reiterate version inference logic

MANIFEST.in

@@ -18,8 +18,10 @@ include CHANGELOG.md
 
 recursive-include testing *.bash
 prune nextgen
+prune .cursor
 
 recursive-include docs *.md
 include docs/examples/version_scheme_code/*.py
 include docs/examples/version_scheme_code/*.toml
 include mkdocs.yml
+include uv.lock

pyproject.toml

@@ -48,11 +48,8 @@ dependencies = [
   'typing-extensions; python_version < "3.10"',
 ]
 [project.optional-dependencies]
-rich = [
-  "rich",
-]
-toml = [
-]
+rich = ["rich"]
+toml = []
 
 [dependency-groups]
 docs = [

src/setuptools_scm/_config.py

@@ -291,24 +291,12 @@ def from_file(
         - **kwargs: additional keyword arguments to pass to the Configuration constructor
         """
 
-        try:
-            if pyproject_data is None:
-                pyproject_data = _read_pyproject(
-                    Path(name), missing_section_ok=missing_section_ok
-                )
-        except FileNotFoundError:
-            if missing_file_ok:
-                log.warning("File %s not found, using empty configuration", name)
-                pyproject_data = PyProjectData(
-                    path=Path(name),
-                    tool_name="setuptools_scm",
-                    project={},
-                    section={},
-                    is_required=False,
-                    section_present=False,
-                )
-            else:
-                raise
+        if pyproject_data is None:
+            pyproject_data = _read_pyproject(
+                Path(name),
+                missing_section_ok=missing_section_ok,
+                missing_file_ok=missing_file_ok,
+            )
         args = _get_args_for_pyproject(pyproject_data, dist_name, kwargs)
 
         args.update(read_toml_overrides(args["dist_name"]))

src/setuptools_scm/_integration/pyproject_reading.py

@@ -2,12 +2,12 @@
 
 import warnings
 
+from dataclasses import dataclass
 from pathlib import Path
-from typing import NamedTuple
 from typing import Sequence
 
 from .. import _log
-from .setuptools import read_dist_name_from_setup_cfg
+from .._requirement_cls import extract_package_name
 from .toml import TOML_RESULT
 from .toml import read_toml_content
 
@@ -16,13 +16,39 @@
 _ROOT = "root"
 
 
-class PyProjectData(NamedTuple):
+@dataclass
+class PyProjectData:
     path: Path
     tool_name: str
     project: TOML_RESULT
     section: TOML_RESULT
     is_required: bool
     section_present: bool
+    project_present: bool
+
+    @classmethod
+    def for_testing(
+        cls,
+        is_required: bool = False,
+        section_present: bool = False,
+        project_present: bool = False,
+        project_name: str | None = None,
+    ) -> PyProjectData:
+        """Create a PyProjectData instance for testing purposes."""
+        if project_name is not None:
+            project = {"name": project_name}
+            assert project_present
+        else:
+            project = {}
+        return cls(
+            path=Path("pyproject.toml"),
+            tool_name="setuptools_scm",
+            project=project,
+            section={},
+            is_required=is_required,
+            section_present=section_present,
+            project_present=project_present,
+        )
 
     @property
     def project_name(self) -> str | None:
@@ -33,6 +59,10 @@ def verify_dynamic_version_when_required(self) -> None:
         if self.is_required and not self.section_present:
             # When setuptools-scm is in build-system.requires but no tool section exists,
             # we need to verify that dynamic=['version'] is set in the project section
+            # But only if there's actually a project section
+            if not self.project_present:
+                # No project section, so don't auto-activate setuptools_scm
+                return
             dynamic = self.project.get("dynamic", [])
             if "version" not in dynamic:
                 raise ValueError(
@@ -43,29 +73,41 @@ def verify_dynamic_version_when_required(self) -> None:
 
 
 def has_build_package(
-    requires: Sequence[str], build_package_names: Sequence[str]
+    requires: Sequence[str], canonical_build_package_name: str
 ) -> bool:
     for requirement in requires:
-        import re
-
-        # Remove extras like [toml] first
-        clean_req = re.sub(r"\[.*?\]", "", requirement)
-        # Split on version operators and take first part
-        package_name = re.split(r"[><=!~]", clean_req)[0].strip().lower()
-        if package_name in build_package_names:
+        package_name = extract_package_name(requirement)
+        if package_name == canonical_build_package_name:
             return True
     return False
 
 
 def read_pyproject(
     path: Path = Path("pyproject.toml"),
     tool_name: str = "setuptools_scm",
-    build_package_names: Sequence[str] = ("setuptools_scm", "setuptools-scm"),
+    canonical_build_package_name: str = "setuptools-scm",
     missing_section_ok: bool = False,
+    missing_file_ok: bool = False,
 ) -> PyProjectData:
-    defn = read_toml_content(path)
+    try:
+        defn = read_toml_content(path)
+    except FileNotFoundError:
+        if missing_file_ok:
+            log.warning("File %s not found, using empty configuration", path)
+            return PyProjectData(
+                path=path,
+                tool_name=tool_name,
+                project={},
+                section={},
+                is_required=False,
+                section_present=False,
+                project_present=False,
+            )
+        else:
+            raise
+
     requires: list[str] = defn.get("build-system", {}).get("requires", [])
-    is_required = has_build_package(requires, build_package_names)
+    is_required = has_build_package(requires, canonical_build_package_name)
 
     try:
         section = defn.get("tool", {})[tool_name]
@@ -87,8 +129,9 @@ def read_pyproject(
             section_present = False
 
     project = defn.get("project", {})
+    project_present = "project" in defn
     pyproject_data = PyProjectData(
-        path, tool_name, project, section, is_required, section_present
+        path, tool_name, project, section, is_required, section_present, project_present
     )
 
     # Verify dynamic version when setuptools-scm is used as build dependency indicator
@@ -121,8 +164,6 @@ def get_args_for_pyproject(
     if dist_name is None:
         # minimal pep 621 support for figuring the pretend keys
         dist_name = pyproject.project_name
-    if dist_name is None:
-        dist_name = read_dist_name_from_setup_cfg()
     if _ROOT in kwargs:
         if kwargs[_ROOT] is None:
             kwargs.pop(_ROOT, None)

src/setuptools_scm/_integration/setup_cfg.py

@@ -0,0 +1,21 @@
+from __future__ import annotations
+
+import os
+
+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
+    import configparser
+
+    parser = configparser.ConfigParser()
+    parser.read([input], encoding="utf-8")
+    dist_name = parser.get("metadata", "name", fallback=None)
+    return dist_name
+
+
+def _dist_name_from_legacy(dist: setuptools.Distribution) -> str | None:
+    return dist.metadata.name or read_dist_name_from_setup_cfg()