+ with pytest.raises(ParseConstraintError) as exc_info:
+ package.python_versions = "~2.7, >=3.4, <3.8"
+
+ expected = "Python versions '~2.7, >=3.4, <3.8' on foo (1.2.3) is empty"
+ assert str(exc_info.value) == expected