Invalidate delayed completion if cell changed or lost focus

Author: krassowski

atest/05_Features/Completion.robot

@@ -29,6 +29,22 @@ Works When Kernel Is Idle
     ${content} =    Get Cell Editor Content    1
     Should Contain    ${content}    TabError
 
+Invalidates On Cell Change
+    Enter Cell Editor    1    line=2
+    Press Keys    None    TAB
+    Enter Cell Editor    2
+    # just to increase chances of caching this on CI (which is slow)
+    Sleep    5s
+    Completer Should Not Suggest    test
+
+Invalidates On Focus Loss
+    Enter Cell Editor    1    line=2
+    Press Keys    None    TAB
+    Enter Cell Editor    2
+    # just to increase chances of caching this on CI (which is slow)
+    Sleep    5s
+    Completer Should Not Suggest    test
+
 Uses LSP Completions When Kernel Resoponse Times Out
     Configure JupyterLab Plugin    {"kernelResponseTimeout": 1, "waitForBusyKernel": true}    plugin id=${COMPLETION PLUGIN ID}
     Should Complete While Kernel Is Busy
@@ -87,7 +103,6 @@ Continious Hinting Works
 Autocompletes If Only One Option
     Enter Cell Editor    3    line=1
     Press Keys    None    cle
-    Wait Until Fully Initialized
     # First tab brings up the completer
     Press Keys    None    TAB
     Completer Should Suggest    clear
@@ -99,7 +114,6 @@ Autocompletes If Only One Option
 Does Not Autocomplete If Multiple Options
     Enter Cell Editor    3    line=1
     Press Keys    None    c
-    Wait Until Fully Initialized
     # First tab brings up the completer
     Press Keys    None    TAB
     Completer Should Suggest    copy

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

@@ -618,6 +618,15 @@ export class LSPConnector
     token: CodeEditor.IToken,
     cursor_at_request: CodeEditor.IPosition
   ) {
+    if (!this._editor.hasFocus()) {
+      this.console.debug('Ignoring completion response: the corresponding editor lost focus')
+      return {
+        start: reply.start,
+        end: reply.end,
+        items: []
+      };
+    }
+
     const cursor_now = this._editor.getCursorPosition();
 
     // if the cursor advanced in the same line, the previously retrieved completions may still be useful
@@ -626,6 +635,7 @@ export class LSPConnector
       cursor_at_request.line != cursor_now.line ||
       cursor_now.column < cursor_at_request.column
     ) {
+      this.console.debug('Ignoring completion response: cursor has receded or changed line')
       return {
         start: reply.start,
         end: reply.end,