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add-dotnet-aot-command

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Include a dotnet CLI command or feature in the Native AOT CLI (src/Cli/dotnet-aot) and prove it works. USE FOR: enabling a command/option in dotnet-aot, adding source files to AotSourceFiles.props, gating AOT-incompatible code with #if CLI_AOT, building and NativeAOT-publishing dotnet-aot, writing/updating the AOT parser + integration tests, running the local dn harness in AOT mode and comparing it to the managed CLI. DO NOT USE FOR: resolving IL trim/AOT analyzer warnings (use dotnet-aot-compat), running dotnet.Tests incrementally (use incremental-test), or pure managed CLI work.

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add-dotnet-aot-command

How to include a dotnet command or feature in the Native AOT CLI (src/Cli/dotnet-aot), keep the AOT surface small, validate it, and run it through the local dn harness.

Paths use $(SdkTargetFramework) = net11.0 and win-x64; adjust for other TFMs/RIDs.

When to use

  • Make dotnet <x> work in dotnet-aot, or enable an option/section in the AOT path.
  • Add source files to AotSourceFiles.props.
  • Run dn in AOT mode, or compare AOT vs managed output.
  • Diagnose why dotnet test fails for dotnet-aot.Tests.

Not for: IL trim/AOT warnings (use dotnet-aot-compat); managed dotnet.Tests runs (use incremental-test); managed-only changes with no AOT impact.

How the AOT CLI is assembled

dotnet-aot does not reference dotnet.csproj. It is a shared native library (NativeLib=Shared, PublishAot=true, IsAotCompatible=true) that cherry-picks source files from src/Cli/dotnet/ via src/Cli/dotnet-aot/AotSourceFiles.props. That .props is imported by both dotnet-aot.csproj and test/dotnet-aot.Tests/dotnet-aot.Tests.csproj, so the tests compile the exact same command surface as the shipping binary.

Compile constants (both projects): CLI_AOT gates AOT-only vs managed-only code in shared files (#if CLI_AOT / #if !CLI_AOT); DotnetCsproj is also defined and can pull in extra closure (see Gotchas).

Dispatch: dotnet-aot/NativeEntryPoint.cs (dotnet_execute) is P/Invoked by the dn host (src/Cli/dn):

  • DOTNET_CLI_ENABLEAOT=true: parse in-process, run FirstRunExperience.Setup, and if parseResult.CanBeInvoked() run the command in-process. A command still needing the managed CLI throws CommandNotAvailableInAotException to fall through.
  • Otherwise / on fall-through: host {sdkDir}/dotnet.dll via hostfxr (same source, JIT-compiled).

Types already available (do not re-add their sources): Microsoft.DotNet.Cli.Utils, Microsoft.DotNet.Configurer, Microsoft.DotNet.Cli.Definitions, Microsoft.DotNet.ProjectTools, Microsoft.DotNet.NativeWrapper, Microsoft.NET.Sdk.WorkloadManifestReader. Cli.Utils grants InternalsVisibleTo to dotnet-aot and dotnet-aot.Tests, so its internal types (including the CsWin32 Windows.Win32.* COM types and helpers ComScope, BSTR, HRESULT, CLSID) are usable without re-wiring CsWin32.

Resolving the versioned SDK root (do NOT use BCL path APIs)

The muxer loads dotnet-aot.dll directly from the versioned SDK directory (e.g. .../sdk/11.0.100/), but inside that process the BCL "where am I" APIs do not point there:

  • AppContext.BaseDirectory, Environment.ProcessPath, Process.GetCurrentProcess().MainModule -> the muxer / install root.
  • Assembly.Location -> the empty string (ILC hard-errors with IL3000).

So deriving an SDK-relative path (MSBuild.dll, Sdks/, DotnetTools/, targets) from AppContext.BaseDirectory or a dll path is wrong in the AOT bubble. Instead:

  • In-repo: read SdkPaths.SdkDirectory (in Microsoft.DotNet.Cli.Utils), which resolves the Microsoft.DotNet.Sdk.Root AppContext value -> SDK assembly directory -> AppContext.BaseDirectory (once, cached).

  • NativeEntryPoint.ExecuteCore resolves the SDK directory once (host sdk_dir, else self-locating the dotnet-aot module via SdkRootLocator) and publishes it as the Microsoft.DotNet.Sdk.Root AppContext value for the compiled-in assemblies.

  • Out-of-repo code (MSBuild tasks, NuGet, runtime - no Cli.Utils reference) replicates the contract inline: read the Microsoft.DotNet.Sdk.Root AppContext value first, else the existing BCL logic.

    string sdkDirectory =
    AppContext.GetData("Microsoft.DotNet.Sdk.Root") is string sdkRoot && sdkRoot.Length > 0
        ? sdkRoot
        : /* existing logic, e.g. AppContext.BaseDirectory */;

When bringing a command into AOT, switch any AppContext.BaseDirectory / Assembly.Location used as "the SDK directory" to the above. Not-yet-routed sites: FormatForwardingApp, FsiForwardingApp, VSTestForwardingApp, ProjectFactory / ProjectToolsCommandResolver, VBCSCompilerServer, CSharpCompilerCommand, MSBuildForwardingAppWithoutLogging, DotnetFiles.SdkRootFolder. Details: src/Cli/dotnet-aot/SdkRootResolution.md.

Procedure

  1. Find the call site in shared source (a command parser, Parser.cs, ParserOptionActions.cs) and remove/narrow its #if !CLI_AOT guard.
  2. Add the source closure to AotSourceFiles.props in a labeled per-command <ItemGroup> (follow the file's header rules; reuse the "Common AOT scaffolding" group). Only add files under src/Cli/dotnet/ that aren't already in a referenced assembly or the .props. Windows/COM files go in a Condition="'$(TargetOS)' == 'windows'" group.
  3. Add package references the command needs (in AotSourceFiles.props if both binary and tests need them; confirm the runtime asset flows - see the Microsoft.Build gotcha).
  4. Build managed dotnet-aot first - fast, and surfaces CS0246/CS0103 closure gaps without ILC. Let the compiler drive the closure: .\.dotnet\dotnet build src\Cli\dotnet-aot\dotnet-aot.csproj -c Debug
  5. Publish as NativeAOT to surface IL warnings (resolve per dotnet-aot-compat): .\.dotnet\dotnet publish src\Cli\dotnet-aot\dotnet-aot.csproj -r win-x64 -c Debug. ILC only analyzes the reachable closure - don't preemptively suppress warnings that never appear.
  6. Keep the AOT surface small. Gate heavy subsystems (workload installer, NuGet engine, MSI/COM IPC) under #if CLI_AOT and build only the read-only path you need (mirror WorkloadInstallDetector, which builds the record repository directly with no installer). Gate installer-coupled interfaces under #if !CLI_AOT, with an AOT-only construction path under #if CLI_AOT.
  7. Confirm the managed CLI still builds (the #else branches must stay intact): .\.dotnet\dotnet build src\Cli\dotnet\dotnet.csproj -c Debug

Gotchas

  • MSBuild XML comments can't contain -- (MSB4024). Reword; never end a comment with -.
  • The Microsoft.Build runtime asset doesn't flow transitively - Cli.Utils references it ExcludeAssets="runtime" PrivateAssets="all", so dotnet-aot has no Microsoft.Build.dll at ILC time. If you reach a Microsoft.Build.* API, add <PackageReference Include="Microsoft.Build" /> to the AOT closure.
  • DotnetCsproj is defined for dotnet-aot, so adding a shared file can pull in extra #if DotnetCsproj closure. Inline the small helper you need under #if CLI_AOT instead.
  • Don't pass -noRestore with -getItem - the response file already appends it (MSB1001).
  • dotnet test does NOT work for dotnet-aot.Tests (Microsoft.Testing.Platform, not VSTest). Run the built .exe directly (see below).
  • Existing tests may assert AOT exclusions - enabling a feature can mean inverting a DoesNotContain assertion. Search the test project first.
  • PowerShell git/gh quoting: single-quote messages/titles containing backticks or $(...).

Validate & test

Tests live in test/dotnet-aot.Tests: AotParserTests (in-process parser/command behavior) and AotIntegrationTests (end-to-end against the real dn; skips if dn isn't in the layout).

Run the suite as a native AOT binary (the real ILC / COM / P-Invoke check) with test/dotnet-aot.Tests/run-aot-tests.ps1. To iterate on one test, build the test project and run dotnet-aot.Tests.exe --filter "FullyQualifiedName~<name>" (MTP runs as an executable; dotnet test doesn't work). IL3053 rollups for test-only assemblies (FluentAssertions, TestPlatform.ObjectModel, DataContractSerialization) are not product warnings.

Assert real values, not just headers, so a trim regression that blanks a line is caught - e.g. stdout.Should().MatchRegex(@"MSBuild version:\s+\S");.

Run the local dn harness in AOT mode

Use src/Cli/dn/run-dn.ps1 (don't inline the steps). It publishes dotnet-aot (NativeAOT) and dn, builds the managed dotnet CLI, assembles them into the dn publish dir, points DOTNET_ROOT at the repo's .dotnet, and runs dn <command> with DOTNET_CLI_ENABLEAOT toggled. Tell the user these steps so they can reproduce it.

src\Cli\dn\run-dn.ps1 -Command "--info"                    # through the AOT binary
src\Cli\dn\run-dn.ps1 -Command "--info" -Mode Compare      # AOT vs managed diff (parity)
src\Cli\dn\run-dn.ps1 -Command "workload --info" -NoBuild  # reuse the assembled layout
  • DOTNET_CLI_ENABLEAOT=true runs in-process in dotnet-aot.dll; unset, dn hosts the copied dotnet.dll. -Mode Compare diffs the captured output (artifacts/log/dn-aot.txt, dn-managed.txt).
  • dn finds the .NET root from DOTNET_ROOT (set to .dotnet); the publish dir isn't a full SDK.
  • The AOT path runs FirstRunExperience.Setup first; if it can't complete, it defers to the managed CLI.
  • Commit and workloads reflect the DOTNET_ROOT layout - both paths read the same root, so they agree.

The VS Code tasks publish-and-copy-dn-aot + copy-all-deps do the same build/assemble.

Related skills

  • dotnet-aot-compat - resolve the IL trim/AOT warnings this surfaces.
  • incremental-test - run the managed dotnet.Tests against the redist SDK layout.