read version from setup.cfg

Author: RonnyPfannschmidt

src/setuptools_scm/_integration/setup_cfg.py

@@ -2,20 +2,36 @@
 
 import os
 
+from dataclasses import dataclass
+from pathlib import Path
+
 import setuptools
 
 
-def read_dist_name_from_setup_cfg(
-    input: str | os.PathLike[str] = "setup.cfg",
-) -> str | None:
-    # minimal effort to read dist_name off setup.cfg metadata
+@dataclass
+class SetuptoolsBasicData:
+    path: Path
+    name: str | None
+    version: str | None
+
+
+def read_setup_cfg(input: str | os.PathLike[str] = "setup.cfg") -> SetuptoolsBasicData:
+    """Parse setup.cfg and return unified data. Does not raise if file is missing."""
     import configparser
 
+    path = Path(input)
     parser = configparser.ConfigParser()
     parser.read([input], encoding="utf-8")
-    dist_name = parser.get("metadata", "name", fallback=None)
-    return dist_name
+
+    name = parser.get("metadata", "name", fallback=None)
+    version = parser.get("metadata", "version", fallback=None)
+    return SetuptoolsBasicData(path=path, name=name, version=version)
 
 
-def _dist_name_from_legacy(dist: setuptools.Distribution) -> str | None:
-    return dist.metadata.name or read_dist_name_from_setup_cfg()
+def extract_from_legacy(dist: setuptools.Distribution) -> SetuptoolsBasicData:
+    base = read_setup_cfg()
+    if base.name is None:
+        base.name = dist.metadata.name
+    if base.version is None:
+        base.version = dist.metadata.version
+    return base

src/setuptools_scm/_integration/setuptools.py

@@ -12,7 +12,7 @@
 from .. import _types as _t
 from .pyproject_reading import PyProjectData
 from .pyproject_reading import read_pyproject
-from .setup_cfg import _dist_name_from_legacy
+from .setup_cfg import extract_from_legacy
 from .toml import InvalidTomlError
 from .version_inference import get_version_inference_config
 
@@ -85,7 +85,8 @@ def version_keyword(
         "dist_name may not be specified in the setup keyword "
     )
 
-    dist_name: str | None = _dist_name_from_legacy(dist)
+    legacy_data = extract_from_legacy(dist)
+    dist_name: str | None = legacy_data.name
 
     was_set_by_infer = getattr(dist, "_setuptools_scm_version_set_by_infer", False)
 
@@ -101,7 +102,7 @@ def version_keyword(
 
     result = _get_version_inference_config(
         dist_name=dist_name,
-        current_version=dist.metadata.version,
+        current_version=legacy_data.version or pyproject_data.project.get("version"),
         pyproject_data=pyproject_data,
         overrides=overrides,
         was_set_by_infer=was_set_by_infer,
@@ -125,7 +126,8 @@ def infer_version(
 
     _log_hookstart("infer_version", dist)
 
-    dist_name = _dist_name_from_legacy(dist)
+    legacy_data = extract_from_legacy(dist)
+    dist_name = legacy_data.name
 
     try:
         pyproject_data = read_pyproject(_given_result=_given_pyproject_data)
@@ -138,7 +140,7 @@ def infer_version(
 
     result = _get_version_inference_config(
         dist_name=dist_name,
-        current_version=dist.metadata.version,
+        current_version=legacy_data.version or pyproject_data.project.get("version"),
         pyproject_data=pyproject_data,
     )
     result.apply(dist)

testing/test_integration.py

@@ -18,6 +18,7 @@
 
 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
 from setuptools_scm._requirement_cls import extract_package_name
 
 if TYPE_CHECKING:
@@ -645,11 +646,64 @@ def test_unicode_in_setup_cfg(tmp_path: Path) -> None:
         ),
         encoding="utf-8",
     )
-    from setuptools_scm._integration.setup_cfg import read_dist_name_from_setup_cfg
+    from setuptools_scm._integration.setup_cfg import read_setup_cfg
 
-    name = read_dist_name_from_setup_cfg(cfg)
+    name = read_setup_cfg(cfg).name
     assert name == "configparser"
 
+    # also ensure we can parse a version if present (legacy projects)
+    cfg.write_text(
+        textwrap.dedent(
+            """
+            [metadata]
+            name = configparser
+            version = 1.2.3
+            """
+        ),
+        encoding="utf-8",
+    )
+
+    data = read_setup_cfg(cfg)
+    assert isinstance(data, SetuptoolsBasicData)
+    assert data.name == "configparser"
+    assert data.version == "1.2.3"
+
+
+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
+    monkeypatch.chdir(tmp_path)
+
+    dist = create_clean_distribution("legacy-proj")
+
+    # Using keyword should detect an existing version via setup.cfg and avoid inferring
+    from setuptools_scm._integration import setuptools as setuptools_integration
+    from setuptools_scm._integration.pyproject_reading import PyProjectData
+
+    setuptools_integration.version_keyword(
+        dist,
+        "use_scm_version",
+        True,
+        _given_pyproject_data=PyProjectData.empty(tmp_path / "pyproject.toml"),
+    )
+
+    # setuptools_scm should not set a version when setup.cfg already provided one
+    assert dist.metadata.version is None
+
 
 def test_setuptools_version_keyword_ensures_regex(
     wd: WorkDir,