Fix CLI crashing on every invocation when package metadata is missing

osipy/cli/main.py

@@ -30,10 +30,20 @@
 
 
 def _get_version() -> str:
-    """Read version without importing the full osipy package."""
-    from importlib.metadata import version
+    """Read version without importing the full osipy package.
 
-    return version("osipy")
+    Falls back to a placeholder instead of raising when osipy isn't
+    installed with discoverable package metadata (e.g. a source checkout
+    run without ``pip install -e .``). This is called eagerly while
+    building the parser, so a raise here would take down the entire CLI,
+    not just ``--version``.
+    """
+    from importlib.metadata import PackageNotFoundError, version
+
+    try:
+        return version("osipy")
+    except PackageNotFoundError:
+        return "(version unknown)"
 
 
 def create_parser() -> argparse.ArgumentParser:

tests/unit/cli/test_config.py

@@ -26,7 +26,7 @@
     dump_defaults,
     load_config,
 )
-from osipy.cli.main import create_parser
+from osipy.cli.main import _get_version, create_parser
 
 # ---------------------------------------------------------------------------
 # Fixtures
@@ -1114,3 +1114,53 @@ def test_output_override(self) -> None:
 
         args_short = parser.parse_args(["-o", "/out", "config.yaml", "/data"])
         assert args_short.output == "/out"
+
+
+# ---------------------------------------------------------------------------
+# TestVersionLookupRegression — GH-173
+# ---------------------------------------------------------------------------
+
+
+class TestVersionLookupRegression:
+    """create_parser() must never crash when osipy's package metadata isn't
+    discoverable (e.g. a source checkout without `pip install -e .`), since
+    it runs on every CLI invocation, not just `--version`."""
+
+    def test_get_version_falls_back_when_metadata_missing(self, monkeypatch) -> None:
+        """_get_version() returns a placeholder instead of raising."""
+        import importlib.metadata
+
+        def _raise(_name: str) -> str:
+            raise importlib.metadata.PackageNotFoundError("osipy")
+
+        monkeypatch.setattr(importlib.metadata, "version", _raise)
+
+        assert _get_version() == "(version unknown)"
+
+    def test_create_parser_succeeds_when_metadata_missing(self, monkeypatch) -> None:
+        """create_parser() doesn't raise even if package metadata lookup fails."""
+        import importlib.metadata
+
+        def _raise(_name: str) -> str:
+            raise importlib.metadata.PackageNotFoundError("osipy")
+
+        monkeypatch.setattr(importlib.metadata, "version", _raise)
+
+        parser = create_parser()
+        assert parser is not None
+
+    def test_version_flag_exits_cleanly_when_metadata_missing(
+        self, monkeypatch
+    ) -> None:
+        """--version still exits 0 with a fallback string, not a traceback."""
+        import importlib.metadata
+
+        def _raise(_name: str) -> str:
+            raise importlib.metadata.PackageNotFoundError("osipy")
+
+        monkeypatch.setattr(importlib.metadata, "version", _raise)
+
+        parser = create_parser()
+        with pytest.raises(SystemExit) as exc_info:
+            parser.parse_args(["--version"])
+        assert exc_info.value.code == 0