Fix the solver adding a package as a dependency of itself when extras are involved (#5769)

* Add Failing test for #5727

* Fixes #5727

Co-authored-by: Dos Moonen <d.moonen@nki.nl>

src/poetry/puzzle/solver.py

@@ -164,21 +164,20 @@ class Solver:
             if package.features:
                 for _package in packages:
                     if (
-                        _package.name == package.name
-                        and not _package.is_same_package_as(package)
+                        not _package.features
+                        and _package.name == package.name
                         and _package.version == package.version
                     ):
                         for dep in package.requires:
-                            if dep.is_same_package_as(_package):
+                            # Prevent adding base package as a dependency to itself
+                            if _package.name == dep.name:
                                 continue
 
                             if dep not in _package.requires:
                                 _package.add_dependency(dep)
-
-                continue
-
-            final_packages.append(package)
-            depths.append(results[package])
+            else:
+                final_packages.append(package)
+                depths.append(results[package])
 
         # Return the packages in their original order with associated depths
         return final_packages, depths

tests/puzzle/test_solver.py

@@ -793,6 +793,38 @@ def test_solver_finds_extras_next_to_non_extras(
     )
 
 
+def test_solver_merge_extras_into_base_package_multiple_repos_fixes_5727(
+    solver: Solver, repo: Repository, pool: Pool, package: ProjectPackage
+):
+    package.add_dependency(
+        Factory.create_dependency("A", {"version": "*", "source": "legacy"})
+    )
+    package.add_dependency(Factory.create_dependency("B", {"version": "*"}))
+
+    package_a = get_package("A", "1.0")
+    package_a.extras = {"foo": []}
+
+    repo.add_package(package_a)
+
+    package_b = Package("B", "1.0", source_type="legacy")
+    package_b.add_dependency(package_a.with_features(["foo"]).to_dependency())
+
+    package_a = Package("A", "1.0", source_type="legacy")
+    package_a.extras = {"foo": []}
+
+    repo = Repository("legacy")
+    repo.add_package(package_a)
+    repo.add_package(package_b)
+
+    pool.add_repository(repo)
+
+    transaction = solver.solve()
+
+    ops = transaction.calculate_operations(synchronize=True)
+
+    assert len(ops[0].package.requires) == 0, "a should not require itself"
+
+
 def test_solver_returns_prereleases_if_requested(
     solver: Solver, repo: Repository, package: ProjectPackage
 ):