Description

Paket.Restore.targets' Step 2a invalidates the per-project restore skip only when the content hash of paket.references changes. When paket.lock is updated by a transitive change — e.g. a merge that bumps a transitive package version — paket.references content is unchanged, Step 2a's skip kicks in, and the per-project obj/<rid>/<proj>.fsproj.paket.props stays at the pre-merge content. Subsequent dotnet restore reads it via $(BaseIntermediateOutputPath) and project.assets.json continues resolving the package to the previous version indefinitely. Neither dotnet paket restore, dotnet paket restore --force, nor dotnet restore --force-evaluate fixes the project's resolved view.

The bug shows up most visibly when BaseIntermediateOutputPath is redirected (e.g. obj/$(_BuildPlatform)/) because the platform-agnostic obj/<proj>.fsproj.paket.props does get rewritten by the CLI's full restore but the platform-specific copy at obj/<rid>/<proj>.fsproj.paket.props (which is what MSBuild actually reads) does not.

Repro steps

1. Small SDK-style F# project that pulls in a single package transitively. Directory.Build.props redirects BaseIntermediateOutputPath to obj/custom/ (mirrors the existing i003527 scenario layout).
2. dotnet restore project.fsproj — establishes steady state. Per-project files in obj/custom/ reflect the lock.
3. Mutate paket.lock content (e.g. append a comment line to simulate a transitive bump). Do not touch paket.references.
4. dotnet restore project.fsproj again, with PAKET_ERROR_ON_MSBUILD_EXEC=true to assert whether a per-project paket restore fires.

Expected behavior

The per-project skip should treat a paket.lock content change as an invalidation event and re-run the per-project restore, just as it does on a paket.references content change.

Actual behavior

PAKET_ERROR_ON_MSBUILD_EXEC=true does not fire — Step 2a sets PaketRestoreRequired=false because paket.references hash matches the cached hash, and Step 2b sees the resolved files exist. obj/<rid>/<proj>.fsproj.paket.props stays at the pre-mutation content; project.assets.json continues resolving the affected package to the old version.

Known workarounds

• Delete obj/<rid>/ for the affected projects to force DoAllResolvedFilesExist=false (Step 2b then fires). Heavy hammer; loses build outputs.
• dotnet paket install --force (re-resolves and rewrites all per-project state). Heavy hammer; touches the lock.
• Set PAKET_SKIP_RESTORE_TARGETS=true and patch Paket.Restore.targets locally to add the missing check. Workable but requires every developer / CI / IDE to set the env var.

I have a candidate fix and an integration test (red/green) that follows the same shape as i002684-fast-restore and i003527; PR to follow this issue.