fix: debug widget layout updates

Use customized `PanelLayout#removeWidget` and
`PanelLayout#insertWidget` logic for the layout
updates. The customized functions ensure no side
effect if adding/removing the widget to/from the
layout but it's already present/absent.

Unlike the default [`PanelLayout#removeWidget`](9f5e11025b/packages/widgets/src/panellayout.ts (L154-L156))
behavior, do not try to remove the widget if it's
not present (has a negative index). Otherwise,
required widgets might be removed based on the
default [`ArrayExt#removeAt`](9f5e11025b/packages/algorithm/src/array.ts (L1075-L1077))
behavior.

Closes: arduino/arduino-ide#2354

Signed-off-by: Akos Kitta <a.kitta@arduino.cc>

arduino-ide-extension/src/browser/theia/dialogs/widgets.ts

@@ -0,0 +1,51 @@
+import {
+  Layout,
+  PanelLayout,
+  Widget,
+} from '@theia/core/shared/@phosphor/widgets';
+
+/**
+ *
+ * Removes the widget from the layout if the `layout` is a `PanelLayout` and the widget is present in the layout.
+ * Otherwise, it's NOOP
+ * @param layout the layout to remove the widget from. Must be a `PanelLayout`.
+ * @param toRemove the widget to remove from the layout
+ */
+export function removeWidgetIfPresent(
+  layout: Layout | null,
+  toRemove: Widget
+): void {
+  if (layout instanceof PanelLayout) {
+    const index = layout.widgets.indexOf(toRemove);
+    if (index < 0) {
+      // Unlike the default `PanelLayout#removeWidget` behavior, (https://github.com/phosphorjs/phosphor/blob/9f5e11025b62d2c4a6fb59e2681ae1ed323dcde4/packages/widgets/src/panellayout.ts#L154-L156)
+      // do not try to remove widget if it's not present (the index is negative).
+      // Otherwise, required widgets could be removed based on the default ArrayExt behavior (https://github.com/phosphorjs/phosphor/blob/9f5e11025b62d2c4a6fb59e2681ae1ed323dcde4/packages/algorithm/src/array.ts#L1075-L1077)
+      // See https://github.com/arduino/arduino-ide/issues/2354 for more details.
+      return;
+    }
+    layout.removeWidget(toRemove);
+  }
+}
+
+/**
+ *
+ * Inserts the widget to the `0` index of the layout if the `layout` is a `PanelLayout` and the widget is not yet part of the layout.
+ * Otherwise, it's NOOP
+ * @param layout the layout to add the widget to. Must be a `PanelLayout`.
+ * @param toAdd the widget to add to the layout
+ */
+export function unshiftWidgetIfNotPresent(
+  layout: Layout | null,
+  toAdd: Widget
+): void {
+  if (layout instanceof PanelLayout) {
+    const index = layout.widgets.indexOf(toAdd);
+    if (index >= 0) {
+      // Do not try to add the widget to the layout if it's already present.
+      // This is the counterpart logic of the `removeWidgetIfPresent` function.
+      return;
+    }
+    layout.insertWidget(0, toAdd);
+  }
+}