reiterate version inference logic again

the decission tree is massively simplified

Author: RonnyPfannschmidt

src/setuptools_scm/_integration/pyproject_reading.py

@@ -35,6 +35,7 @@ class PyProjectData:
     @classmethod
     def for_testing(
         cls,
+        *,
         is_required: bool = False,
         section_present: bool = False,
         project_present: bool = False,

src/setuptools_scm/_integration/setup_cfg.py

@@ -28,8 +28,12 @@ def read_setup_cfg(input: str | os.PathLike[str] = "setup.cfg") -> SetuptoolsBas
     return SetuptoolsBasicData(path=path, name=name, version=version)
 
 
-def extract_from_legacy(dist: setuptools.Distribution) -> SetuptoolsBasicData:
-    base = read_setup_cfg()
+def extract_from_legacy(
+    dist: setuptools.Distribution,
+    *,
+    _given_legacy_data: SetuptoolsBasicData | None = None,
+) -> SetuptoolsBasicData:
+    base = _given_legacy_data if _given_legacy_data is not None else read_setup_cfg()
     if base.name is None:
         base.name = dist.metadata.name
     if base.version is None:

src/setuptools_scm/_integration/setuptools.py

@@ -11,6 +11,7 @@
 from .. import _types as _t
 from .pyproject_reading import PyProjectData
 from .pyproject_reading import read_pyproject
+from .setup_cfg import SetuptoolsBasicData
 from .setup_cfg import extract_from_legacy
 from .toml import InvalidTomlError
 from .version_inference import get_version_inference_config
@@ -69,6 +70,7 @@ def version_keyword(
     value: bool | dict[str, Any] | Callable[[], dict[str, Any]],
     *,
     _given_pyproject_data: _t.GivenPyProjectResult = None,
+    _given_legacy_data: SetuptoolsBasicData | None = None,
     _get_version_inference_config: _t.GetVersionInferenceConfig = get_version_inference_config,
 ) -> None:
     """apply version infernce when setup(use_scm_version=...) is used
@@ -84,7 +86,7 @@ def version_keyword(
         "dist_name may not be specified in the setup keyword "
     )
 
-    legacy_data = extract_from_legacy(dist)
+    legacy_data = extract_from_legacy(dist, _given_legacy_data=_given_legacy_data)
     dist_name: str | None = legacy_data.name
 
     was_set_by_infer = getattr(dist, "_setuptools_scm_version_set_by_infer", False)
@@ -124,6 +126,7 @@ def infer_version(
     dist: setuptools.Distribution,
     *,
     _given_pyproject_data: _t.GivenPyProjectResult = None,
+    _given_legacy_data: SetuptoolsBasicData | None = None,
     _get_version_inference_config: _t.GetVersionInferenceConfig = get_version_inference_config,
 ) -> None:
     """apply version inference from the finalize_options hook
@@ -135,7 +138,7 @@ def infer_version(
 
     _log_hookstart("infer_version", dist)
 
-    legacy_data = extract_from_legacy(dist)
+    legacy_data = extract_from_legacy(dist, _given_legacy_data=_given_legacy_data)
     dist_name = legacy_data.name
 
     try:

src/setuptools_scm/_integration/version_inference.py

@@ -5,6 +5,8 @@
 from typing import Any
 from typing import Union
 
+from setuptools import Distribution
+
 from .. import _log
 
 if TYPE_CHECKING:
@@ -21,7 +23,7 @@ class VersionInferenceConfig:
     pyproject_data: PyProjectData | None
     overrides: dict[str, Any] | None
 
-    def apply(self, dist: Any) -> None:
+    def apply(self, dist: Distribution) -> None:
         """Apply version inference to the distribution."""
         from .. import _config as _config_module
         from .._get_version_impl import _get_version
@@ -42,34 +44,32 @@ def apply(self, dist: Any) -> None:
 
         # Mark that this version was set by infer_version if overrides is None (infer_version context)
         if self.overrides is None:
-            dist._setuptools_scm_version_set_by_infer = True
+            dist._setuptools_scm_version_set_by_infer = True  # type: ignore[attr-defined]
 
 
 @dataclass
-class VersionInferenceError:
+class VersionInferenceWarning:
     """Error message for user."""
 
     message: str
-    should_warn: bool = False
 
-    def apply(self, dist: Any) -> None:
+    def apply(self, dist: Distribution) -> None:
         """Apply error handling to the distribution."""
         import warnings
 
-        if self.should_warn:
-            warnings.warn(self.message)
+        warnings.warn(self.message)
 
 
 class VersionInferenceNoOp:
     """No operation result - silent skip."""
 
-    def apply(self, dist: Any) -> None:
+    def apply(self, dist: Distribution) -> None:
         """Apply no-op to the distribution."""
 
 
 VersionInferenceResult = Union[
     VersionInferenceConfig,  # Proceed with inference
-    VersionInferenceError,  # Show error/warning
+    VersionInferenceWarning,  # Show warning
     VersionInferenceNoOp,  # Don't infer (silent)
 ]
 
@@ -92,37 +92,21 @@ def get_version_inference_config(
     Returns:
         VersionInferenceResult with the decision and configuration
     """
-    # Normalize name from project metadata when not provided
-    if dist_name is None:
-        dist_name = pyproject_data.project_name
 
-    # Never infer a version for setuptools-scm itself
-    if dist_name == "setuptools-scm":
-        return VersionInferenceNoOp()
+    config = VersionInferenceConfig(
+        dist_name=dist_name,
+        pyproject_data=pyproject_data,
+        overrides=overrides,
+    )
+
+    inference_implied = pyproject_data.should_infer() or overrides is not None
 
-    # If a version already exists, short-circuit by context
-    if current_version is not None:
-        if overrides is None:
-            # infer_version called and a version is already present → do nothing
-            return VersionInferenceNoOp()
+    if inference_implied:
+        if current_version is None:
+            return config
         else:
-            # version_keyword context - always warn if version already set
-            return VersionInferenceError(
+            return VersionInferenceWarning(
                 f"version of {dist_name} already set",
-                should_warn=pyproject_data.should_infer(),
             )
-
-    # No version present yet
-    if overrides is not None:
-        # version_keyword path: any overrides (empty or not) mean we should infer
-        return VersionInferenceConfig(
-            dist_name=dist_name, pyproject_data=pyproject_data, overrides=overrides
-        )
-
-    # infer_version path: only infer when [tool.setuptools_scm] is present
-    if pyproject_data.should_infer():
-        return VersionInferenceConfig(
-            dist_name=dist_name, pyproject_data=pyproject_data, overrides=overrides
-        )
-
-    return VersionInferenceNoOp()
+    else:
+        return VersionInferenceNoOp()

src/setuptools_scm/_types.py

@@ -10,6 +10,8 @@
 from typing import Tuple
 from typing import Union
 
+from setuptools import Distribution
+
 if TYPE_CHECKING:
     import sys
 
@@ -42,7 +44,7 @@
 class VersionInferenceApplicable(Protocol):
     """A result object from version inference decision that can be applied to a dist."""
 
-    def apply(self, dist: object) -> None:  # pragma: no cover - structural type
+    def apply(self, dist: Distribution) -> None:  # pragma: no cover - structural type
         ...
 
 

testing/test_integration.py

@@ -672,35 +672,37 @@ def test_unicode_in_setup_cfg(tmp_path: Path) -> None:
 def test_setup_cfg_version_prevents_inference_version_keyword(
     tmp_path: Path, monkeypatch: pytest.MonkeyPatch
 ) -> None:
-    # Legacy project with version in setup.cfg
-    cfg = tmp_path / "setup.cfg"
-    cfg.write_text(
-        textwrap.dedent(
-            """
-            [metadata]
-            name = legacy-proj
-            version = 0.9.0
-            """
-        ),
-        encoding="utf-8",
-    )
-
-    # No pyproject.toml
+    # Legacy project setup - we construct the data directly since files are not read anyway
     monkeypatch.chdir(tmp_path)
 
     dist = create_clean_distribution("legacy-proj")
 
-    # Using keyword should detect an existing version via setup.cfg and avoid inferring
+    # Using keyword should detect an existing version via legacy data and avoid inferring
     from setuptools_scm._integration import setuptools as setuptools_integration
     from setuptools_scm._integration.pyproject_reading import PyProjectData
+    from setuptools_scm._integration.setup_cfg import SetuptoolsBasicData
 
-    setuptools_integration.version_keyword(
-        dist,
-        "use_scm_version",
-        True,
-        _given_pyproject_data=PyProjectData.empty(tmp_path / "pyproject.toml"),
+    # Construct PyProjectData directly without requiring build backend inference
+    pyproject_data = PyProjectData.for_testing(
+        is_required=False,  # setuptools-scm not required
+        section_present=False,  # no [tool.setuptools_scm] section
+        project_present=False,  # no [project] section
     )
 
+    # Construct legacy data with version from setup.cfg
+    legacy_data = SetuptoolsBasicData(
+        path=tmp_path / "setup.cfg", name="legacy-proj", version="0.9.0"
+    )
+
+    with pytest.warns(UserWarning, match="version of legacy-proj already set"):
+        setuptools_integration.version_keyword(
+            dist,
+            "use_scm_version",
+            True,
+            _given_pyproject_data=pyproject_data,
+            _given_legacy_data=legacy_data,
+        )
+
     # setuptools_scm should not set a version when setup.cfg already provided one
     assert dist.metadata.version is None