fix pypa#549: when CommandNotFound is triggered, try the fallbacks

supersedes pypa#783

CHANGELOG.rst

@@ -38,6 +38,7 @@ features
 * support passing log levels to SETUPTOOLS_SCM_DEBUG
 * support using rich.logging as console log handler if installed
 * fix #527: type annotation in default version template
+* fix #549: use fallbacks when scm search raises CommandNotFoundError
 
 bugfixes
 --------

src/setuptools_scm/_get_version.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import logging
 import re
 import warnings
 from pathlib import Path
@@ -9,27 +10,34 @@
 
 from . import _config
 from . import _entrypoints
+from . import _run_cmd
 from . import _types as _t
 from ._config import Configuration
 from ._overrides import _read_pretended_version_for
 from ._version_cls import _validate_version_cls
 from .version import format_version as _format_version
 from .version import ScmVersion
 
+_log = logging.getLogger(__name__)
+
 
 def parse_scm_version(config: Configuration) -> ScmVersion | None:
-    if config.parse is not None:
-        parse_result = config.parse(config.absolute_root, config=config)
-        if parse_result is not None and not isinstance(parse_result, ScmVersion):
-            raise TypeError(
-                f"version parse result was {str!r}\n"
-                "please return a parsed version (ScmVersion)"
-            )
-        return parse_result
-    else:
-        entrypoint = "setuptools_scm.parse_scm"
-        root = config.absolute_root
-        return _entrypoints.version_from_entrypoint(config, entrypoint, root)
+    try:
+        if config.parse is not None:
+            parse_result = config.parse(config.absolute_root, config=config)
+            if parse_result is not None and not isinstance(parse_result, ScmVersion):
+                raise TypeError(
+                    f"version parse result was {str!r}\n"
+                    "please return a parsed version (ScmVersion)"
+                )
+            return parse_result
+        else:
+            entrypoint = "setuptools_scm.parse_scm"
+            root = config.absolute_root
+            return _entrypoints.version_from_entrypoint(config, entrypoint, root)
+    except _run_cmd.CommandNotFoundError as e:
+        _log.exception("command %s not found while parsing the scm, using fallbacks", e)
+        return None
 
 
 def parse_fallback_version(config: Configuration) -> ScmVersion | None:

testing/test_git.py

@@ -94,9 +94,13 @@ def test_root_search_parent_directories(
 
 def test_git_gone(wd: WorkDir, monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setenv("PATH", str(wd.cwd / "not-existing"))
+
+    wd.write("pyproject.toml", "[tool.setuptools_scm]")
     with pytest.raises(CommandNotFoundError, match=r"git"):
         git.parse(wd.cwd, Configuration(), git.DEFAULT_DESCRIBE)
 
+    assert wd.get_version(fallback_version="1.0") == "1.0"
+
 
 @pytest.mark.issue("https://github.com/pypa/setuptools_scm/issues/298")
 @pytest.mark.issue(403)

testing/test_mercurial.py

@@ -56,9 +56,12 @@ def test_archival_to_version(expected: str, data: dict[str, str]) -> None:
 def test_hg_gone(wd: WorkDir, monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setenv("PATH", str(wd.cwd / "not-existing"))
     config = Configuration()
+    wd.write("pyproject.toml", "[tool.setuptools_scm]")
     with pytest.raises(CommandNotFoundError, match=r"hg"):
         parse(wd.cwd, config=config)
 
+    assert wd.get_version(fallback_version="1.0") == "1.0"
+
 
 def test_find_files_stop_at_root_hg(
     wd: WorkDir, monkeypatch: pytest.MonkeyPatch