introduce tool.poetry.self.plugins section to define Poetry plugins…

… that are required for the project (python-poetry#9547)

* when running `poetry install` and required plugins are not available in Poetry's own environment they are installed only for the project into .poetry/plugins inside the project folder
* when creating the application .poetry/plugins is added to the front of sys.path

Co-authored-by: Arun Babu Neelicattu <arun.neelicattu@gmail.com>

docs/plugins.md

@@ -255,6 +255,28 @@ You can also list all currently installed plugins by running:
 poetry self show plugins
 ```
 
+### Project plugins
+
+You can also specify that a plugin is required for your project
+in the `tool.poetry.self` section of the pyproject.toml file:
+
+```toml
+[tool.poetry.self.plugins]
+my-application-plugin = ">1.0"
+```
+
+If the plugin is not installed in Poetry's own environment when running `poetry install`,
+it will be installed only for the current project under `.poetry/plugins`
+in the project's directory.
+
+The syntax to specify `plugins` is the same as for [dependencies]({{< relref "managing-dependencies" >}}).
+
+{{% warning %}}
+You can even overwrite a plugin in Poetry's own environment with another version.
+However, if a plugin's dependencies are not compatible with packages in Poetry's own
+environment, installation will fail.
+{{% /warning %}}
+
 
 ## Maintaining a plugin
 

docs/pyproject.md

@@ -484,6 +484,21 @@ any custom url in the `urls` section.
 
 If you publish your package on PyPI, they will appear in the `Project Links` section.
 
+## `self`
+
+In this section, you can specify requirements for Poetry itself.
+
+You can also specify that a plugin is required for your project:
+You can specify that certain plugins are required for your project:
+
+```toml
+[tool.poetry.self.plugins]
+my-application-plugin = ">=1.0"
+my-plugin = ">=1.0,<2.0"
+```
+
+See [Project plugins]({{< relref "plugins#project-plugins" >}}) for more information.
+
 ## Poetry and PEP-517
 
 [PEP-517](https://www.python.org/dev/peps/pep-0517/) introduces a standard way

src/poetry/console/application.py

@@ -4,7 +4,9 @@
 import re
 
 from contextlib import suppress
+from functools import cached_property
 from importlib import import_module
+from pathlib import Path
 from typing import TYPE_CHECKING
 from typing import cast
 
@@ -111,20 +113,13 @@ def __init__(self) -> None:
 
     @property
     def poetry(self) -> Poetry:
-        from pathlib import Path
-
         from poetry.factory import Factory
 
         if self._poetry is not None:
             return self._poetry
 
-        project_path = Path.cwd()
-
-        if self._io and self._io.input.option("directory"):
-            project_path = Path(self._io.input.option("directory")).absolute()
-
         self._poetry = Factory().create_poetry(
-            cwd=project_path,
+            cwd=self._directory,
             io=self._io,
             disable_plugins=self._disable_plugins,
             disable_cache=self._disable_cache,
@@ -340,6 +335,7 @@ def _load_plugins(self, io: IO | None = None) -> None:
             from poetry.plugins.application_plugin import ApplicationPlugin
             from poetry.plugins.plugin_manager import PluginManager
 
+            PluginManager.add_project_plugin_path(self._directory)
             manager = PluginManager(ApplicationPlugin.group)
             manager.load_plugins()
             manager.activate(self)
@@ -382,6 +378,12 @@ def _default_definition(self) -> Definition:
 
         return definition
 
+    @cached_property
+    def _directory(self) -> Path:
+        if self._io and self._io.input.option("directory"):
+            return Path(self._io.input.option("directory")).absolute()
+        return Path.cwd()
+
 
 def main() -> int:
     exit_code: int = Application().run()

src/poetry/console/commands/install.py

@@ -6,6 +6,7 @@
 from cleo.helpers import option
 
 from poetry.console.commands.installer_command import InstallerCommand
+from poetry.plugins.plugin_manager import PluginManager
 
 
 if TYPE_CHECKING:
@@ -106,6 +107,8 @@ def handle(self) -> int:
 
         from poetry.masonry.builders.editable import EditableBuilder
 
+        PluginManager.ensure_project_plugins(self.poetry, self.io)
+
         if self.option("extras") and self.option("all-extras"):
             self.line_error(
                 "<error>You cannot specify explicit"

src/poetry/console/commands/self/show/plugins.py

@@ -70,9 +70,7 @@ def _system_project_handle(self) -> int:
         }
 
         for group in [ApplicationPlugin.group, Plugin.group]:
-            for entry_point in PluginManager(group).get_plugin_entry_points(
-                env=system_env
-            ):
+            for entry_point in PluginManager(group).get_plugin_entry_points():
                 assert entry_point.dist is not None
 
                 package = packages_by_name[canonicalize_name(entry_point.dist.name)]