Delay creation of .virtual_documents until actually needed

because deployments may primarily use a well-behaved
server that does not need virtual documents folder
together with secondary servers that do require it
but are only used from time to time when opening
specific file types.

This can also marginally improve startup times as there is no
need to wait on file system operation of purging the directory
which is now only done on first relevant LSP message.

Author: krassowski

python_packages/jupyter_lsp/jupyter_lsp/serverextension.py

@@ -29,10 +29,15 @@ async def initialize(nbapp, virtual_documents_uri):  # pragma: no cover
 
     if any(servers_requiring_disk_access):
         nbapp.log.debug(
-            "[lsp] servers that requested virtual documents on disk: %s",
+            "[lsp] Servers that requested virtual documents on disk: %s",
             servers_requiring_disk_access,
         )
         setup_shadow_filesystem(virtual_documents_uri=virtual_documents_uri)
+    else:
+        nbapp.log.debug(
+            "[lsp] None of the installed servers require virtual documents"
+            " disabling shadow filesystem."
+        )
 
     nbapp.log.debug(
         "[lsp] The following Language Servers will be available: {}".format(

python_packages/jupyter_lsp/jupyter_lsp/tests/test_virtual_documents_shadow.py

@@ -120,20 +120,44 @@ async def test_shadow(shadow_path, message_func, content, expected_content, mana
 
 
 @pytest.mark.asyncio
-async def test_short_circuits_for_well_behaved_server(
+async def test_no_shadow_for_well_behaved_server(
     shadow_path,
 ):
     """We call server well behaved when it does not require a disk copy"""
-    shadow = setup_shadow_filesystem(Path(shadow_path).as_uri())
-    ok_file_path = Path(shadow_path) / "test.py"
+    shadow_path_for_well = Path(shadow_path) / "well"
+    shadow = setup_shadow_filesystem(Path(shadow_path_for_well).as_uri())
+    ok_file_path = Path(shadow_path_for_well) / "test.py"
 
     manager = SimpleNamespace(
         language_servers={"python-lsp-server": {"requires_documents_on_disk": False}}
     )
 
     message = did_open(ok_file_path.as_uri(), "content\nof\nopened\nfile")
     result = await shadow("client", message, "python-lsp-server", manager)
+    # should short-circuit for well behaved server
     assert result is None
+    # should not create the directory
+    assert not shadow_path_for_well.exists()
+
+
+@pytest.mark.asyncio
+async def test_shadow_created_for_ill_behaved_server(
+    shadow_path,
+):
+    shadow_path_for_ill = Path(shadow_path) / "ill"
+    shadow = setup_shadow_filesystem(shadow_path_for_ill.as_uri())
+    ok_file_path = Path(shadow_path_for_ill) / "test.py"
+
+    manager = SimpleNamespace(
+        language_servers={"python-lsp-server": {"requires_documents_on_disk": True}}
+    )
+
+    message = did_open(ok_file_path.as_uri(), "content\nof\nopened\nfile")
+    result = await shadow("client", message, "python-lsp-server", manager)
+    assert result is not None
+    # should create the directory at given path
+    assert shadow_path_for_ill.exists()
+    assert shadow_path_for_ill.is_dir()
 
 
 @pytest.mark.asyncio

python_packages/jupyter_lsp/jupyter_lsp/virtual_documents_shadow.py

@@ -110,13 +110,8 @@ def setup_shadow_filesystem(virtual_documents_uri: str):
             + virtual_documents_uri
         )
 
+    initialized = False
     shadow_filesystem = Path(file_uri_to_path(virtual_documents_uri))
-    # create if does no exist (so that removal does not raise)
-    shadow_filesystem.mkdir(parents=True, exist_ok=True)
-    # remove with contents
-    rmtree(str(shadow_filesystem))
-    # create again
-    shadow_filesystem.mkdir(parents=True, exist_ok=True)
 
     @lsp_message_listener("client")
     async def shadow_virtual_documents(scope, message, language_server, manager):
@@ -125,6 +120,7 @@ async def shadow_virtual_documents(scope, message, language_server, manager):
         Only create the shadow file if the URI matches the virtual documents URI.
         Returns the path on filesystem where the content was stored.
         """
+        nonlocal initialized
 
         # short-circut if language server does not require documents on disk
         server_spec = manager.language_servers[language_server]
@@ -147,6 +143,16 @@ async def shadow_virtual_documents(scope, message, language_server, manager):
         if not uri.startswith(virtual_documents_uri):
             return
 
+        # initialization (/any file system operations) delayed until needed
+        if not initialized:
+            # create if does no exist (so that removal does not raise)
+            shadow_filesystem.mkdir(parents=True, exist_ok=True)
+            # remove with contents
+            rmtree(str(shadow_filesystem))
+            # create again
+            shadow_filesystem.mkdir(parents=True, exist_ok=True)
+            initialized = True
+
         path = file_uri_to_path(uri)
         editable_file = EditableFile(path)