fallout.canary

Early-warning canary for Fallout. It consumes Fallout's published GitHub Packages -preview feed exactly like a real user would — references the packages, runs real builds — to catch regressions that the framework's own unit tests can't:

• packaging gaps (Pack produces a package that doesn't actually restore/build for a consumer);
• source generators that work against a project reference but not against the packaged analyzer;
• the dotnet fallout global tool failing to install or run;
• the Nuke.* → Fallout.* transition shims failing to compile/run for a mid-migration consumer.

If a scenario's build breaks, the canary opens (or updates) an issue here, labelled canary-failure, and auto-closes it when the scenario goes green again.

This repo contains no product code — only consumer projects that exercise the released artifacts. The design rationale lives in docs/DESIGN.md.

How it works

release on Fallout (-preview → GitHub Packages)
        │  repository_dispatch: fallout-preview-published
        ▼
   canary CI  ──┬── scenario: minimal           ─┐
   (also runs   ├── scenario: transition-shims    ├─ each = a real consumer build
    nightly +   └── …                             ─┘   floated to the latest -preview
    on demand)
        │
        ├─ all green → close any open canary-failure issues
        └─ a scenario fails → open/update its canary-failure issue

• Triggers: repository_dispatch from Fallout's release on every -preview publish (fast feedback) + a nightly schedule (safety net) + manual workflow_dispatch.
• Floating: scenarios reference 2026.1.*-*, so every run pulls the newest -preview. The resolved version is printed in each run's log.
• Isolation: one CI job per scenario (fail-fast: false) — one broken scenario doesn't mask the others.

Scenario tiers

Tier	Scenario	Asserts
0 — smoke	minimal	Fallout.Common restores from the feed; a build with Restore/Compile targets compiles (source generator ran) and drives the dotnet tool wrapper.
2 — compat	transition-shims	A build authored against the legacy Nuke.* namespaces (class Build : NukeBuild) compiles and runs against the Nuke.Common shim package.

Tiers 1 (tool wrappers, global tool) and 3 (large target graph, multi-solution, IDE tooling) are sketched in the design doc and land incrementally.

Add a scenario

1. Create scenarios/<name>/ with a Fallout consumer build at scenarios/<name>/build/_build.csproj and a Build.cs whose default target is what you want exercised.
2. Reference the released package(s) with a floated version: Version="2026.1.*-*".
3. Add <name> to the scenario matrix in .github/workflows/canary.yml.

A scenario "passes" when its build exits 0. For stronger guarantees, add assertions on the build output inside the build's targets (fail the target if an expected artifact/member is missing).

Running locally

# A PAT with read:packages on the Fallout-build org:
export FALLOUT_PACKAGES_TOKEN=ghp_xxx
dotnet run --project scenarios/minimal/build/_build.csproj