Fix incorrect package being selected with transitive markers.

poetry/mixology/version_solver.py

@@ -4,6 +4,7 @@
 from typing import Dict
 from typing import List
 from typing import Optional
+from typing import Tuple
 from typing import Union
 
 from poetry.core.packages.dependency import Dependency
@@ -327,19 +328,19 @@ def _choose_package_version(self) -> Optional[str]:
 
         # Prefer packages with as few remaining versions as possible,
         # so that if a conflict is necessary it's forced quickly.
-        def _get_min(dependency: Dependency) -> int:
+        def _get_min(dependency: Dependency) -> Tuple[bool, int]:
             if dependency.name in self._use_latest:
                 # If we're forced to use the latest version of a package, it effectively
                 # only has one version to choose from.
-                return 1
+                return not dependency.marker.is_any(), 1
 
             locked = self._get_locked(dependency)
             if locked and (
                 dependency.constraint.allows(locked.version)
                 or locked.is_prerelease()
                 and dependency.constraint.allows(locked.version.next_patch())
             ):
-                return 1
+                return not dependency.marker.is_any(), 1
 
             # VCS, URL, File or Directory dependencies
             # represent a single version
@@ -349,12 +350,15 @@ def _get_min(dependency: Dependency) -> int:
                 or dependency.is_file()
                 or dependency.is_directory()
             ):
-                return 1
+                return not dependency.marker.is_any(), 1
 
             try:
-                return len(self._provider.search_for(dependency))
+                return (
+                    not dependency.marker.is_any(),
+                    len(self._provider.search_for(dependency)),
+                )
             except ValueError:
-                return 0
+                return not dependency.marker.is_any(), 0
 
         if len(unsatisfied) == 1:
             dependency = unsatisfied[0]

tests/puzzle/test_solver.py

@@ -2791,3 +2791,53 @@ def test_solver_can_resolve_python_restricted_package_dependencies(
             {"job": "install", "package": pre_commit},
         ],
     )
+
+
+def test_solver_should_not_raise_errors_for_irrelevant_transitive_python_constraints(
+    solver, repo, package
+):
+    package.python_versions = "~2.7 || ^3.5"
+    solver.provider.set_package_python_versions("~2.7 || ^3.5")
+    package.add_dependency(Factory.create_dependency("virtualenv", "^20.4.3"))
+    package.add_dependency(
+        Factory.create_dependency("pre-commit", {"version": "^2.6", "python": "^3.6.1"})
+    )
+
+    virtualenv = get_package("virtualenv", "20.4.3")
+    virtualenv.python_versions = "!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,>=2.7"
+    virtualenv.add_dependency(
+        Factory.create_dependency(
+            "importlib-resources", {"version": "*", "markers": 'python_version < "3.7"'}
+        )
+    )
+
+    pre_commit = Package("pre-commit", "2.7.1")
+    pre_commit.python_versions = ">=3.6.1"
+    pre_commit.add_dependency(
+        Factory.create_dependency(
+            "importlib-resources", {"version": "*", "markers": 'python_version < "3.7"'}
+        )
+    )
+
+    importlib_resources = get_package("importlib-resources", "5.1.2")
+    importlib_resources.python_versions = ">=3.6"
+
+    importlib_resources_3_2_1 = get_package("importlib-resources", "3.2.1")
+    importlib_resources_3_2_1.python_versions = (
+        "!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*,!=3.4.*,>=2.7"
+    )
+
+    repo.add_package(virtualenv)
+    repo.add_package(pre_commit)
+    repo.add_package(importlib_resources)
+    repo.add_package(importlib_resources_3_2_1)
+    ops = solver.solve()
+
+    check_solver_result(
+        ops,
+        [
+            {"job": "install", "package": importlib_resources_3_2_1},
+            {"job": "install", "package": pre_commit},
+            {"job": "install", "package": virtualenv},
+        ],
+    )