Fix PythonSpec raising error when module is not installed

Author: krassowski

python_packages/jupyter_lsp/jupyter_lsp/specs/utils.py

@@ -93,6 +93,9 @@ class PythonModuleSpec(SpecBase):
     def __call__(self, mgr: LanguageServerManagerAPI) -> KeyedLanguageServerSpecs:
         spec = __import__("importlib").util.find_spec(self.python_module)
 
+        if not spec:
+            return {}
+
         if not spec.origin:  # pragma: no cover
             return {}
 

python_packages/jupyter_lsp/jupyter_lsp/tests/test_detect.py

@@ -1,6 +1,7 @@
 import shutil
 
 from jupyter_lsp.specs.r_languageserver import RLanguageServer
+from jupyter_lsp.specs.utils import PythonModuleSpec
 
 
 def test_no_detect(manager):
@@ -28,3 +29,23 @@ class NonInstalledRServer(RLanguageServer):
 
     non_installed_server = NonInstalledRServer()
     assert non_installed_server.is_installed(cmd=existing_runner) is False
+
+
+def test_missing_python_module_spec():
+    """Prevent failure in module detection raising error:
+
+    Failed to fetch commands from language server spec finder`python-language-server`:
+        'NoneType' object has no attribute 'origin'
+    Traceback (most recent call last):
+      File "../lib/python3.8/site-packages/jupyter_lsp/manager.py", line 209, in _autodetect_language_servers
+        specs = spec_finder(self)
+      File "../lib/python3.8/site-packages/jupyter_lsp/specs/utils.py", line 96, in __call__
+        if not spec.origin:  # pragma: no cover
+    AttributeError: 'NoneType' object has no attribute 'origin'
+    """
+
+    class NonInstalledPythonServer(PythonModuleSpec):
+        python_module = "not_installed_python_module"
+
+    not_installed_server = NonInstalledPythonServer()
+    assert not_installed_server(mgr=None) == {}