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CmdPal: Null pattern matching based on is expression rather than overridable operators (#40972)

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What the title says. 😄 

Rather than relying on the potentially overloaded `!=` or `==` operators
when checking for null, now we'll use the `is` expression (possibly
combined with the `not` operator) to ensure correct checking. Probably
overkill for many of these classes, but decided to err on the side of
consistency. Would matter more on classes that may be inherited or
extended.

Using `is` and `is not` will provide us a guarantee that no
user-overloaded equality operators (`==`/`!=`) is invoked when a
`expression is null` is evaluated.

In code form, changed all instances of:

```c#
something != null

something == null
```

to:

```c#
something is not null

something is null
```

The one exception was checking null on a `KeyChord`. `KeyChord` is a
struct which is never null so VS will raise an error when trying this
versus just providing a warning when using `keyChord != null`. In
reality, we shouldn't do this check because it can't ever be null. In
the case of a `KeyChord` it **would** be a `KeyChord` equivalent to:

```c#
KeyChord keyChord = new ()
{
    Modifiers = 0,
    Vkey = 0,
    ScanCode = 0
};
```
This commit is contained in:
Michael Jolley
2025-08-18 06:07:28 -05:00
committed by GitHub
parent efb48aa163
commit 6acb793184
138 changed files with 395 additions and 431 deletions
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18
src/modules/cmdpal/Microsoft.CmdPal.UI/ExtViews/ListPage.xaml.cs
View File

@@ -74,7 +74,7 @@ public sealed partial class ListPage : Page,
WeakReferenceMessenger.Default.Unregister<ActivateSelectedListItemMessage>(this);
WeakReferenceMessenger.Default.Unregister<ActivateSecondaryCommandMessage>(this);
if (ViewModel != null)
if (ViewModel is not null)
{
ViewModel.PropertyChanged -= ViewModel_PropertyChanged;
ViewModel.ItemsUpdated -= Page_ItemsUpdated;
@@ -142,13 +142,13 @@ public sealed partial class ListPage : Page,
// here, then in Page_ItemsUpdated trying to select that cached item if
// it's in the list (otherwise, clear the cache), but that seems
// aggressively BODGY for something that mostly just works today.
if (ItemsList.SelectedItem != null)
if (ItemsList.SelectedItem is not null)
{
ItemsList.ScrollIntoView(ItemsList.SelectedItem);
// Automation notification for screen readers
var listViewPeer = Microsoft.UI.Xaml.Automation.Peers.ListViewAutomationPeer.CreatePeerForElement(ItemsList);
if (listViewPeer != null && li != null)
if (listViewPeer is not null && li is not null)
{
var notificationText = li.Title;
listViewPeer.RaiseNotificationEvent(
@@ -165,7 +165,7 @@ public sealed partial class ListPage : Page,
// Find the ScrollViewer in the ListView
var listViewScrollViewer = FindScrollViewer(this.ItemsList);
if (listViewScrollViewer != null)
if (listViewScrollViewer is not null)
{
listViewScrollViewer.ViewChanged += ListViewScrollViewer_ViewChanged;
}
@@ -174,7 +174,7 @@ public sealed partial class ListPage : Page,
private void ListViewScrollViewer_ViewChanged(object? sender, ScrollViewerViewChangedEventArgs e)
{
var scrollView = sender as ScrollViewer;
if (scrollView == null)
if (scrollView is null)
{
return;
}
@@ -256,7 +256,7 @@ public sealed partial class ListPage : Page,
page.PropertyChanged += @this.ViewModel_PropertyChanged;
page.ItemsUpdated += @this.Page_ItemsUpdated;
}
else if (e.NewValue == null)
else if (e.NewValue is null)
{
Logger.LogDebug("cleared view model");
}
@@ -274,7 +274,7 @@ public sealed partial class ListPage : Page,
// ItemsList_SelectionChanged again to give us another chance to change
// the selection from null -> something. Better to just update the
// selection once, at the end of all the updating.
if (ItemsList.SelectedItem == null)
if (ItemsList.SelectedItem is null)
{
ItemsList.SelectedIndex = 0;
}
@@ -307,7 +307,7 @@ public sealed partial class ListPage : Page,
{
var child = VisualTreeHelper.GetChild(parent, i);
var result = FindScrollViewer(child);
if (result != null)
if (result is not null)
{
return result;
}
@@ -329,7 +329,7 @@ public sealed partial class ListPage : Page,
_ => (null, null),
};
if (item == null || element == null)
if (item is null || element is null)
{
return;
}