fix(rust): preserve nested optional import failures

litellm-rust/crates/python-bridge/src/python_settings.rs

@@ -45,8 +45,13 @@ impl PythonSettings {
     pub(crate) fn read_or_unset(self, py: Python<'_>) -> PyResult<Option<Snapshot<'_>>> {
         match self.read(py) {
             Ok(snapshot) => Ok(Some(snapshot)),
-            Err(error) if error.is_instance_of::<PyModuleNotFoundError>(py) => Ok(None),
-            Err(error) => Err(error),
+            Err(error) => {
+                if missing_module(py, &error, "litellm")? {
+                    Ok(None)
+                } else {
+                    Err(error)
+                }
+            }
         }
     }
 
@@ -56,9 +61,24 @@ impl PythonSettings {
     }
 }
 
+fn missing_module(py: Python<'_>, error: &PyErr, expected: &str) -> PyResult<bool> {
+    if !error.is_instance_of::<PyModuleNotFoundError>(py) {
+        return Ok(false);
+    }
+    Ok(error
+        .value(py)
+        .getattr("name")?
+        .extract::<Option<String>>()?
+        .is_some_and(|name| name == expected))
+}
+
 #[cfg(test)]
 mod tests {
-    use pyo3::{exceptions::PyRuntimeError, prelude::*, types::PyDict};
+    use pyo3::{
+        exceptions::{PyImportError, PyModuleNotFoundError, PyRuntimeError},
+        prelude::*,
+        types::PyDict,
+    };
 
     use super::PythonSettings;
     use crate::coercion::FieldSpec;
@@ -150,4 +170,153 @@ values = (Descriptor(), SimpleNamespace(flag=Truth()))
             );
         });
     }
+
+    #[test]
+    fn read_or_unset_returns_none_when_litellm_is_missing() {
+        Python::initialize();
+        Python::attach(|py| {
+            let locals = PyDict::new(py);
+            py.run(
+                c"
+import sys
+class MissingLitellm:
+    def find_spec(self, fullname, path=None, target=None):
+        if fullname == 'litellm':
+            raise ModuleNotFoundError('No module named litellm', name='litellm')
+finder = MissingLitellm()
+previous_litellm = sys.modules.get('litellm')
+had_litellm = 'litellm' in sys.modules
+sys.meta_path.insert(0, finder)
+sys.modules.pop('litellm', None)
+",
+                Some(&locals),
+                Some(&locals),
+            )
+            .unwrap();
+            let result = PythonSettings::Http.read_or_unset(py);
+            assert!(result.unwrap().is_none());
+            py.run(
+                c"
+sys.meta_path.remove(finder)
+if had_litellm:
+    sys.modules['litellm'] = previous_litellm
+else:
+    sys.modules.pop('litellm', None)
+",
+                Some(&locals),
+                Some(&locals),
+            )
+            .unwrap();
+        });
+    }
+
+    #[test]
+    fn read_or_unset_propagates_nested_module_not_found_errors() {
+        Python::initialize();
+        Python::attach(|py| {
+            let locals = PyDict::new(py);
+            py.run(
+                c"
+import sys
+import types
+previous_modules = {
+    name: sys.modules[name]
+    for name in ('litellm', 'litellm.rust_bridge', 'litellm.rust_bridge.settings')
+    if name in sys.modules
+}
+litellm = types.ModuleType('litellm')
+litellm.__path__ = []
+rust_bridge = types.ModuleType('litellm.rust_bridge')
+rust_bridge.__path__ = []
+settings = types.ModuleType('litellm.rust_bridge.settings')
+def http_settings():
+    raise ModuleNotFoundError('No module named certifi', name='certifi')
+settings.http_settings = http_settings
+litellm.rust_bridge = rust_bridge
+rust_bridge.settings = settings
+sys.modules['litellm'] = litellm
+sys.modules['litellm.rust_bridge'] = rust_bridge
+sys.modules['litellm.rust_bridge.settings'] = settings
+",
+                Some(&locals),
+                Some(&locals),
+            )
+            .unwrap();
+            let error = match PythonSettings::Http.read_or_unset(py) {
+                Ok(_) => panic!("nested module errors must propagate"),
+                Err(error) => error,
+            };
+            assert!(error.is_instance_of::<PyModuleNotFoundError>(py));
+            assert_eq!(
+                error
+                    .value(py)
+                    .getattr("name")
+                    .unwrap()
+                    .extract::<String>()
+                    .unwrap(),
+                "certifi"
+            );
+            py.run(
+                c"
+for name in ('litellm.rust_bridge.settings', 'litellm.rust_bridge', 'litellm'):
+    sys.modules.pop(name, None)
+sys.modules.update(previous_modules)
+",
+                Some(&locals),
+                Some(&locals),
+            )
+            .unwrap();
+        });
+    }
+
+    #[test]
+    fn read_or_unset_propagates_import_errors() {
+        Python::initialize();
+        Python::attach(|py| {
+            let locals = PyDict::new(py);
+            py.run(
+                c"
+import sys
+import types
+previous_modules = {
+    name: sys.modules[name]
+    for name in ('litellm', 'litellm.rust_bridge', 'litellm.rust_bridge.settings')
+    if name in sys.modules
+}
+litellm = types.ModuleType('litellm')
+litellm.__path__ = []
+rust_bridge = types.ModuleType('litellm.rust_bridge')
+rust_bridge.__path__ = []
+settings = types.ModuleType('litellm.rust_bridge.settings')
+def http_settings():
+    raise ImportError('cannot import name setting')
+settings.http_settings = http_settings
+litellm.rust_bridge = rust_bridge
+rust_bridge.settings = settings
+sys.modules['litellm'] = litellm
+sys.modules['litellm.rust_bridge'] = rust_bridge
+sys.modules['litellm.rust_bridge.settings'] = settings
+",
+                Some(&locals),
+                Some(&locals),
+            )
+            .unwrap();
+            let error = match PythonSettings::Http.read_or_unset(py) {
+                Ok(_) => panic!("import errors must propagate"),
+                Err(error) => error,
+            };
+            assert!(error.is_instance_of::<PyImportError>(py));
+            assert_eq!(error.to_string(), "ImportError: cannot import name setting");
+            py.run(
+                c"
+for name in ('litellm.rust_bridge.settings', 'litellm.rust_bridge', 'litellm'):
+    sys.modules.pop(name, None)
+sys.modules.update(previous_modules)
+",
+                Some(&locals),
+                Some(&locals),
+            )
+            .unwrap();
+        });
+    }
 }