Backport PR #15898: Fix spurious dedent when opening inspector tooltip (

#15917)

Co-authored-by: Michał Krassowski <5832902+krassowski@users.noreply.github.com>

packages/codemirror/src/commands.ts

@@ -4,6 +4,7 @@
  */
 
 import {
+  indentLess,
   indentMore,
   insertNewlineAndIndent,
   insertTab
@@ -19,6 +20,12 @@ import {
  */
 const CODE_RUNNER_SELECTOR = '[data-jp-code-runner]';
 
+/**
+ * Selector for a widget that can open a tooltip.
+ */
+const TOOLTIP_OPENER_SELECTOR =
+  '.jp-CodeMirrorEditor:not(.jp-mod-has-primary-selection):not(.jp-mod-in-leading-whitespace):not(.jp-mod-completer-active)';
+
 /**
  * CodeMirror commands namespace
  */
@@ -76,4 +83,22 @@ export namespace StateCommands {
     }
     return false;
   }
+
+  /**
+   * Prevent dedenting when launching inspection request (a.k.a tooltip).
+   *
+   * This function should be removed once a better way to prevent default
+   * CodeMirror commands is implemented, as tracked in
+   * https://github.com/jupyterlab/jupyterlab/issues/15897
+   */
+  export function dedentIfNotLaunchingTooltip(target: {
+    dom: HTMLElement;
+    state: EditorState;
+    dispatch: (transaction: Transaction) => void;
+  }): boolean {
+    if (target.dom.closest(TOOLTIP_OPENER_SELECTOR)) {
+      return true;
+    }
+    return indentLess(target);
+  }
 }

packages/codemirror/src/extension.ts

@@ -2,7 +2,7 @@
 // Distributed under the terms of the Modified BSD License.
 
 import { closeBrackets, closeBracketsKeymap } from '@codemirror/autocomplete';
-import { defaultKeymap, indentLess } from '@codemirror/commands';
+import { defaultKeymap } from '@codemirror/commands';
 import {
   bracketMatching,
   foldGutter,
@@ -715,7 +715,7 @@ export namespace EditorExtensionRegistry {
           {
             key: 'Tab',
             run: StateCommands.indentMoreOrInsertTab,
-            shift: indentLess
+            shift: StateCommands.dedentIfNotLaunchingTooltip
           }
         ],
         factory: () =>