From 0e7e8208281670d36df937fc6bd42c4cea165b3b Mon Sep 17 00:00:00 2001
From: Joseph Kahn <josephbkahn@gmail.com>
Date: Thu, 28 Nov 2019 18:07:37 -0500
Subject: [PATCH] do not write empty or any markers

---
 poetry/version/markers.py     | 10 ++++++++-
 tests/version/test_markers.py | 40 +++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/poetry/version/markers.py b/poetry/version/markers.py
index 28b0bb74861..f8437348c05 100644
--- a/poetry/version/markers.py
+++ b/poetry/version/markers.py
@@ -628,7 +628,15 @@ def __hash__(self):
         return h
 
     def __str__(self):
-        return " or ".join(str(m) for m in self._markers)
+        return " or ".join(
+            str(m) for m in self._markers if not m.is_any() and not m.is_empty()
+        )
+
+    def is_any(self):
+        return all(m.is_any() for m in self._markers)
+
+    def is_empty(self):
+        return all(m.is_empty() for m in self._markers)
 
 
 def parse_marker(marker):
diff --git a/tests/version/test_markers.py b/tests/version/test_markers.py
index 382890e2e06..edd6e174f9d 100644
--- a/tests/version/test_markers.py
+++ b/tests/version/test_markers.py
@@ -354,6 +354,46 @@ def test_marker_union_union_duplicates():
     )
 
 
+def test_marker_union_all_any():
+    union = MarkerUnion(parse_marker(""), parse_marker(""))
+
+    assert union.is_any()
+
+
+def test_marker_union_not_all_any():
+    union = MarkerUnion(parse_marker(""), parse_marker(""), parse_marker("<empty>"))
+
+    assert not union.is_any()
+
+
+def test_marker_union_all_empty():
+    union = MarkerUnion(parse_marker("<empty>"), parse_marker("<empty>"))
+
+    assert union.is_empty()
+
+
+def test_marker_union_not_all_empty():
+    union = MarkerUnion(
+        parse_marker("<empty>"), parse_marker("<empty>"), parse_marker("")
+    )
+
+    assert not union.is_empty()
+
+
+def test_marker_str_conversion_skips_empty_and_any():
+    union = MarkerUnion(
+        parse_marker("<empty>"),
+        parse_marker(
+            'sys_platform == "darwin" or python_version <= "3.6" or os_name == "Windows"'
+        ),
+        parse_marker(""),
+    )
+
+    assert str(union) == (
+        'sys_platform == "darwin" or python_version <= "3.6" or os_name == "Windows"'
+    )
+
+
 def test_intersect_compacts_constraints():
     m = parse_marker('python_version < "4.0"')