Fix Dependency.to_pep508() for inequality specifiers

poetry/packages/dependency.py

@@ -144,9 +144,10 @@ class Dependency(object):
             requirement += "[{}]".format(",".join(self.extras))
 
         if isinstance(self.constraint, VersionUnion):
-            requirement += " ({})".format(
-                ",".join([str(c).replace(" ", "") for c in self.constraint.ranges])
-            )
+            if self.constraint.excludes_single_version():
+                requirement += " ({})".format(str(self.constraint))
+            else:
+                requirement += " ({})".format(self.pretty_constraint)
         elif isinstance(self.constraint, Version):
             requirement += " (=={})".format(self.constraint.text)
         elif not self.constraint.is_any():

poetry/semver/version_union.py

@@ -228,7 +228,7 @@ class VersionUnion(VersionConstraint):
 
         raise ValueError("Unknown VersionConstraint type {}".format(constraint))
 
-    def _excludes_single_version(self):  # type: () -> bool
+    def excludes_single_version(self):  # type: () -> bool
         from .version import Version
         from .version_range import VersionRange
 
@@ -243,7 +243,7 @@ class VersionUnion(VersionConstraint):
     def __str__(self):
         from .version_range import VersionRange
 
-        if self._excludes_single_version():
+        if self.excludes_single_version():
             return "!={}".format(VersionRange().difference(self))
 
         return " || ".join([str(r) for r in self._ranges])

tests/packages/test_dependency.py

@@ -102,3 +102,9 @@ def test_to_pep_508_in_extras():
         ") "
         'and (extra == "foo" or extra == "bar")'
     )
+
+
+def test_to_pep_508_with_single_version_excluded():
+    dependency = Dependency("foo", "!=1.2.3")
+
+    assert "foo (!=1.2.3)" == dependency.to_pep_508()