Ignore combinations of overrides whose intersection of markers is empty

src/poetry/puzzle/provider.py

@@ -16,8 +16,10 @@ from typing import Iterator
 
 from cleo.ui.progress_indicator import ProgressIndicator
 from poetry.core.packages.utils.utils import get_python_constraint_from_marker
+from poetry.core.semver.empty_constraint import EmptyConstraint
 from poetry.core.semver.version import Version
 from poetry.core.vcs.git import Git
+from poetry.core.version.markers import AnyMarker
 from poetry.core.version.markers import MarkerUnion
 
 from poetry.inspection.info import PackageInfo
@@ -69,7 +71,7 @@ class Provider:
         self._python_constraint = package.python_constraint
         self._is_debugging = self._io.is_debug() or self._io.is_very_verbose()
         self._in_progress = False
-        self._overrides: dict = {}
+        self._overrides: dict[DependencyPackage, dict[str, Dependency]] = {}
         self._deferred_cache: dict[Dependency, Package] = {}
         self._load_deferred = True
 
@@ -331,6 +333,28 @@ class Provider:
 
         return package
 
+    def _get_dependencies_with_overrides(
+        self, dependencies: list[Dependency], package: DependencyPackage
+    ) -> list[Dependency]:
+        overrides = self._overrides.get(package, {})
+        _dependencies = []
+        overridden = []
+        for dep in dependencies:
+            if dep.name in overrides:
+                if dep.name in overridden:
+                    continue
+
+                # empty constraint is used in overrides to mark that the package has
+                # already been handled and is not required for the attached markers
+                if not overrides[dep.name].constraint.is_empty():
+                    _dependencies.append(overrides[dep.name])
+                overridden.append(dep.name)
+
+                continue
+
+            _dependencies.append(dep)
+        return _dependencies
+
     def incompatibilities_for(
         self, package: DependencyPackage
     ) -> list[Incompatibility]:
@@ -384,21 +408,7 @@ class Provider:
             and self._python_constraint.allows_any(dep.python_constraint)
             and (not self._env or dep.marker.validate(self._env.marker_env))
         ]
-
-        overrides = self._overrides.get(package, {})
-        dependencies = []
-        overridden = []
-        for dep in _dependencies:
-            if dep.name in overrides:
-                if dep.name in overridden:
-                    continue
-
-                dependencies.append(overrides[dep.name])
-                overridden.append(dep.name)
-
-                continue
-
-            dependencies.append(dep)
+        dependencies = self._get_dependencies_with_overrides(_dependencies, package)
 
         return [
             Incompatibility(
@@ -480,20 +490,7 @@ class Provider:
 
             _dependencies.append(dep)
 
-        overrides = self._overrides.get(package, {})
-        dependencies = []
-        overridden = []
-        for dep in _dependencies:
-            if dep.name in overrides:
-                if dep.name in overridden:
-                    continue
-
-                dependencies.append(overrides[dep.name])
-                overridden.append(dep.name)
-
-                continue
-
-            dependencies.append(dep)
+        dependencies = self._get_dependencies_with_overrides(_dependencies, package)
 
         # Searching for duplicate dependencies
         #
@@ -629,27 +626,48 @@ class Provider:
             any_markers_dependencies = [d for d in _deps if d.marker.is_any()]
             other_markers_dependencies = [d for d in _deps if not d.marker.is_any()]
 
-            if any_markers_dependencies:
             marker = other_markers_dependencies[0].marker
             for other_dep in other_markers_dependencies[1:]:
                 marker = marker.union(other_dep.marker)
-
             inverted_marker = marker.invert()
+
+            if any_markers_dependencies:
                 for dep_any in any_markers_dependencies:
                     dep_any.marker = inverted_marker
                     for dep_other in other_markers_dependencies:
                         dep_other.set_constraint(
                             dep_other.constraint.intersect(dep_any.constraint)
                         )
+            else:
+                # if there is no any marker dependency,
+                # a dependency with the inverted union of all markers is required
+                # in order to not miss other dependencies later, for instance:
+                #   - foo (1.0) ; python == 3.7
+                #   - foo (2.0) ; python == 3.8
+                #   - bar (2.0) ; python == 3.8
+                #   - bar (3.0) ; python == 3.9
+                #
+                # the last dependency would be missed without this,
+                # because the intersection with both foo dependencies is empty
+                inverted_marker_dep = _deps[0].with_constraint(EmptyConstraint())
+                inverted_marker_dep.marker = inverted_marker
+                _deps.append(inverted_marker_dep)
 
             overrides = []
+            overrides_marker_intersection = AnyMarker()
+            for _dep in self._overrides.get(package, {}).values():
+                overrides_marker_intersection = overrides_marker_intersection.intersect(
+                    _dep.marker
+                )
             for _dep in _deps:
+                if not overrides_marker_intersection.intersect(_dep.marker).is_empty():
                     current_overrides = self._overrides.copy()
                     package_overrides = current_overrides.get(package, {}).copy()
                     package_overrides.update({_dep.name: _dep})
                     current_overrides.update({package: package_overrides})
                     overrides.append(current_overrides)
 
+            if overrides:
                 raise OverrideNeeded(*overrides)
 
         # Modifying dependencies as needed

tests/puzzle/test_solver.py

@@ -1343,6 +1343,77 @@ def test_solver_duplicate_dependencies_different_constraints_merge_no_markers(
     )
 
 
+def test_solver_duplicate_dependencies_ignore_overrides_with_empty_marker_intersection(
+    solver: Solver, repo: Repository, package: Package
+):
+    """
+    Distinct requirements per marker:
+    * Python 2.7: A (which requires B) and B
+    * Python 3.6: same as Python 2.7 but with different versions
+    * Python 3.7: only A
+    * Python 3.8: only B
+    """
+    package.add_dependency(
+        Factory.create_dependency("A", {"version": "1.0", "python": "~2.7"})
+    )
+    package.add_dependency(
+        Factory.create_dependency("A", {"version": "2.0", "python": "~3.6"})
+    )
+    package.add_dependency(
+        Factory.create_dependency("A", {"version": "3.0", "python": "~3.7"})
+    )
+    package.add_dependency(
+        Factory.create_dependency("B", {"version": "1.0", "python": "~2.7"})
+    )
+    package.add_dependency(
+        Factory.create_dependency("B", {"version": "2.0", "python": "~3.6"})
+    )
+    package.add_dependency(
+        Factory.create_dependency("B", {"version": "3.0", "python": "~3.8"})
+    )
+
+    package_a10 = get_package("A", "1.0")
+    package_a10.add_dependency(
+        Factory.create_dependency("B", {"version": "^1.0", "python": "~2.7"})
+    )
+
+    package_a20 = get_package("A", "2.0")
+    package_a20.add_dependency(
+        Factory.create_dependency("B", {"version": "^2.0", "python": "~3.6"})
+    )
+
+    package_a30 = get_package("A", "3.0")  # no dep to B
+
+    package_b10 = get_package("B", "1.0")
+    package_b11 = get_package("B", "1.1")
+    package_b20 = get_package("B", "2.0")
+    package_b21 = get_package("B", "2.1")
+    package_b30 = get_package("B", "3.0")
+
+    repo.add_package(package_a10)
+    repo.add_package(package_a20)
+    repo.add_package(package_a30)
+    repo.add_package(package_b10)
+    repo.add_package(package_b11)
+    repo.add_package(package_b20)
+    repo.add_package(package_b21)
+    repo.add_package(package_b30)
+
+    transaction = solver.solve()
+
+    check_solver_result(
+        transaction,
+        [
+            {"job": "install", "package": package_b10},
+            {"job": "install", "package": package_b20},
+            {"job": "install", "package": package_a10},
+            {"job": "install", "package": package_a20},
+            {"job": "install", "package": package_a30},
+            {"job": "install", "package": package_b30},
+        ],
+    )
+
+
 def test_solver_duplicate_dependencies_sub_dependencies(
     solver: Solver, repo: Repository, package: ProjectPackage
 ):