Test the completer in FileEditor (& fix related setup issue)

Author: krassowski

atest/05_Features/Completion.robot

@@ -39,6 +39,14 @@ Works When Kernel Is Shut Down
     # this comes from kernel:
     Completer Should Not Suggest    %%timeit
 
+Works In File Editor
+    Prepare File for Editing    Python    completion    completion.py
+    Place Cursor In File Editor At    9    2
+    Capture Page Screenshot    01-editor-ready.png
+    Trigger Completer
+    Completer Should Suggest    add
+    [Teardown]    Clean Up After Working With File    completion.py
+
 Autocompletes If Only One Option
     Enter Cell Editor    3    line=1
     Press Keys    None    cle

atest/Keywords.robot

@@ -263,6 +263,15 @@ Place Cursor In Cell Editor At
     Enter Cell Editor    ${cell_nr}    ${line}
     Execute JavaScript    return document.querySelector('.jp-Cell:nth-child(${cell_nr}) .CodeMirror').CodeMirror.setCursor({line: ${line} - 1, ch: ${character}})
 
+Enter File Editor
+    Click Element    css:.jp-FileEditor .CodeMirror
+    Wait Until Page Contains Element    css:.jp-FileEditor .CodeMirror-focused
+
+Place Cursor In File Editor At
+    [Arguments]    ${line}    ${character}
+    Enter File Editor
+    Execute JavaScript    return document.querySelector('.jp-FileEditor .CodeMirror').CodeMirror.setCursor({line: ${line} - 1, ch: ${character}})
+
 Wait Until Fully Initialized
     Wait Until Element Contains    ${STATUSBAR}    Fully initialized    timeout=60s
 

atest/examples/completion.py

@@ -0,0 +1,9 @@
+addition = ''
+
+
+def add(a: int, b: int):
+    """Adds a and b together"""
+    return a, b
+
+
+ad

packages/jupyterlab-lsp/src/adapters/adapter.ts

@@ -87,6 +87,7 @@ export abstract class WidgetAdapter<T extends IDocumentWidget> {
     EditorAdapter<IVirtualEditor<IEditor>>
   >;
   public adapterConnected: Signal<WidgetAdapter<T>, IDocumentConnectionData>;
+  public isConnected: boolean;
   public connection_manager: DocumentConnectionManager;
   public status_message: StatusMessage;
   protected isDisposed = false;
@@ -117,6 +118,7 @@ export abstract class WidgetAdapter<T extends IDocumentWidget> {
     this.activeEditorChanged = new Signal(this);
     this.adapters = new Map();
     this.status_message = new StatusMessage();
+    this.isConnected = false;
 
     // set up signal connections
     this.widget.context.saveState.connect(this.on_save_state, this);
@@ -268,6 +270,7 @@ export abstract class WidgetAdapter<T extends IDocumentWidget> {
 
     this.connect_adapter(data.virtual_document, data.connection);
     this.adapterConnected.emit(data);
+    this.isConnected = true;
 
     await this.update_documents().then(() => {
       // refresh the document on the LSP server

packages/jupyterlab-lsp/src/features/completion/completion.ts

@@ -85,6 +85,7 @@ export class CompletionLabIntegration implements IFeatureLabIntegration {
     manager: ILSPAdapterManager,
     adapter: WidgetAdapter<IDocumentWidget>
   ) {
+    console.log('ADAPTER CHANGED TO ', adapter);
     if (this.current_adapter) {
       // disconnect signals from the old adapter
       this.current_adapter.activeEditorChanged.disconnect(
@@ -97,13 +98,17 @@ export class CompletionLabIntegration implements IFeatureLabIntegration {
       );
     }
     this.current_adapter = adapter;
+    // connect the new adapter
+    if (this.current_adapter.isConnected) {
+      this.connect_completion(this.current_adapter);
+      this.set_connector(adapter, { editor: adapter.activeEditor });
+    }
     // connect signals to the new adapter
     this.current_adapter.activeEditorChanged.connect(this.set_connector, this);
     this.current_adapter.adapterConnected.connect(
       this.connect_completion,
       this
     );
-    this.set_connector(adapter, { editor: adapter.activeEditor });
   }
 
   connect_completion(