e2e: de-globalize BehaviorOnFatal and slog default handler sinks

[bergerx]

Summary

• cmdutil.BehaviorOnFatal was reinstalled by every RootCmd().Execute() call, overwriting a shared closure — concurrent invocations could capture each other's error. Replaced with a checkErr() helper that still uses cmdutil.CheckErr for its message formatting, but scopes the lock (fatalMu) tightly around install-and-consume rather than around the render itself, so it doesn't re-serialize plugin.Run for parallel subtests.
• setupDeprecationFilter rebound the global slog default handler on every render; go-sprout's sprigin reads slog.Default() fresh on every template function call, so concurrent renders would race that rebind. Installed once per process (sync.Once) instead — every record this handler is known to emit carries the deprecated-notice tag it drops, so this is behaviorally identical to before.
• Neither sink can be literally "threaded through the call path" — both are process-global by design in the vendored libraries that own them (kubectl's cmdutil, go-sprout's sprigin), so this scopes/serializes access narrowly instead of eliminating the global.
• Re-audited for other shared cluster-scoped resource names beyond createBadNode and vap-binding.yaml (both already handled) — no other e2e subtest hardcodes a cluster-scoped name another subtest could collide with.

Fixes #701.

Test plan

• go build ./..., go vet ./..., gofmt -l .
• go test ./... (457 tests, non-e2e suite) — includes TestRootCmdWithoutACluster, which exercises the exact checkErr "error: ..." formatting path
• e2e suite against a live minikube cluster (not run in this environment) — routes through the identical checkErr code path, so expected to behave the same

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request addresses concurrency issues related to process-global state. It introduces a mutex (fatalMu) to serialize the installation and consumption of cmdutil's global fatal handler in cmd/main.go, and refactors setupDeprecationFilter in pkg/plugin/render_engine.go to run only once per process using sync.Once. However, the global fatal handler registered in checkErr is never restored to its default state, which can lead to stale closures suppressing errors in subsequent executions. It is recommended to restore the default handler using a deferred call.

Important

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[bergerx]

/gemini review

[gemini-code-assist]

Code Review

This pull request addresses concurrency issues and race conditions by serializing the process-global fatal handler with a mutex in cmd/main.go and using sync.Once to install the global slog deprecation filter in pkg/plugin/render_engine.go. Feedback was provided to defensively return the original error in checkErr if the fatal handler is not triggered, preventing potential silent error swallowing.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.