fix #919: restore legacy version-file behaviour for external callers …

…+ add Deprecation warning

CHANGELOG.rst

@@ -3,6 +3,8 @@ v8.0.2
 
 bugfix
 ------
+
+* fix #919: restore legacy version-file behaviour for external callers + add Deprecation warning
 * fix #918: use packaging from setuptools for self-build
 * fix #914: ignore the deprecated git archival plugin as its integrated now
 * fix #912: ensure mypy safety of the version template + regression test

src/setuptools_scm/_cli.py

@@ -31,7 +31,7 @@ def main(args: list[str] | None = None) -> None:
         )
         config = Configuration(inferred_root)
 
-    version = _get_version(config)
+    version = _get_version(config, force_write_version_files=False)
     if version is None:
         raise SystemExit("ERROR: no version found for", opts)
     if opts.strip_dev:

src/setuptools_scm/_get_version_impl.py

@@ -84,12 +84,20 @@ def write_version_files(
 
 
 def _get_version(
-    config: Configuration, force_write_version_files: bool = False
+    config: Configuration, force_write_version_files: bool | None = None
 ) -> str | None:
     parsed_version = parse_version(config)
     if parsed_version is None:
         return None
     version_string = _format_version(parsed_version)
+    if force_write_version_files is None:
+        force_write_version_files = True
+        warnings.warn(
+            "force_write_version_files ought to be set,"
+            " presuming the legacy True value",
+            DeprecationWarning,
+        )
+
     if force_write_version_files:
         write_version_files(config, version=version_string, scm_version=parsed_version)
 

testing/test_basic_api.py

@@ -242,3 +242,20 @@ def __repr__(self) -> str:
     #  to create a test?
     # monkeypatch.setenv(setuptools_scm.PRETEND_KEY, "1.0.1")
     # assert setuptools_scm.get_version(version_cls=MyVersion) == "1"
+
+
+def test_internal_get_version_warns_for_version_files(tmp_path: Path) -> None:
+    tmp_path.joinpath("PKG-INFO").write_text("Version: 0.1")
+    c = Configuration(root=tmp_path, fallback_root=tmp_path)
+    with pytest.warns(
+        DeprecationWarning,
+        match="force_write_version_files ought to be set,"
+        " presuming the legacy True value",
+    ):
+        ver = setuptools_scm._get_version(c)
+    assert ver == "0.1"
+
+    # force write won't write as no version file is configured
+    assert setuptools_scm._get_version(c, force_write_version_files=False) == ver
+
+    assert setuptools_scm._get_version(c, force_write_version_files=True) == ver