poetry: expose build-system dependencies

src/poetry/core/poetry.py

@@ -1,14 +1,23 @@
 from __future__ import annotations
 
+import logging
+
+from pathlib import Path
 from typing import TYPE_CHECKING
 from typing import Any
 
+from packaging.utils import canonicalize_name
+
+from poetry.core.packages.dependency import Dependency
+from poetry.core.packages.directory_dependency import DirectoryDependency
+from poetry.core.packages.file_dependency import FileDependency
 from poetry.core.pyproject.toml import PyProjectTOML
 
 
-if TYPE_CHECKING:
-    from pathlib import Path
+logger = logging.getLogger(__name__)
 
+
+if TYPE_CHECKING:
     from poetry.core.packages.project_package import ProjectPackage
 
 
@@ -23,6 +32,7 @@ def __init__(
         self._pyproject = pyproject_type(file)
         self._package = package
         self._local_config = local_config
+        self._build_system_dependencies: list[Dependency] | None = None
 
     @property
     def pyproject(self) -> PyProjectTOML:
@@ -48,3 +58,37 @@ def local_config(self) -> dict[str, Any]:
 
     def get_project_config(self, config: str, default: Any = None) -> Any:
         return self._local_config.get("config", {}).get(config, default)
+
+    @property
+    def build_system_dependencies(self) -> list[Dependency]:
+        if self._build_system_dependencies is None:
+            build_system = self.pyproject.build_system
+            self._build_system_dependencies = []
+
+            for requirement in build_system.requires:
+                dependency = None
+                try:
+                    dependency = Dependency.create_from_pep_508(requirement)
+                except ValueError:
+                    # PEP 517 requires can be path if not PEP 508
+                    path = Path(requirement)
+
+                    if path.is_file():
+                        dependency = FileDependency(
+                            name=canonicalize_name(path.name), path=path
+                        )
+                    elif path.is_dir():
+                        dependency = DirectoryDependency(
+                            name=canonicalize_name(path.name), path=path
+                        )
+
+                # skip since we could not determine requirement
+                if dependency:
+                    self._build_system_dependencies.append(dependency)
+                else:
+                    logger.debug(
+                        "Skipping build system dependency - could not determine requirement type: %s",
+                        requirement,
+                    )
+
+        return self._build_system_dependencies

tests/test_factory.py

@@ -11,19 +11,19 @@
 
 from poetry.core.constraints.version import parse_constraint
 from poetry.core.factory import Factory
+from poetry.core.packages.dependency import Dependency
+from poetry.core.packages.directory_dependency import DirectoryDependency
+from poetry.core.packages.file_dependency import FileDependency
 from poetry.core.packages.url_dependency import URLDependency
 from poetry.core.packages.vcs_dependency import VCSDependency
+from poetry.core.pyproject.tables import BuildSystem
 from poetry.core.utils._compat import tomllib
 from poetry.core.version.markers import SingleMarker
 
 
 if TYPE_CHECKING:
     from pytest import LogCaptureFixture
 
-    from poetry.core.packages.dependency import Dependency
-    from poetry.core.packages.directory_dependency import DirectoryDependency
-    from poetry.core.packages.file_dependency import FileDependency
-
 
 fixtures_dir = Path(__file__).parent / "fixtures"
 
@@ -976,3 +976,79 @@ def test_all_classifiers_unique_even_if_classifiers_is_duplicated() -> None:
         "Programming Language :: Python :: 3.13",
         "Topic :: Software Development :: Build Tools",
     ]
+
+
+@pytest.mark.parametrize(
+    ("project", "expected"),
+    [
+        ("sample_project", set(BuildSystem().dependencies)),
+        (
+            "project_with_build_system_requires",
+            {
+                Dependency.create_from_pep_508("poetry-core"),
+                Dependency.create_from_pep_508("Cython (>=0.29.6,<0.30.0)"),
+            },
+        ),
+    ],
+)
+def test_poetry_build_system_dependencies_from_fixtures(
+    project: str, expected: set[Dependency]
+) -> None:
+    poetry = Factory().create_poetry(fixtures_dir / project)
+    assert set(poetry.build_system_dependencies) == expected
+
+
+SAMPLE_PROJECT_DIRECTORY = fixtures_dir / "sample_project"
+SIMPLE_PROJECT_WHEEL = (
+    fixtures_dir
+    / "simple_project"
+    / "dist"
+    / "simple_project-1.2.3-py2.py3-none-any.whl"
+)
+
+
+@pytest.mark.parametrize(
+    ("requires", "expected"),
+    [
+        (BuildSystem().requires, set(BuildSystem().dependencies)),
+        (["poetry-core>=2.0.0"], {Dependency("poetry-core", ">=2.0.0")}),
+        (["****invalid****"], set()),
+        (
+            ["hatch", "numpy ; sys_platform == 'win32'"],
+            {
+                Dependency("hatch", "*"),
+                Dependency.create_from_pep_508("numpy ; sys_platform == 'win32'"),
+            },
+        ),
+        (
+            [SAMPLE_PROJECT_DIRECTORY.as_posix()],
+            {
+                DirectoryDependency(
+                    SAMPLE_PROJECT_DIRECTORY.name, SAMPLE_PROJECT_DIRECTORY
+                )
+            },
+        ),
+        (
+            [SIMPLE_PROJECT_WHEEL.as_posix()],
+            {FileDependency(SIMPLE_PROJECT_WHEEL.name, SIMPLE_PROJECT_WHEEL)},
+        ),
+    ],
+)
+def test_poetry_build_system_dependencies(
+    requires: list[str], expected: set[Dependency], temporary_directory: Path
+) -> None:
+    pyproject_toml = temporary_directory / "pyproject.toml"
+    build_system_requires = ", ".join(f'"{require}"' for require in requires)
+    content = f"""[project]
+name = "my-package"
+version = "1.2.3"
+
+[build-system]
+requires = [{build_system_requires}]
+build-backend = "some.api.we.do.not.care.about"
+
+"""
+    pyproject_toml.write_text(content)
+    poetry = Factory().create_poetry(temporary_directory)
+
+    assert set(poetry.build_system_dependencies) == expected