Ship assembly-differ as a native-AOT dotnet tool

[Mpdreamz]

assembly-differ ships as a self-contained native-AOT executable on five platforms, with its CLI now parsed by Nullean.Argh instead of Mono.Options.

Prompt summary: Modernize this repo's build tooling the way curb and mermaider already do — package the tool as native-AOT dotnet tools per-RID with a framework-dependent fallback, and move CLI parsing onto Nullean.Argh everywhere instead of the mix of parsers the sibling tool repos had accumulated.

Why

assembly-differ only shipped as a framework-dependent tool: every invocation paid a JIT warmup cost, and installing it required the matching .NET runtime already present. dotnet pack also had a latent bug where the unsigned obj/ build of this project's own assembly, not the correctly signed bin/ one, ended up inside the portable any package — nupkg-validator's signature check silently checked the wrong bytes. CLI parsing used Mono.Options, a hand-rolled reflection-free parser with no source generation and an unused Argu reference left over from an earlier attempt.

What

Native-AOT packaging

assembly-differ.csproj gains linux-x64, linux-arm64, win-x64, win-arm64, and osx-arm64 as RuntimeIdentifiers, with PublishAot, PublishSelfContained, and StripSymbols scoped to builds that target a specific RID so the managed any fallback keeps its signed assembly. NuGet.Protocol and Newtonsoft.Json are rooted for the trimmer — the nuget/previous-nuget providers go through NuGet.Protocol's repository-signature check, which needs Newtonsoft.Json's reflection-based constructor resolution that trimming would otherwise strip.

CLI parsing

DiffCommand.cs replaces Program.cs's Mono.Options.OptionSet wiring with a Nullean.Argh command registered via MapAndRootAlias, so diff can still be omitted when a flag precedes the two provider arguments. --prevent-change stays string-typed and is parsed by hand with Enum.Parse — Argh 0.18.0 fails to compile an enum parameter whose default member has a non-zero underlying value (SuggestedVersionChange.None = 1), filed as nullean/argh#75. The net8.0 leg also needed <LangVersion>latest</LangVersion>: the generated parser uses a C# 13 feature (ref/unsafe in async iterators) that net8.0's default language version doesn't support.

Package staging and signing

generatePackages now runs a full dotnet pack into a staging directory and keeps only the root and any packages — the real per-RID packages come from CI, each compiled on a matching runner, since AOT can't cross-compile. A new fixAnyPackageSigning helper re-signs the any package's assembly, replacing the unsigned obj/ copy dotnet pack picks up with the signed one from bin/. validatePackages now points at the any package specifically and checks against currentVersionInformational, which includes the git SHA suffix modern SDKs append.

CI

.github/workflows/ci.yml adds an aot-pack matrix job that builds each RID package on a matching runner, ahead of the build job, which downloads and merges the per-RID artifacts before packages get published. actions/checkout and actions/setup-dotnet move to v5.

Dependencies

NuGet.Frameworks/Versioning/Protocol/Packaging/Resolver/Common move from 6.13.1 to 7.9.0 — 7.9.0's NuGet.Protocol drops its direct Newtonsoft.Json dependency for net8.0+ in favor of System.Text.Json, though the trimmer-root workaround above is still needed since Newtonsoft.Json still arrives transitively through NuGet.Packaging. The unused Argu package reference is removed — this project's CLI was never actually parsed with Argu.

Breaking

Mono.Options had no subcommand concept, so assembly-differ was invoked as a bare <old> <new> [options]. Argh needs a diff subcommand unless an option precedes the two provider arguments — a provider spec as the very first argument (assembly-differ "nuget|..." "nuget|...") now fails and needs assembly-differ diff "nuget|..." "nuget|...". --target also moves from a single comma/pipe-separated value (--target a,b) to a repeatable flag (--target a --target b).

Out of scope

nupkg-validator, release-notes, and assembly-rewriter each pin an older, pre-Argh assembly-differ release in their dotnet-tools.json and call it positional-first. Bumping those pins and adding diff to their invocations happens in a follow-up once this ships, so their CI doesn't break against a tool version they don't yet depend on.

Verify

./build.sh build generatepackages validatepackages generateapichanges -s true
dotnet tool install --add-source build/output assembly-differ
assembly-differ diff "directory|src/assembly-differ/bin/Release/net10.0" "directory|src/assembly-differ/bin/Release/net10.0" --target assembly-differ