Do not write PEP610 URL reference for cached packages installed from …

…a private source (#5362)

src/poetry/installation/executor.py

@@ -725,11 +725,11 @@ def _save_url_reference(self, operation: OperationTypes) -> None:
 
         package = operation.package
 
-        if not package.source_url:
+        if not package.source_url or package.source_type == "legacy":
             # Since we are installing from our own distribution cache
             # pip will write a `direct_url.json` file pointing to the cache
             # distribution.
-            # That's not what we want so we remove the direct_url.json file,
+            # That's not what we want, so we remove the direct_url.json file,
             # if it exists.
             for (
                 direct_url_json

tests/installation/test_executor.py

@@ -411,6 +411,42 @@ def verify_installed_distribution(
         assert not direct_url_file.exists()
 
 
+@pytest.mark.parametrize(
+    "package",
+    [
+        Package("demo", "0.1.0"),  # PyPI
+        Package(  # private source
+            "demo",
+            "0.1.0",
+            source_type="legacy",
+            source_url="http://localhost:3141/root/pypi/+simple",
+            source_reference="private",
+        ),
+    ],
+)
+def test_executor_should_not_write_pep610_url_references_for_cached_package(
+    package: Package,
+    mocker: MockerFixture,
+    fixture_dir: FixtureDirGetter,
+    tmp_venv: VirtualEnv,
+    pool: Pool,
+    config: Config,
+    io: BufferedIO,
+):
+    link_cached = Link(
+        fixture_dir("distributions")
+        .joinpath("demo-0.1.0-py2.py3-none-any.whl")
+        .as_uri()
+    )
+    mocker.patch(
+        "poetry.installation.executor.Executor._download", return_value=link_cached
+    )
+
+    executor = Executor(tmp_venv, pool, config, io)
+    executor.execute([Install(package)])
+    verify_installed_distribution(tmp_venv, package)
+
+
 def test_executor_should_write_pep610_url_references_for_files(
     tmp_venv: VirtualEnv, pool: Pool, config: Config, io: BufferedIO
 ):