Implements target framework selection for multi-targeted projects

[tmat]

Change command line parsing to treat --framework option as watch-specific option, not auto-forwarded to a subcommand or build. Forward the option explicitly when invoking the subcommand/build.

Refactor BuildProjectsAsync to allow for target framework detection. If --framework is not specified, we do not know whether a project is multi-targeting until we load it. We can only load it correctly after it's been restored. We do not want to load it multiple times.

Therefore, split the build to 3 steps:

1. dotnet restore on project graph roots,
2. load the project graph,
3. select target framework if the project multi-targets,
4. dotnet build --no-restore on project graph roots.

Add TargetFrameworkSelectionPrompt, which implements a simple framework selection TUI. This will be replaced in future with more sophisticated UI used by dotnet run.

Update all operations (except for restore) on a project graph to ignore outer-build project nodes. Only work with instances with TargetFramework set.

For multi-targeted root projects only consider instances with TargetFramework that matches the framework given on command line via --framework option, or manually selected.

Include project display name in rude edit messages.

[tmat]

@DustinCampbell @jonathanpeppers ptal

[Copilot]

Pull request overview

This PR updates dotnet watch to handle target framework selection for multi-targeted projects by treating --framework/-f as a watch-specific option (not auto-forwarded), explicitly forwarding it when invoking restore/build/run, and prompting interactively when needed after restore/project-graph load.

Changes:

• Reworked watch/build pipeline to restore first, then load the project graph to detect multi-targeting and select a TFM, then build with --no-restore.
• Added a simple interactive target framework selection prompt and updated console input handling to support numeric selection.
• Updated Hot Reload/logging behavior to operate on inner-build project nodes (TFM-specific instances) and include project display names in diagnostics.

Reviewed changes

Copilot reviewed 42 out of 42 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
test/dotnet-watch.Tests/Watch/NoRestoreTests.cs	Updates assertions to expect explicit --framework forwarding.
test/dotnet-watch.Tests/Watch/BuildEvaluatorTests.cs	Adjusts context setup for removal of context-level TargetFramework.
test/dotnet-watch.Tests/TestUtilities/TestProcessRunner.cs	Allows falling back to base runner if no custom impl is provided.
test/dotnet-watch.Tests/TestUtilities/TestOptions.cs	Updates ProjectRepresentation creation to handle --file scenarios.
test/dotnet-watch.Tests/TestUtilities/TestConsole.cs	Adds queued key support to avoid prompt/keypress race in tests.
test/dotnet-watch.Tests/HotReload/TargetFrameworkSelectionPromptTests.cs	New tests for framework selection prompt state/behavior.
test/dotnet-watch.Tests/HotReload/SourceFileUpdateTests.cs	Updates expected message when build fails.
test/dotnet-watch.Tests/HotReload/SourceFileUpdateTests.HotReloadNotSupported.cs	Updates output expectations to include project display prefix.
test/dotnet-watch.Tests/HotReload/RuntimeProcessLauncherTests.cs	Switches trigger to new “runtime launcher created” notification.
test/dotnet-watch.Tests/HotReload/ProjectUpdateTests.cs	Updates output expectations to include project display prefix.
test/dotnet-watch.Tests/HotReload/MauiHotReloadTests.cs	Adds coverage for interactive TFM selection behavior and verifies only selected TFM is built.
test/dotnet-watch.Tests/HotReload/CompilationHandlerTests.cs	Updates ProjectGraphFactory parameter naming and context changes.
test/dotnet-watch.Tests/HotReload/BuildProjectsTests.cs	Refactors tests to validate restore/build sequencing and TFM selection.
test/dotnet-watch.Tests/HotReload/AutoRestartTests.cs	Updates assertions for project display prefixes and message descriptors.
test/dotnet-watch.Tests/HotReload/AspireHotReloadTests.cs	Updates assertions for project display prefixes in Aspire scenarios.
test/dotnet-watch.Tests/CommandLine/LaunchSettingsTests.cs	Runs iteration env-var test in both Hot Reload and non-HR modes.
test/dotnet-watch.Tests/CommandLine/CommandLineOptionsTests.cs	Updates expected forwarding behavior (no longer forwarding --framework as a property).
test/dotnet-watch.Tests/Build/ProjectGraphFactoryTests.cs	Updates ProjectGraphFactory parameter naming.
test/dotnet-watch.Tests/Browser/BrowserTests.cs	Updates rude-edit diagnostic expectations to include project display prefix.
src/Dotnet.Watch/dotnet-watch/Watch/StaticFileHandler.cs	Switches to graph helper API for resolving project nodes.
src/Dotnet.Watch/dotnet-watch/Watch/BuildEvaluator.cs	Explicitly injects --framework into subcommand invocation args.
src/Dotnet.Watch/dotnet-watch/Program.cs	Removes context-level TargetFramework assignment.
src/Dotnet.Watch/dotnet-watch/CommandLine/DotnetWatchCommandDefinition.cs	Adds watch-level --framework/-f option and updates watch-option classification.
src/Dotnet.Watch/dotnet-watch/CommandLine/CommandLineOptions.cs	Stops auto-forwarding --framework; plumbs it into ProjectOptions.TargetFramework.
src/Dotnet.Watch/Watch/UI/TargetFrameworkSelectionPrompt.cs	New prompt component to select a TFM interactively.
src/Dotnet.Watch/Watch/UI/RestartPrompt.cs	Updates input handling to consume ConsoleKeyInfo.
src/Dotnet.Watch/Watch/UI/PhysicalConsole.cs	Adds numeric key mapping for prompt input.
src/Dotnet.Watch/Watch/UI/IReporter.cs	Adds new message descriptors/events and adjusts diagnostic formatting.
src/Dotnet.Watch/Watch/UI/ConsoleInputReader.cs	Returns ConsoleKeyInfo to preserve key char and modifiers.
src/Dotnet.Watch/Watch/Process/RunningProject.cs	Exposes running project TFM via helper method.
src/Dotnet.Watch/Watch/Process/ProjectLauncher.cs	Explicitly forwards --framework to the launched command.
src/Dotnet.Watch/Watch/HotReload/HotReloadDotNetWatcher.cs	Major refactor: restore->graph load->TFM select->build; updated evaluation/rebuild flow.
src/Dotnet.Watch/Watch/HotReload/CompilationHandler.cs	Associates rude-edit diagnostics with project display and updates running-project mapping.
src/Dotnet.Watch/Watch/Context/ProjectOptions.cs	Adds TargetFramework to per-project launch options.
src/Dotnet.Watch/Watch/Context/DotNetWatchContext.cs	Removes context-level TargetFramework in favor of per-project option.
src/Dotnet.Watch/Watch/Build/ProjectGraphUtilities.cs	Adds graph-node helpers and excludes outer-build nodes in traversal.
src/Dotnet.Watch/Watch/Build/ProjectGraphFactory.cs	Renames parameter for virtual-project TFM; adds graph load timing log.
src/Dotnet.Watch/Watch/Build/LoadedProjectGraph.cs	Stores only inner-build nodes and exposes build-file set.
src/Dotnet.Watch/Watch/Build/EvaluationResult.cs	Adjusts evaluation API to accept a pre-loaded graph and filter by selected root TFM.
src/Dotnet.Watch/Watch.Aspire/Server/AspireWatcherLauncher.cs	Removes context-level TargetFramework wiring.
src/Dotnet.Watch/HotReloadClient/Web/StaticWebAssetsManifest.cs	Uses structured log event for missing manifest file.
src/Dotnet.Watch/HotReloadClient/Logging/LogEvents.cs	Adds new ManifestFileNotFound log event.

[jonathanpeppers]

Looks good, but I wonder about the project references, where $(TargetFramework) wouldn't match exactly.

[DustinCampbell]

Is this a Roslyn bug that should be fixed?

[tmat]

Not a bug. Currently it's in the project name set by the project system and we regex match it. For single-TFM project the project system doesn't even pass us the TFM.

It'd be certainly better if the project system always passed us TFM as a separate property and it was a first class property of Roslyn's Project type.

[JoeRobich]

I have wanted that recently too (dotnet/roslyn#82102)

[tmat]

Nice. It's possible you might need to change project system.

[tmat]

Looks good, but I wonder about the project references, where $(TargetFramework) wouldn't match exactly.

See tests in 135c143