[dotnet-watch] Add device selection support by jonathanpeppers · Pull Request #53631 · dotnet/sdk

jonathanpeppers · 2026-03-30T19:05:51Z

Adds device selection to dotnet-watch for MAUI/mobile scenarios, mirroring the dotnet-run device selection flow from the spec (documentation/specs/dotnet-run-for-maui.md).

Merged TargetFrameworkSelectionPrompt and the new device prompt into a single WatchSelectionPrompt (library) / SpectreWatchSelectionPrompt (console app), keeping Spectre.Console isolated to the console app project.

After TFM selection, HotReloadDotNetWatcher calls the ComputeAvailableDevices MSBuild target via in-process MSBuild. A single device is auto-selected; multiple devices show an interactive Spectre prompt with search. The selected device and its RuntimeIdentifier are passed to dotnet build (-p:Device, -p:RuntimeIdentifier) and to the launched dotnet run subprocess (--device). A re-restore is performed when the device provides a RuntimeIdentifier not present in the original restore.

Adds --device CLI option to dotnet-watch for pre-specifying a device.

Tests:

Unit tests for prompt selection, search, caching, and FormatDevice
E2E tests using DotnetRunDevices test asset: interactive device selection, single-device auto-select

Adds device selection to dotnet-watch for MAUI/mobile scenarios, mirroring the dotnet-run device selection flow from the spec (documentation/specs/dotnet-run-for-maui.md). Merged TargetFrameworkSelectionPrompt and the new device prompt into a single WatchSelectionPrompt (library) / SpectreWatchSelectionPrompt (console app), keeping Spectre.Console isolated to the console app project and avoiding a second constructor parameter on HotReloadDotNetWatcher. After TFM selection, HotReloadDotNetWatcher calls the ComputeAvailableDevices MSBuild target via in-process MSBuild. A single device is auto-selected; multiple devices show an interactive Spectre prompt with search. The selected device and its RuntimeIdentifier are passed to dotnet build (-p:Device, -p:RuntimeIdentifier) and to the launched dotnet run subprocess (--device). A re-restore is performed when the device provides a RuntimeIdentifier not present in the original restore. Adds --device CLI option to dotnet-watch for pre-specifying a device. Tests: - Unit tests for prompt selection, search, caching, and FormatDevice - E2e tests using DotnetRunDevices test asset: interactive device selection, single-device auto-select Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Adds MAUI/mobile-oriented device selection to dotnet-watch Hot Reload, aligning the watch experience with the dotnet run device-selection spec by computing devices via MSBuild and prompting (when needed) through a Spectre.Console-based UI.

Changes:

Introduces a unified selection prompt abstraction (WatchSelectionPrompt) for both target framework and device selection, with a Spectre.Console implementation for interactive console scenarios.
Extends HotReloadDotNetWatcher to invoke ComputeAvailableDevices, auto-select a single device, prompt when multiple devices are available, and flow device/RID into build + run.
Adds --device to dotnet-watch, updates resources/localization, and adds unit + E2E coverage for device selection prompting/formatting.

Reviewed changes

Copilot reviewed 32 out of 32 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
test/dotnet-watch.Tests/TestUtilities/NoOpWatchSelectionPrompt.cs	Adds a non-interactive prompt implementation for tests.
test/dotnet-watch.Tests/TestUtilities/DotNetWatchTestBase.cs	Updates watcher construction to use `WatchSelectionPrompt`.
test/dotnet-watch.Tests/HotReload/WatchSelectionPromptTests.cs	New unit tests covering framework/device selection, search, caching, and device formatting.
test/dotnet-watch.Tests/HotReload/TargetFrameworkSelectionPromptTests.cs	Removes old prompt-specific tests after prompt unification.
test/dotnet-watch.Tests/HotReload/MauiHotReloadTests.cs	Adds E2E tests for interactive device selection and single-device auto-select.
test/dotnet-watch.Tests/HotReload/BuildProjectsTests.cs	Updates tests for new watcher signature and new `deviceSelector` parameter.
src/Dotnet.Watch/Watch/UI/WatchSelectionPrompt.cs	New shared abstraction for framework + device selection with cached selections.
src/Dotnet.Watch/Watch/UI/TargetFrameworkSelectionPrompt.cs	Removes superseded framework-only prompt abstraction.
src/Dotnet.Watch/Watch/UI/IReporter.cs	Adds a new message descriptor related to device availability.
src/Dotnet.Watch/Watch/UI/DeviceInfo.cs	Adds a record representing device metadata coming from MSBuild.
src/Dotnet.Watch/Watch/Process/ProjectLauncher.cs	Passes selected device/RID into the launched `dotnet run` invocation.
src/Dotnet.Watch/Watch/HotReload/HotReloadDotNetWatcher.cs	Implements MSBuild-driven device discovery/selection and flows results into build pipeline.
src/Dotnet.Watch/Watch/Context/ProjectOptions.cs	Adds `Device` and `DeviceRuntimeIdentifier` to project launch/build options.
src/Dotnet.Watch/dotnet-watch/xlf/Resources.zh-Hant.xlf	Localization updates for new device-related strings.
src/Dotnet.Watch/dotnet-watch/xlf/Resources.zh-Hans.xlf	Localization updates for new device-related strings.
src/Dotnet.Watch/dotnet-watch/xlf/Resources.tr.xlf	Localization updates for new device-related strings.
src/Dotnet.Watch/dotnet-watch/xlf/Resources.ru.xlf	Localization updates for new device-related strings.
src/Dotnet.Watch/dotnet-watch/xlf/Resources.pt-BR.xlf	Localization updates for new device-related strings.
src/Dotnet.Watch/dotnet-watch/xlf/Resources.pl.xlf	Localization updates for new device-related strings.
src/Dotnet.Watch/dotnet-watch/xlf/Resources.ko.xlf	Localization updates for new device-related strings.
src/Dotnet.Watch/dotnet-watch/xlf/Resources.ja.xlf	Localization updates for new device-related strings.
src/Dotnet.Watch/dotnet-watch/xlf/Resources.it.xlf	Localization updates for new device-related strings.
src/Dotnet.Watch/dotnet-watch/xlf/Resources.fr.xlf	Localization updates for new device-related strings.
src/Dotnet.Watch/dotnet-watch/xlf/Resources.es.xlf	Localization updates for new device-related strings.
src/Dotnet.Watch/dotnet-watch/xlf/Resources.de.xlf	Localization updates for new device-related strings.
src/Dotnet.Watch/dotnet-watch/xlf/Resources.cs.xlf	Localization updates for new device-related strings.
src/Dotnet.Watch/dotnet-watch/Watch/BuildEvaluator.cs	Ensures `--device` is included in the evaluated run arguments.
src/Dotnet.Watch/dotnet-watch/UI/SpectreWatchSelectionPrompt.cs	Implements interactive Spectre prompt for framework + device selection.
src/Dotnet.Watch/dotnet-watch/Resources.resx	Adds new device prompt/help strings.
src/Dotnet.Watch/dotnet-watch/Program.cs	Switches to the unified selection prompt for Hot Reload runs.
src/Dotnet.Watch/dotnet-watch/CommandLine/DotnetWatchCommandDefinition.cs	Adds the `--device` root option to `dotnet-watch`.
src/Dotnet.Watch/dotnet-watch/CommandLine/CommandLineOptions.cs	Parses `--device` into `CommandLineOptions` and flows into `ProjectOptions`.

Copilot · 2026-03-30T19:12:26Z

src/Dotnet.Watch/Watch/HotReload/HotReloadDotNetWatcher.cs

+            var needsFrameworkSelection = targetFramework == null && frameworkSelector != null;
+            var needsDeviceSelection = mainProjectOptions?.Device == null && deviceSelector != null;
+
            if (mainProjectOptions == null ||
-                frameworkSelector == null ||
-                targetFramework != null ||
+                (!needsFrameworkSelection && !needsDeviceSelection) ||
                !mainProjectOptions.Representation.IsProjectFile)


When --device is specified on the command line, mainProjectOptions.Device is non-null so device computation/selection is skipped and selectedDevice remains null. As a result, the subsequent build/restore invocations won’t get -p:Device=... (and no RID discovery/re-restore can happen), which breaks the intended “pre-specified device” flow. Consider treating an explicitly provided device as a pre-selection: run ComputeAvailableDevices to validate/resolve the matching device (including RuntimeIdentifier), set selectedDevice, and pass it into the build/restore path (including the re-restore when the RID is new).

That is one thing we don't do for dotnet run either. If someone passes --device, we just use it and don't compute the RuntimeIdentifier.

I think it is OK for now; we haven't found a place you would need this -- you can pass -r.

src/Dotnet.Watch/Watch/HotReload/HotReloadDotNetWatcher.cs

src/Dotnet.Watch/dotnet-watch/CommandLine/CommandLineOptions.cs

src/Dotnet.Watch/dotnet-watch/Watch/BuildEvaluator.cs

- Fix Aspire build: update HotReloadDotNetWatcher constructor call - Make WatchSelectionPrompt nullable; Aspire and tests pass null - Remove NoPromptWatchSelectionPrompt and NoOpWatchSelectionPrompt - Zero devices now propagates failure instead of silently continuing - Fix stale XML doc on TrySelectDeviceAsync Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/Dotnet.Watch/Watch/UI/WatchSelectionPrompt.cs

src/Dotnet.Watch/Watch/HotReload/HotReloadDotNetWatcher.cs

- Rename WatchSelectionPrompt to BuildParametersSelectionPrompt - Use needsFrameworkSelection/needsDeviceSelection variables in selection blocks - Use LoadedProjectGraph.TryGetProjectNode + DeepCopy instead of creating a new ProjectInstance - Use ProjectBuildManager for building ComputeAvailableDevices target - Move ComputeAvailableDevices constant to TargetNames Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Mirror the targetFramework pattern: selectedDevice and selectedDeviceRuntimeIdentifier are now string? variables initialized from CLI options, making needsDeviceSelection consistent with needsFrameworkSelection. BuildProjectsResult carries string? fields instead of DeviceInfo?. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Use the proper CLI option for passing RuntimeIdentifier to build, restore, and run subprocesses. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/Dotnet.Watch/Watch/HotReload/HotReloadDotNetWatcher.cs

Inline the null checks from needsFrameworkSelection/needsDeviceSelection directly into the if conditions so the compiler can see the narrowing without needing is not null guards or ! operators. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

jonathanpeppers requested review from a team and tmat as code owners March 30, 2026 19:05

Copilot AI review requested due to automatic review settings March 30, 2026 19:05

Copilot started reviewing on behalf of jonathanpeppers March 30, 2026 19:06 View session

Copilot AI reviewed Mar 30, 2026

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tmat reviewed Mar 30, 2026

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Add BuildManager to LoadedProjectGraph

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jonathanpeppers and others added 5 commits March 31, 2026 16:00

Use --runtime instead of -p:RuntimeIdentifier

89fd8dd

Use the proper CLI option for passing RuntimeIdentifier to build, restore, and run subprocesses. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Fix whitespace changes

6b2ed2d

Use var

1d7e347

jonathanpeppers requested a review from tmat March 31, 2026 21:31

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[dotnet-watch] Add device selection support#53631

[dotnet-watch] Add device selection support#53631
jonathanpeppers wants to merge 9 commits intorelease/10.0.3xxfrom
dev/peppers/dotnet-watch-device-selection

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