installer: deprecate old installer (setting `experimental.new-installer` to false)

src/poetry/console/application.py

@@ -335,7 +335,10 @@ class Application(BaseApplication):
             poetry.config,
             disable_cache=poetry.disable_cache,
         )
-        installer.use_executor(poetry.config.get("experimental.new-installer", False))
+        use_executor = poetry.config.get("experimental.new-installer", False)
+        if not use_executor:
+            # only set if false because the method is deprecated
+            installer.use_executor(False)
         command.set_installer(installer)
 
     def _load_plugins(self, io: IO | None = None) -> None:

src/poetry/console/commands/install.py

@@ -95,9 +95,10 @@ dependencies and not including the current project, run the command with the
 
         from poetry.masonry.builders.editable import EditableBuilder
 
-        self.installer.use_executor(
-            self.poetry.config.get("experimental.new-installer", False)
-        )
+        use_executor = self.poetry.config.get("experimental.new-installer", False)
+        if not use_executor:
+            # only set if false because the method is deprecated
+            self.installer.use_executor(False)
 
         if self.option("extras") and self.option("all-extras"):
             self.line_error(

src/poetry/console/commands/lock.py

@@ -35,9 +35,10 @@ file.
     loggers = ["poetry.repositories.pypi_repository"]
 
     def handle(self) -> int:
-        self.installer.use_executor(
-            self.poetry.config.get("experimental.new-installer", False)
-        )
+        use_executor = self.poetry.config.get("experimental.new-installer", False)
+        if not use_executor:
+            # only set if false because the method is deprecated
+            self.installer.use_executor(False)
 
         if self.option("check"):
             if self.poetry.locker.is_locked() and self.poetry.locker.is_fresh():

src/poetry/console/commands/update.py

@@ -41,9 +41,10 @@ class UpdateCommand(InstallerCommand):
     def handle(self) -> int:
         packages = self.argument("packages")
 
-        self.installer.use_executor(
-            self.poetry.config.get("experimental.new-installer", False)
-        )
+        use_executor = self.poetry.config.get("experimental.new-installer", False)
+        if not use_executor:
+            # only set if false because the method is deprecated
+            self.installer.use_executor(False)
 
         if packages:
             self.installer.whitelist({name: "*" for name in packages})

src/poetry/installation/installer.py

 from __future__ import annotations
 
+import warnings
+
 from typing import TYPE_CHECKING
 
 from cleo.io.null_io import NullIO
@@ -71,7 +73,7 @@ class Installer:
             )
 
         self._executor = executor
-        self._use_executor = False
+        self._use_executor = True
 
         self._installer = self._get_installer()
         if installed is None:
@@ -180,6 +182,14 @@ class Installer:
         return self
 
     def use_executor(self, use_executor: bool = True) -> Installer:
+        warnings.warn(
+            (
+                "Calling use_executor() is deprecated since it's true by default now"
+                " and deactivating it will be removed in a future release."
+            ),
+            DeprecationWarning,
+            stacklevel=2,
+        )
         self._use_executor = use_executor
 
         return self
@@ -366,6 +376,14 @@ class Installer:
         if self._use_executor:
             return self._executor.execute(operations)
 
+        self._io.write_error(
+            "<warning>"
+            "Setting `experimental.new-installer` to false is deprecated and"
+            " slated for removal in an upcoming minor release.\n"
+            "(Despite of the setting's name the new installer is not experimental!)"
+            "</warning>"
+        )
+
         if not operations and (self._execute_operations or self._dry_run):
             self._io.write_line("No dependencies to install or update")
 

src/poetry/utils/env.py

@@ -1917,6 +1917,17 @@ class NullEnv(SystemEnv):
         self._execute = execute
         self.executed: list[list[str]] = []
 
+    @property
+    def paths(self) -> dict[str, str]:
+        if self._paths is None:
+            self._paths = self.get_paths()
+            self._paths["platlib"] = str(self._path / "platlib")
+            self._paths["purelib"] = str(self._path / "purelib")
+            self._paths["scripts"] = str(self._path / "scripts")
+            self._paths["data"] = str(self._path / "data")
+
+        return self._paths
+
     def _run(self, cmd: list[str], **kwargs: Any) -> int | str:
         self.executed.append(cmd)
 
@@ -2044,17 +2055,6 @@ class MockEnv(NullEnv):
 
         return self._sys_path
 
-    @property
-    def paths(self) -> dict[str, str]:
-        if self._paths is None:
-            self._paths = self.get_paths()
-            self._paths["platlib"] = str(self._path / "platlib")
-            self._paths["purelib"] = str(self._path / "purelib")
-            self._paths["scripts"] = str(self._path / "scripts")
-            self._paths["data"] = str(self._path / "data")
-
-        return self._paths
-
     def get_marker_env(self) -> dict[str, Any]:
         if self._mock_marker_env is not None:
             return self._mock_marker_env

tests/console/commands/test_add.py

@@ -50,7 +50,8 @@ def tester(command_tester_factory: CommandTesterFactory) -> CommandTester:
 
 @pytest.fixture()
 def old_tester(tester: CommandTester) -> CommandTester:
-    tester.command.installer.use_executor(False)
+    with pytest.warns(DeprecationWarning):
+        tester.command.installer.use_executor(False)
 
     return tester
 

tests/console/conftest.py

@@ -166,7 +166,6 @@ def command_tester_factory(
                 executor=executor
                 or TestExecutor(env, poetry.pool, poetry.config, tester.io),
             )
-            installer.use_executor(True)
             command.set_installer(installer)
 
         return tester

tests/installation/test_installer.py

@@ -197,8 +197,6 @@ def installer(
         installed=installed,
         executor=Executor(env, pool, config, NullIO()),
     )
-    installer.use_executor(True)
-
     return installer
 
 
@@ -1961,8 +1959,6 @@ def test_installer_required_extras_should_not_be_removed_when_updating_single_de
         installed=installed,
         executor=Executor(env, pool, config, NullIO()),
     )
-    installer.use_executor()
-
     installer.update(True)
     installer.whitelist(["D"])
     installer.run()
@@ -1996,7 +1992,6 @@ def test_installer_required_extras_should_not_be_removed_when_updating_single_de
         installed=installed,
         executor=Executor(env, pool, config, NullIO()),
     )
-    installer.use_executor()
 
     package.add_dependency(Factory.create_dependency("poetry", {"version": "^0.12.0"}))
 
@@ -2025,8 +2020,6 @@ def test_installer_required_extras_should_not_be_removed_when_updating_single_de
         installed=installed,
         executor=Executor(env, pool, config, NullIO()),
     )
-    installer.use_executor()
-
     installer.update(True)
     installer.whitelist(["pytest"])
     installer.run()
@@ -2057,8 +2050,6 @@ def test_installer_required_extras_should_be_installed(
         installed=installed,
         executor=Executor(env, pool, config, NullIO()),
     )
-    installer.use_executor()
-
     package.add_dependency(
         Factory.create_dependency(
             "cachecontrol", {"version": "^0.12.5", "extras": ["filecache"]}
@@ -2085,8 +2076,6 @@ def test_installer_required_extras_should_be_installed(
         installed=installed,
         executor=Executor(env, pool, config, NullIO()),
     )
-    installer.use_executor()
-
     installer.update(True)
     installer.run()
 
@@ -2200,8 +2189,6 @@ def test_installer_can_install_dependencies_from_forced_source(
         installed=installed,
         executor=Executor(env, pool, config, NullIO()),
     )
-    installer.use_executor()
-
     installer.update(True)
     installer.run()
 
@@ -2267,7 +2254,6 @@ def test_run_installs_with_same_version_url_files(
             NullIO(),
         ),
     )
-    installer.use_executor(True)
     installer.run()
 
     expected = fixture("with-same-version-url-dependencies")
@@ -2332,8 +2318,6 @@ def test_installer_can_handle_old_lock_files(
         installed=installed,
         executor=Executor(MockEnv(), pool, config, NullIO()),
     )
-    installer.use_executor()
-
     installer.run()
 
     assert installer.executor.installations_count == 6
@@ -2353,8 +2337,6 @@ def test_installer_can_handle_old_lock_files(
             NullIO(),
         ),
     )
-    installer.use_executor()
-
     installer.run()
 
     # funcsigs will be added
@@ -2375,8 +2357,6 @@ def test_installer_can_handle_old_lock_files(
             NullIO(),
         ),
     )
-    installer.use_executor()
-
     installer.run()
 
     # colorama will be added
@@ -2640,7 +2620,6 @@ def test_installer_distinguishes_locked_packages_by_source(
             NullIO(),
         ),
     )
-    installer.use_executor(True)
     installer.run()
 
     # Results of installation are consistent with the platform requirements.

tests/installation/test_installer_old.py

@@ -4,6 +4,7 @@ import itertools
 
 from pathlib import Path
 from typing import TYPE_CHECKING
+from typing import Any
 
 import pytest
 
@@ -40,6 +41,10 @@ RESERVED_PACKAGES = ("pip", "setuptools", "wheel")
 
 
 class Installer(BaseInstaller):
+    def __init__(self, *args: Any, **kwargs: Any) -> None:
+        super().__init__(*args, **kwargs)
+        self._use_executor = False
+
     def _get_installer(self) -> NoopInstaller:
         return NoopInstaller()