install-deps: isolate failures so one bad dep never blocks the rest

[JPDuchesne]

One integration failing aborted the whole install-deps run — during d3mlabs/plans#36 leg-2 validation, the brew wwise-cli failure (Homebrew unwritable by ai-agent) aborted the Installer's bare-each dispatch, so the unrelated cmake integration never ran and googletest was never fetched. The same bare-each pattern lived inside brew/gh/cmake install_all.

The manifest declares no cross-integration edges, so the failure policy for the (degenerate) dependency DAG is attempt-all:

• Integration#collect_failures isolates per-dep failures; brew, gh, cmake raise Integration::PartialInstallError after attempting every dep.
• Preamble failures (brew tap registration) still fail the integration as one entry — every dep is predetermined to fail for the same root cause.
• cmake only rewrites deps.cmake/deps.targets.cmake when every dep succeeded (stale-but-consistent, same philosophy as the install stamp).
• Installer#dispatch rescues per integration and aggregates into InstallFailedError, entries ordered by wave (root causes before derivative failures). Raising preserves stamp semantics — no stamp on any failure — and the non-zero exit.

Test-first: the six new tests were written and confirmed failing before the fix (the installer test failed with exactly the incident shape: googletest never dispatched). Full suite green except the 4 pre-existing BuildContainerTest failures that also fail on clean main on this machine.

When real cross-integration edges appear, the build-wave partition generalizes to a topological sort and failure propagation follows the DAG — this design degrades into that without changing shape.

Made with Cursor

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!