Fix duplicate dock band pins by niels9001 · Pull Request #46637 · microsoft/PowerToys

niels9001 · 2026-03-30T19:06:40Z

Summary of the Pull Request

Summary

Dock bands could be pinned multiple times, resulting in duplicate entries in settings and duplicate UI items in the dock.

Root Cause

CommandProviderWrapper.PinDockBand had a TOCTOU (time-of-check-time-of-use) race: the duplicate check read a settings snapshot before entering the UpdateSettings CAS loop. If concurrent or retried calls overlapped, the transform lambda would blindly .Add() without re-checking, producing duplicate entries in DockSettings.StartBands / CenterBands / EndBands.

Additionally, DockViewModel.SetupBands rendered every entry from settings without deduplication, so any duplicates already persisted in settings.json were faithfully displayed.

TeamsExtension didn't set an explicit id
The TeamsExtension was missing a best practice: the dock band's MeetingControlPage had no explicit Id, so CmdPal generated an unstable hash-based ID from the band's title and subtitle. Setting a stable Id makes the band more resilient against CmdPal bugs and ensures pin entries in settings always match the band across title renames or extension updates.

Changes

File	Change
`CommandProviderWrapper.cs`	Moved the duplicate guard inside the `UpdateSettings` lambda so it is re-evaluated on every CAS retry against the latest snapshot
`CommandProviderWrapper.cs`	Added a dedup check in the internal `PinDockBand(TopLevelViewModel)` before appending to `DockBandItems`
`DockViewModel.cs`	Added a `HashSet` in `SetupBands` to skip duplicate `(ProviderId, CommandId)` entries at render time

Validation

Build succeeds (exit code 0)
Verified duplicate entries in settings.json are no longer rendered after the SetupBands dedup
Verified the CAS-lambda guard prevents new duplicates from being written

PR Checklist

Closes: CmdPal Dock: duplicate bands #46638

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

jiripolasek · 2026-03-30T21:10:28Z

/azp run

azure-pipelines · 2026-03-30T21:10:39Z

Azure Pipelines successfully started running 1 pipeline(s).

Copilot

Pull request overview

Fixes an issue in CmdPal Dock where the same dock band could be pinned multiple times (persisting duplicates in settings and rendering duplicate UI items) by making pinning idempotent under concurrent updates and adding UI-time deduplication.

Changes:

Moved the “already pinned” guard into the ISettingsService.UpdateSettings CAS transform to eliminate the TOCTOU window during retries.
Added an in-memory dedup guard when appending to CommandProviderWrapper.DockBandItems.
Added render-time deduplication in DockViewModel.SetupBands to skip duplicate (ProviderId, CommandId) entries from settings.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Dock/DockViewModel.cs	Deduplicates dock band settings entries at render time to avoid duplicate UI items.
src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/CommandProviderWrapper.cs	Makes dock-band pinning safe under CAS retries and avoids duplicate in-memory band entries.

Copilot · 2026-04-01T18:51:00Z

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Dock/DockViewModel.cs

+        HashSet<string> seen = new(StringComparer.Ordinal);
        foreach (var band in bands)
        {
            var commandId = band.CommandId;
+
+            // Skip duplicate entries that share the same provider + command id
+            var key = $"{band.ProviderId}\0{commandId}";
+            if (!seen.Add(key))


Building a composite string key here allocates on every iteration of SetupBands. Since this can run on every settings change / DockBands collection change, consider avoiding the per-item string allocation (e.g., use a HashSet of tuples or a custom comparer over (ProviderId, CommandId)).

Suggested change

HashSet<string> seen = new(StringComparer.Ordinal);

foreach (var band in bands)

{

var commandId = band.CommandId;

// Skip duplicate entries that share the same provider + command id

var key = $"{band.ProviderId}\0{commandId}";

if (!seen.Add(key))

HashSet<(string ProviderId, string CommandId)> seen = new();

foreach (var band in bands)

{

var commandId = band.CommandId;

// Skip duplicate entries that share the same provider + command id

if (!seen.Add((band.ProviderId, commandId)))

Copilot · 2026-04-01T18:51:00Z

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Dock/DockViewModel.cs

+            if (!seen.Add(key))
+            {
+                Logger.LogWarning($"Skipping duplicate dock band entry {commandId} for provider {band.ProviderId}");
+                continue;


Logging a warning for each duplicate entry inside this loop can spam logs if settings.json already contains duplicates (and SetupBands runs repeatedly). Consider downgrading to Debug/Info or aggregating (log once with a count) to keep this path quieter.

Copilot · 2026-04-01T18:51:01Z

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/CommandProviderWrapper.cs

        var bands = this.DockBandItems.ToList();
+
+        // Prevent duplicate entries in the in-memory band list
+        if (bands.Any(b => b.Id == bandVm.Id))
+        {
+            Logger.LogDebug($"Dock band '{bandVm.Id}' already exists in DockBandItems; skipping.");
+            return;
+        }
+


This method materializes DockBandItems into a List before checking for duplicates. If the band is already present, the ToList allocation is wasted; consider checking DockBandItems first and only allocating a List when you actually need to append.

Suggested change

var bands = this.DockBandItems.ToList();

// Prevent duplicate entries in the in-memory band list

if (bands.Any(b => b.Id == bandVm.Id))

{

Logger.LogDebug($"Dock band '{bandVm.Id}' already exists in DockBandItems; skipping.");

return;

}

var existingBands = this.DockBandItems;

// Prevent duplicate entries in the in-memory band list

if (existingBands.Any(b => b.Id == bandVm.Id))

{

Logger.LogDebug($"Dock band '{bandVm.Id}' already exists in DockBandItems; skipping.");

return;

}

var bands = existingBands.ToList();

Copilot · 2026-04-01T18:51:01Z

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/CommandProviderWrapper.cs

+                if (dockSettings.StartBands.Any(b => b.CommandId == commandId && b.ProviderId == this.ProviderId) ||
+                    dockSettings.CenterBands.Any(b => b.CommandId == commandId && b.ProviderId == this.ProviderId) ||
+                    dockSettings.EndBands.Any(b => b.CommandId == commandId && b.ProviderId == this.ProviderId))
+                {
+                    Logger.LogDebug($"Dock band '{commandId}' from provider '{this.ProviderId}' is already pinned; skipping.");
+                    return s;
+                }


Because this CAS lambda can now return the original settings when the band is already pinned, the overall PinDockBand call becomes a no-op in that case — but the method still raises CommandsChanged afterwards (outside this hunk). This can trigger unnecessary reload work/UI churn; consider adding a fast-path pre-check before UpdateSettings (while keeping this in-lambda guard) or otherwise only raising CommandsChanged when a pin was actually added.

jiripolasek · 2026-04-03T14:20:08Z

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/CommandProviderWrapper.cs

        // retrieve the new items.
        this.CommandsChanged?.Invoke(this, args);

    internal void PinDockBand(TopLevelViewModel bandVm)


This is called only from an unused TopLevelCommandManager.PinDockBand (also unused in v0.98.1)

jiripolasek · 2026-04-03T14:23:23Z

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/CommandProviderWrapper.cs

            ShowSubtitles = showSubtitles,
        };

        settingsService.UpdateSettings(


This is not in 0.98.* line (added in 46451) (I mentioned this in relation of merging this to stable as a hotfix 0.98.2)

Deduping

490e489

niels9001 requested a review from zadjii-msft March 30, 2026 19:06

michaeljolley added the Product-Command Palette Refers to the Command Palette utility label Apr 1, 2026

Merge branch 'main' into niels9001/deduping-bands

63bb079

michaeljolley requested a review from Copilot April 1, 2026 18:45

Copilot started reviewing on behalf of michaeljolley April 1, 2026 18:47 View session

Copilot AI reviewed Apr 1, 2026

View reviewed changes

niels9001 requested a review from michaeljolley April 3, 2026 09:24

niels9001 added the 0.98.2 label Apr 3, 2026

niels9001 requested a review from jiripolasek April 3, 2026 09:24

jiripolasek reviewed Apr 3, 2026

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Fix duplicate dock band pins#46637

Fix duplicate dock band pins#46637
niels9001 wants to merge 2 commits intomainfrom
niels9001/deduping-bands

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Summary of the Pull Request

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