Add tox_on_install plugin hook

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

docs/changelog/2687.feature.rst

@@ -0,0 +1 @@
+Add :meth:`tox_on_install <tox.plugin.spec.tox_on_install>` plugin hook - by :user:`gaborbernat`.

src/tox/plugin/manager.py

@@ -3,6 +3,7 @@
 
 from pathlib import Path
 from types import ModuleType
+from typing import Any
 
 import pluggy
 
@@ -76,6 +77,9 @@ def tox_before_run_commands(self, tox_env: ToxEnv) -> None:
     def tox_after_run_commands(self, tox_env: ToxEnv, exit_code: int, outcomes: list[Outcome]) -> None:
         self.manager.hook.tox_after_run_commands(tox_env=tox_env, exit_code=exit_code, outcomes=outcomes)
 
+    def tox_on_install(self, tox_env: ToxEnv, arguments: Any, section: str, of_type: str) -> None:
+        self.manager.hook.tox_on_install(tox_env=tox_env, arguments=arguments, section=section, of_type=of_type)
+
     def load_plugins(self, path: Path) -> None:
         for _plugin in self.manager.get_plugins():  # make sure we start with a clean state, repeated in memory run
             self.manager.unregister(_plugin)

src/tox/plugin/spec.py

@@ -83,6 +83,18 @@ def tox_after_run_commands(tox_env: ToxEnv, exit_code: int, outcomes: list[Outco
     """
 
 
+@_spec
+def tox_on_install(tox_env: ToxEnv, arguments: Any, section: str, of_type: str) -> None:  # noqa: U100
+    """
+    Called before executing an installation command.
+
+    :param tox_env: the tox environment where the command runs in
+    :param arguments: installation arguments
+    :param section: section of the installation
+    :param of_type: type of the installation
+    """
+
+
 __all__ = [
     "NAME",
     "tox_register_tox_env",
@@ -91,4 +103,5 @@ def tox_after_run_commands(tox_env: ToxEnv, exit_code: int, outcomes: list[Outco
     "tox_add_env_config",
     "tox_before_run_commands",
     "tox_after_run_commands",
+    "tox_on_install",
 ]

src/tox/tox_env/api.py

@@ -89,6 +89,12 @@ def executor(self) -> Execute:
     def installer(self) -> Installer[Any]:
         raise NotImplementedError
 
+    def _install(self, arguments: Any, section: str, of_type: str) -> None:
+        from tox.plugin.manager import MANAGER
+
+        MANAGER.tox_on_install(self, arguments, section, of_type)
+        self.installer.install(arguments, section, of_type)
+
     def __repr__(self) -> str:
         return f"{self.__class__.__name__}(name={self.conf['env_name']})"
 

src/tox/tox_env/python/package.py

@@ -55,7 +55,7 @@ def __init__(self, create_args: ToxEnvCreateArgs) -> None:
     def _setup_env(self) -> None:
         """setup the tox environment"""
         super()._setup_env()
-        self.installer.install(self.requires(), PythonPackageToxEnv.__name__, "requires")
+        self._install(self.requires(), PythonPackageToxEnv.__name__, "requires")
 
     @abstractmethod
     def requires(self) -> tuple[Requirement, ...] | PythonDeps:

src/tox/tox_env/python/runner.py

@@ -100,7 +100,7 @@ def _setup_env(self) -> None:
 
     def _install_deps(self) -> None:
         requirements_file: PythonDeps = self.conf["deps"]
-        self.installer.install(requirements_file, PythonRun.__name__, "deps")
+        self._install(requirements_file, PythonRun.__name__, "deps")
 
     def _build_packages(self) -> list[Package]:
         package_env = self.package_env

src/tox/tox_env/python/virtual_env/package/pyproject.py

@@ -148,13 +148,13 @@ def _setup_env(self) -> None:
             if not self._frontend.optional_hooks["build_editable"]:
                 raise BuildEditableNotSupported
             build_requires = self._frontend.get_requires_for_build_editable().requires
-            self.installer.install(build_requires, PythonPackageToxEnv.__name__, "requires_for_build_editable")
+            self._install(build_requires, PythonPackageToxEnv.__name__, "requires_for_build_editable")
         if "wheel" in self.builds:
             build_requires = self._frontend.get_requires_for_build_wheel().requires
-            self.installer.install(build_requires, PythonPackageToxEnv.__name__, "requires_for_build_wheel")
+            self._install(build_requires, PythonPackageToxEnv.__name__, "requires_for_build_wheel")
         if "sdist" in self.builds or "external" in self.builds:
             build_requires = self._frontend.get_requires_for_build_sdist().requires
-            self.installer.install(build_requires, PythonPackageToxEnv.__name__, "requires_for_build_sdist")
+            self._install(build_requires, PythonPackageToxEnv.__name__, "requires_for_build_sdist")
 
     def _teardown(self) -> None:
         executor = self._frontend.backend_executor

src/tox/tox_env/runner.py

@@ -170,7 +170,7 @@ def _register_package_conf(self) -> bool:
 
     def _setup_pkg(self) -> None:
         self._packages = self._build_packages()
-        self.installer.install(self._packages, RunToxEnv.__name__, "package")
+        self._install(self._packages, RunToxEnv.__name__, "package")
         self._handle_journal_package(self.journal, self._packages)
 
     @staticmethod