avoid infinite loop when adding a dependency (#7405)

src/poetry/mixology/version_solver.py

@@ -331,7 +331,9 @@ def _resolve_conflict(self, incompatibility: Incompatibility) -> Incompatibility
             # .. _algorithm documentation:
             # https://github.com/dart-lang/pub/tree/master/doc/solver.md#conflict-resolution  # noqa: E501
             if difference is not None:
-                new_terms.append(difference.inverse)
+                inverse = difference.inverse
+                if inverse.dependency != most_recent_satisfier.dependency:
+                    new_terms.append(inverse)
 
             incompatibility = Incompatibility(
                 new_terms, ConflictCause(incompatibility, most_recent_satisfier.cause)

tests/conftest.py

@@ -378,6 +378,7 @@ def _factory(
         install_deps: bool = True,
         source: Path | None = None,
         locker_config: dict[str, Any] | None = None,
+        use_test_locker: bool = True,
     ) -> Poetry:
         project_dir = workspace / f"poetry-fixture-{name}"
         dependencies = dependencies or {}
@@ -412,12 +413,14 @@ def _factory(
 
         poetry = Factory().create_poetry(project_dir)
 
-        locker = TestLocker(
-            poetry.locker.lock, locker_config or poetry.locker._local_config
-        )
-        locker.write()
+        if use_test_locker:
+            locker = TestLocker(
+                poetry.locker.lock, locker_config or poetry.locker._local_config
+            )
+            locker.write()
+
+            poetry.set_locker(locker)
 
-        poetry.set_locker(locker)
         poetry.set_config(config)
 
         pool = RepositoryPool()

tests/console/commands/test_add.py

@@ -10,6 +10,7 @@
 from poetry.core.constraints.version import Version
 from poetry.core.packages.package import Package
 
+from poetry.puzzle.exceptions import SolverProblemError
 from poetry.repositories.legacy_repository import LegacyRepository
 from tests.helpers import get_dependency
 from tests.helpers import get_package
@@ -45,6 +46,20 @@ def poetry_with_up_to_date_lockfile(
     )
 
 
+@pytest.fixture
+def poetry_with_path_dependency(
+    project_factory: ProjectFactory, fixture_dir: FixtureDirGetter
+) -> Poetry:
+    source = fixture_dir("with_path_dependency")
+
+    poetry = project_factory(
+        name="foobar",
+        source=source,
+        use_test_locker=False,
+    )
+    return poetry
+
+
 @pytest.fixture()
 def tester(command_tester_factory: CommandTesterFactory) -> CommandTester:
     return command_tester_factory("add")
@@ -2238,3 +2253,21 @@ def error(_: Any) -> int:
     assert poetry_with_up_to_date_lockfile.file.read() == original_pyproject_content
     assert poetry_with_up_to_date_lockfile.locker.lock_data == original_lockfile_content
     assert tester.io.fetch_output() == expected
+
+
+def test_add_with_path_dependency_no_loopiness(
+    poetry_with_path_dependency: Poetry,
+    repo: TestRepository,
+    command_tester_factory: CommandTesterFactory,
+) -> None:
+    """https://github.com/python-poetry/poetry/issues/7398"""
+    tester = command_tester_factory("add", poetry=poetry_with_path_dependency)
+
+    requests_old = get_package("requests", "2.25.1")
+    requests_new = get_package("requests", "2.28.2")
+
+    repo.add_package(requests_old)
+    repo.add_package(requests_new)
+
+    with pytest.raises(SolverProblemError):
+        tester.execute("requests")

tests/fixtures/with_path_dependency/bazz/setup.py

@@ -0,0 +1,12 @@
+from __future__ import annotations
+
+from distutils.core import setup
+
+
+setup(
+    name="bazz",
+    version="1",
+    py_modules=["demo"],
+    package_dir={"src": "src"},
+    install_requires=["requests~=2.25.1"],
+)

tests/fixtures/with_path_dependency/pyproject.toml

@@ -0,0 +1,15 @@
+[tool.poetry]
+name = "foobar"
+version = "0.1.0"
+description = ""
+authors = []
+readme = "README.md"
+packages = [{include = "foobar"}]
+
+[tool.poetry.dependencies]
+python = "^3.9"
+bazz = { path = "./bazz", develop = true }
+
+[build-system]
+requires = ["poetry-core"]
+build-backend = "poetry.core.masonry.api"

tests/types.py

@@ -46,6 +46,7 @@ def __call__(
         poetry_lock_content: str | None = None,
         install_deps: bool = True,
         source: Path | None = None,
+        use_test_locker: bool = True,
     ) -> Poetry:
         ...