Fail loudly on unreadable config and empty library roots

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

2 files changed, 13 insertions, 0 deletions

diff --git a/generat3d/config.py b/generat3d/config.py
index 9ea7266..804723f 100644
--- a/generat3d/config.py
+++ b/generat3d/config.py
@@ -39,6 +39,8 @@ def library_roots(cli_roots, path=None):
                 data = tomllib.load(f)
         except tomllib.TOMLDecodeError as e:
             raise Error(f"{path}: {e}") from None
+        except OSError as e:
+            raise Error(f"{path}: {e.strerror or e}") from None
         unknown = sorted(set(data) - KEYS)
         if unknown:
             raise Error(f"{path}: unknown keys: {', '.join(unknown)}")
@@ -49,6 +51,8 @@ def library_roots(cli_roots, path=None):
         raise Error(f"no library roots: pass -L or set library_roots in {path}")
     out = []
     for r in roots:
+        if not r.strip():
+            raise Error("empty library root")
         p = Path(r).expanduser()
         if not p.is_dir():
             raise Error(f"library root not found: {p}")
diff --git a/tests/test_config.py b/tests/test_config.py
index d1ad0d2..72ed0f6 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -79,3 +79,12 @@ class ConfigTest(unittest.TestCase):
                 del os.environ["XDG_CONFIG_HOME"]
             else:
                 os.environ["XDG_CONFIG_HOME"] = old
+
+    def test_unreadable_config_is_fatal(self):
+        self.cfg.mkdir()
+        with self.assertRaisesRegex(Error, "config.toml"):
+            library_roots([], self.cfg)
+
+    def test_empty_library_root_is_fatal(self):
+        with self.assertRaisesRegex(Error, "empty library root"):
+            library_roots([""], self.cfg)