Always re-solve directory dependencies

src/poetry/installation/installer.py

@@ -201,10 +201,16 @@ def _do_refresh(self) -> int:
             self._io,
         )
 
+        # Always re-solve directory dependencies, otherwise we can't determine
+        # if anything has changed (and the lock file contains an invalid version).
+        use_latest = [
+            p.name for p in locked_repository.packages if p.source_type == "directory"
+        ]
+
         with solver.provider.use_source_root(
             source_root=self._env.path.joinpath("src")
         ):
-            ops = solver.solve(use_latest=[]).calculate_operations()
+            ops = solver.solve(use_latest=use_latest).calculate_operations()
 
         lockfile_repo = LockfileRepository()
         self._populate_lockfile_repo(lockfile_repo, ops)

tests/console/commands/test_lock.py

@@ -43,6 +43,7 @@ def _project_factory(
         name="foobar",
         pyproject_content=pyproject_content,
         poetry_lock_content=poetry_lock_content,
+        source=source,
     )
 
 
@@ -67,6 +68,13 @@ def poetry_with_old_lockfile(
     return _project_factory("old_lock", project_factory, fixture_dir)
 
 
+@pytest.fixture
+def poetry_with_nested_path_deps_old_lockfile(
+    project_factory: ProjectFactory, fixture_dir: FixtureDirGetter
+) -> Poetry:
+    return _project_factory("old_lock_path_dependency", project_factory, fixture_dir)
+
+
 @pytest.fixture
 def poetry_with_incompatible_lockfile(
     project_factory: ProjectFactory, fixture_dir: FixtureDirGetter
@@ -166,6 +174,36 @@ def test_lock_no_update(
         assert locked_repository.find_packages(package.to_dependency())
 
 
+def test_lock_no_update_path_dependencies(
+    command_tester_factory: CommandTesterFactory,
+    poetry_with_nested_path_deps_old_lockfile: Poetry,
+    repo: TestRepository,
+):
+    """
+    The lock file contains a variant of the directory dependency "quix" that does
+    not depend on "sampleproject". Although the version of "quix" has not been changed,
+    it should be re-solved because there is always only one valid version
+    of a directory dependency at any time.
+    """
+    repo.add_package(get_package("sampleproject", "1.3.1"))
+
+    locker = Locker(
+        lock=poetry_with_nested_path_deps_old_lockfile.pyproject.file.path.parent
+        / "poetry.lock",
+        local_config=poetry_with_nested_path_deps_old_lockfile.locker._local_config,
+    )
+    poetry_with_nested_path_deps_old_lockfile.set_locker(locker)
+
+    tester = command_tester_factory(
+        "lock", poetry=poetry_with_nested_path_deps_old_lockfile
+    )
+    tester.execute("--no-update")
+
+    packages = locker.locked_repository().packages
+
+    assert {p.name for p in packages} == {"quix", "sampleproject"}
+
+
 @pytest.mark.parametrize("is_no_update", [False, True])
 def test_lock_with_incompatible_lockfile(
     command_tester_factory: CommandTesterFactory,

tests/fixtures/old_lock_path_dependency/pyproject.toml

@@ -0,0 +1,15 @@
+[tool.poetry]
+name = "foobar"
+version = "0.1.0"
+description = ""
+authors = ["Poetry Developer <developer@python-poetry.org>"]
+
+[tool.poetry.dependencies]
+python = "^3.8"
+quix = { path = "./quix", develop = true}
+
+[tool.poetry.dev-dependencies]
+
+[build-system]
+requires = ["poetry-core>=1.0.0"]
+build-backend = "poetry.core.masonry.api"

tests/fixtures/old_lock_path_dependency/quix/pyproject.toml

@@ -0,0 +1,11 @@
+[tool.poetry]
+name = "quix"
+version = "1.2.3"
+description = "Some description."
+authors = ["Poetry Maintainer <tests@python-poetry.org>"]
+license = "MIT"
+
+# Requirements
+[tool.poetry.dependencies]
+python = "~2.7 || ^3.4"
+sampleproject = ">=1.3.1"