introduce tool.poetry.self.version to define a constraint for the P…

…oetry version the project is compatible with

docs/pyproject.md

@@ -487,9 +487,18 @@ If you publish your package on PyPI, they will appear in the `Project Links` sec
 ## `self`
 
 In this section, you can specify requirements for Poetry itself.
+For example, you can specify a constraint for the Poetry version that is required
+for this project:
 
-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]
+version = ">=2.0"
+```
+
+If you are using a Poetry version that is not allowed by this constraint,
+an error will be raised.
+
+Further, you can specify that certain plugins are required for your project:
 
 ```toml
 [tool.poetry.self.plugins]

src/poetry/factory.py

@@ -10,9 +10,12 @@
 
 from cleo.io.null_io import NullIO
 from packaging.utils import canonicalize_name
+from poetry.core.constraints.version import Version
+from poetry.core.constraints.version import parse_constraint
 from poetry.core.factory import Factory as BaseFactory
 from poetry.core.packages.dependency_group import MAIN_GROUP
 
+from poetry.__version__ import __version__
 from poetry.config.config import Config
 from poetry.exceptions import PoetryException
 from poetry.json import validate_object
@@ -56,6 +59,17 @@ def create_poetry(
 
         base_poetry = super().create_poetry(cwd=cwd, with_groups=with_groups)
 
+        if version_str := base_poetry.pyproject.poetry_config.get("self", {}).get(
+            "version"
+        ):
+            version_constraint = parse_constraint(version_str)
+            version = Version.parse(__version__)
+            if not version_constraint.allows(version):
+                raise PoetryException(
+                    f"This project requires Poetry {version_constraint},"
+                    f" but you are using Poetry {version}"
+                )
+
         poetry_file = base_poetry.pyproject_path
         locker = Locker(poetry_file.parent / "poetry.lock", base_poetry.pyproject.data)
 

src/poetry/json/schemas/poetry.json

@@ -8,6 +8,11 @@
       "type": "object",
       "description": "Requirements for Poetry itself.",
       "properties": {
+        "version": {
+          "type": "string",
+          "description": "The version constraint for Poetry itself.",
+          "$ref": "#/definitions/dependency"
+        },
         "plugins": {
           "type": "object",
           "description": "Poetry plugins that are required for this project.",

tests/fixtures/self_version_not_ok/pyproject.toml

@@ -0,0 +1,8 @@
+[tool.poetry]
+package-mode = false
+
+[tool.poetry.self]
+version = "<1.2"
+
+[tool.poetry.dependencies]
+python = "^3.8"

tests/fixtures/self_version_ok/pyproject.toml

@@ -0,0 +1,8 @@
+[tool.poetry]
+package-mode = false
+
+[tool.poetry.self]
+version = ">=1.2"
+
+[tool.poetry.dependencies]
+python = "^3.8"

tests/json/fixtures/self_invalid_version.toml

@@ -0,0 +1,8 @@
+[tool.poetry]
+name = "foobar"
+version = "0.1.0"
+description = ""
+authors = ["Your Name <you@example.com>"]
+
+[tool.poetry.self]
+version = 2

tests/json/fixtures/self_valid.toml

@@ -4,5 +4,8 @@ version = "0.1.0"
 description = ""
 authors = ["Your Name <you@example.com>"]
 
+[tool.poetry.self]
+version = ">=2.0"
+
 [tool.poetry.self.plugins]
 foo = ">=1.0"

tests/json/test_schema.py

@@ -61,6 +61,15 @@ def test_self_valid() -> None:
     assert Factory.validate(content) == {"errors": [], "warnings": []}
 
 
+def test_self_invalid_version() -> None:
+    toml: dict[str, Any] = TOMLFile(FIXTURE_DIR / "self_invalid_version.toml").read()
+    content = toml["tool"]["poetry"]
+    assert Factory.validate(content) == {
+        "errors": ["data.self.version must be string"],
+        "warnings": [],
+    }
+
+
 def test_self_invalid_plugin() -> None:
     toml: dict[str, Any] = TOMLFile(FIXTURE_DIR / "self_invalid_plugin.toml").read()
     content = toml["tool"]["poetry"]

tests/test_factory.py

@@ -14,6 +14,7 @@
 from poetry.core.packages.package import Package
 from poetry.core.packages.vcs_dependency import VCSDependency
 
+from poetry.__version__ import __version__
 from poetry.exceptions import PoetryException
 from poetry.factory import Factory
 from poetry.plugins.plugin import Plugin
@@ -230,6 +231,23 @@ def test_create_poetry_non_package_mode(fixture_dir: FixtureDirGetter) -> None:
     assert not poetry.is_package_mode
 
 
+def test_create_poetry_version_ok(fixture_dir: FixtureDirGetter) -> None:
+    io = BufferedIO()
+    Factory().create_poetry(fixture_dir("self_version_ok"), io=io)
+
+    assert io.fetch_output() == ""
+    assert io.fetch_error() == ""
+
+
+def test_create_poetry_version_not_ok(fixture_dir: FixtureDirGetter) -> None:
+    with pytest.raises(PoetryException) as e:
+        Factory().create_poetry(fixture_dir("self_version_not_ok"))
+    assert (
+        str(e.value)
+        == f"This project requires Poetry <1.2, but you are using Poetry {__version__}"
+    )
+
+
 def test_poetry_with_default_source_legacy(
     fixture_dir: FixtureDirGetter, with_simple_keyring: None
 ) -> None: