Separate list depeendencies to a separate installer class

This allows other installers (such as uv) to reuse this code.

Signed-off-by: Bernát Gábor <bgabor8@bloomberg.net>

docs/changelog/3347.feature.rst

@@ -0,0 +1,2 @@
+Separate the list dependencies functionality to a separate abstract class allowing code reuse in plugins (such as
+``tox-uv``) - by :gaborbernat`.

src/tox/tox_env/python/pip/pip_install.py

@@ -2,6 +2,7 @@
 
 import logging
 import operator
+from abc import ABC, abstractmethod
 from collections import defaultdict
 from pathlib import Path
 from typing import TYPE_CHECKING, Any, Callable, Sequence
@@ -21,14 +22,36 @@
     from tox.tox_env.package import PathPackage
 
 
-class Pip(Installer[Python]):
-    """Pip is a python installer that can install packages as defined by PEP-508 and PEP-517."""
-
+class PythonInstallerList(Installer[Python], ABC):
     def __init__(self, tox_env: Python, with_list_deps: bool = True) -> None:  # noqa: FBT001, FBT002
         self._with_list_deps = with_list_deps
         super().__init__(tox_env)
 
     def _register_config(self) -> None:
+        if self._with_list_deps:  # pragma: no branch
+            self._env.conf.add_config(
+                keys=["list_dependencies_command"],
+                of_type=Command,
+                default=Command(self.freeze_cmd()),
+                desc="command used to list installed packages",
+            )
+
+    @abstractmethod
+    def freeze_cmd(self) -> list[str]:
+        raise NotImplementedError
+
+    def installed(self) -> list[str]:
+        cmd: Command = self._env.conf["list_dependencies_command"]
+        result = self._env.execute(cmd=cmd.args, stdin=StdinSource.OFF, run_id="freeze", show=False)
+        result.assert_success()
+        return result.out.splitlines()
+
+
+class Pip(PythonInstallerList):
+    """Pip is a python installer that can install packages as defined by PEP-508 and PEP-517."""
+
+    def _register_config(self) -> None:
+        super()._register_config()
         self._env.conf.add_config(
             keys=["pip_pre"],
             of_type=bool,
@@ -54,13 +77,9 @@ def _register_config(self) -> None:
             default=False,
             desc="Use the exact versions of installed deps as constraints, otherwise use the listed deps.",
         )
-        if self._with_list_deps:  # pragma: no branch
-            self._env.conf.add_config(
-                keys=["list_dependencies_command"],
-                of_type=Command,
-                default=Command(["python", "-m", "pip", "freeze", "--all"]),
-                desc="command used to list installed packages",
-            )
+
+    def freeze_cmd(self) -> list[str]:  # noqa: PLR6301
+        return ["python", "-m", "pip", "freeze", "--all"]
 
     def default_install_command(self, conf: Config, env_name: str | None) -> Command:  # noqa: ARG002
         isolated_flag = "-E" if self._env.base_python.version_info.major == 2 else "-I"  # noqa: PLR2004
@@ -82,12 +101,6 @@ def post_process_install_command(self, cmd: Command) -> Command:
                 install_command.pop(opts_at)
         return cmd
 
-    def installed(self) -> list[str]:
-        cmd: Command = self._env.conf["list_dependencies_command"]
-        result = self._env.execute(cmd=cmd.args, stdin=StdinSource.OFF, run_id="freeze", show=False)
-        result.assert_success()
-        return result.out.splitlines()
-
     def install(self, arguments: Any, section: str, of_type: str) -> None:
         if isinstance(arguments, PythonDeps):
             self._install_requirement_file(arguments, section, of_type)
@@ -239,4 +252,7 @@ def build_install_cmd(self, args: Sequence[str]) -> list[str]:
         return install_command[:opts_at] + list(args) + install_command[opts_at + 1 :]
 
 
-__all__ = ("Pip",)
+__all__ = [
+    "Pip",
+    "PythonInstallerList",
+]