From 6e823619d94c268a71469c8257493d39ef20c7bc Mon Sep 17 00:00:00 2001
From: David Hotham <david.hotham@microsoft.com>
Date: Fri, 4 Feb 2022 01:12:45 +0000
Subject: [PATCH 1/2] A multimarker with one marker is just that marker

---
 src/poetry/core/version/markers.py |  4 ++--
 tests/version/test_markers.py      | 11 ++++++++---
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/poetry/core/version/markers.py b/src/poetry/core/version/markers.py
index 7b2e98627..ed545e6a8 100644
--- a/src/poetry/core/version/markers.py
+++ b/src/poetry/core/version/markers.py
@@ -449,8 +449,8 @@ def of(cls, *markers: MarkerTypes) -> MarkerTypes:
         if any(m.is_empty() for m in new_markers) or not new_markers:
             return EmptyMarker()
 
-        if len(new_markers) == 1 and new_markers[0].is_any():
-            return AnyMarker()
+        if len(new_markers) == 1:
+            return new_markers[0]
 
         return MultiMarker(*new_markers)
 
diff --git a/tests/version/test_markers.py b/tests/version/test_markers.py
index 408501284..8f67234a4 100644
--- a/tests/version/test_markers.py
+++ b/tests/version/test_markers.py
@@ -685,13 +685,13 @@ def test_without_extras(marker: str, expected: str):
         (
             'python_version >= "3.6" and (extra == "foo" or extra == "bar")',
             "python_version",
-            '(extra == "foo" or extra == "bar")',
+            'extra == "foo" or extra == "bar"',
         ),
         (
             'python_version >= "3.6" and (extra == "foo" or extra == "bar") or'
             ' implementation_name == "pypy"',
             "python_version",
-            '(extra == "foo" or extra == "bar") or implementation_name == "pypy"',
+            'extra == "foo" or extra == "bar" or implementation_name == "pypy"',
         ),
         (
             'python_version >= "3.6" and extra == "foo" or implementation_name =='
@@ -705,6 +705,11 @@ def test_without_extras(marker: str, expected: str):
             "implementation_name",
             'python_version >= "3.6" or extra == "foo" or extra == "bar"',
         ),
+        (
+            'extra == "foo" and python_version >= "3.6" or python_version >= "3.6"',
+            "extra",
+            'python_version >= "3.6"',
+        ),
     ],
 )
 def test_exclude(marker: str, excluded: str, expected: str):
@@ -728,7 +733,7 @@ def test_exclude(marker: str, excluded: str, expected: str):
         (
             'python_version >= "3.6" and (extra == "foo" or extra == "bar")',
             ["extra"],
-            '(extra == "foo" or extra == "bar")',
+            'extra == "foo" or extra == "bar"',
         ),
         (
             'python_version >= "3.6" and (extra == "foo" or extra == "bar") or'

From 9743333aaa9806b4509fb12f90d0cbe5a92d20dc Mon Sep 17 00:00:00 2001
From: David Hotham <david.hotham@microsoft.com>
Date: Fri, 4 Feb 2022 09:31:58 +0000
Subject: [PATCH 2/2] simplify obvious unions

---
 src/poetry/core/version/markers.py | 3 +++
 tests/version/test_markers.py      | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/src/poetry/core/version/markers.py b/src/poetry/core/version/markers.py
index ed545e6a8..e12e880ac 100644
--- a/src/poetry/core/version/markers.py
+++ b/src/poetry/core/version/markers.py
@@ -470,6 +470,9 @@ def intersect(self, other: MarkerTypes) -> MarkerTypes:
         return MultiMarker.of(*new_markers)
 
     def union(self, other: MarkerTypes) -> MarkerTypes:
+        if other in self._markers:
+            return other
+
         if isinstance(other, (SingleMarker, MultiMarker)):
             return MarkerUnion.of(self, other)
 
diff --git a/tests/version/test_markers.py b/tests/version/test_markers.py
index 8f67234a4..b3f867206 100644
--- a/tests/version/test_markers.py
+++ b/tests/version/test_markers.py
@@ -773,6 +773,14 @@ def test_union_of_a_single_marker_is_the_single_marker():
     assert SingleMarker("python_version", ">= 2.7") == union
 
 
+def test_union_of_multi_with_a_containing_single():
+    single = parse_marker('python_version >= "2.7"')
+    multi = parse_marker('python_version >= "2.7" and extra == "foo"')
+    union = multi.union(single)
+
+    assert union == single
+
+
 @pytest.mark.parametrize(
     "marker, inverse",
     [