writ deploy panics on a distribution pkg/platform does not know: the detection error is swallowed and ParseIdentifier calls a method on the nil platform #968

On a Linux host whose os-release ID is outside pkg/platform's ten (pkg/platform/defaults.go:31-42), writ's deploy panics while merging packages manifests. Pop!_OS is an example: ID=pop, ID_LIKE="ubuntu debian".

• platform.Detect refuses the ID (pkg/platform/detect_linux.go:47-50).
• op.NewRuntimeEnvironment discards that error, leaving Platform nil (pkg/op/runtime_environment.go:223-227).
• mergeManifests passes the nil platform to platform.ParseIdentifier for every non-registry entry (cmd/writ/writ/deploy/manifest.go:95, :163).
• ParseIdentifier has no nil guard, and calls plat.DefaultPurlType() on the nil interface (pkg/platform/identifier.go:58), or plat.ResolvePurlType for a pkg: form (:44). Calling a method on a nil interface panics.

This is read from the code at 9cd1e95d on 2026-09-28 and confirmed line by line, but not run on such a host. lore's pkg provider guards the same case ("no platform available", pkg/op/provider/pkg/provider.go:418-425); writ's merge does not.

Resolution

A nil platform with native claims to merge is an error naming the host's ID, not a panic. The underlying refusal of derivatives is #944's: detection falls back along ID_LIKE.

Plan and design documents

Epic: #447 · Feature: #463