[fabwa]

Summary

processStructSlice asserted the raw viper value for a struct-slice field directly to []any, and each element directly to map[string]any, both without checking the assertion succeeded. A config field declared as a slice of structs (e.g. Config.GRPC, a shard list) given the wrong shape in YAML - a scalar, or a single mapping instead of a list of mappings - panics with interface conversion: interface {} is ..., not []any instead of being rejected with a clean error.

This is reachable not just at startup (cmd/neofs-node/main.go) but via SIGHUP config reload on an already-running node (cmd/neofs-node/config.go's configWatcher/reloadConfig, neither of which recovers from a panic), turning an operator's config typo into an unplanned process crash instead of a rejected reload.

Fix

processPrimitiveSlice, right below in the same file, already handles the identical situation safely with the comma-ok form: existing, _ := raw.([]any). This PR matches that existing pattern instead of introducing a new error-handling convention: use comma-ok for both assertions, falling back to the already-present zero values (nil list, empty item map) when the stored value isn't shaped as expected.

This doesn't silently swallow the malformed config - viper's value is left untouched, so UnmarshalExact's own mapstructure-based decoding (which already returns a clean, descriptive error for a type mismatch against the destination struct) is reached instead of being pre-empted by a panic.

Test plan

• Added TestEnvUnmarshal_StructSliceAsScalar, confirming Unmarshal returns a clean error instead of panicking when a struct-slice field is given a scalar value.
• Confirmed this test panics against the unpatched code and passes after the fix.
• go vet ./... clean; go test ./internal/configutil/... ./cmd/neofs-node/... passes.
• Patch verified to apply cleanly and pass tests in a separate clean worktree against the current master tip.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 32.71%. Comparing base (34d007f) to head (7136a21).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4282   +/-   ##
=======================================
  Coverage   32.70%   32.71%           
=======================================
  Files         673      673           
  Lines       41698    41701    +3     
=======================================
+ Hits        13638    13643    +5     
+ Misses      28060    28058    -2     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[roman-khimov]

Next one to get in. Please fix conflicts.