Jean-Pierre

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transform merge attributes never run on JP's config path ​

  • Status: Todo
  • Kind: Chore
  • Authors: jp
  • Date: 2026-08-24
  • Label: package=jp_config
  • Label: package=schematic
  • Label: type=bug

A #[setting(transform = ...)] declaration has no effect in JP.

Transforms are applied by PartialConfig::finalize, which is called from exactly one place — ConfigLoader::load (crates/contrib/schematic/src/config/loader.rs:127). JP never calls it: jp_config::util::load_partial_at_path uses loader.load_partial(&()), and resolution goes through AppConfig::from_partial_with_defaults. So a declared transform is silently dead.

finalize is not usable as-is either. It applies defaults, then the partial, then env vars in one shot, but JP already applies env separately (load_envs) and defaults separately, and the defaults step deliberately fills rather than merges (that is what FillDefaults exists for). Calling finalize would double-apply env and route defaults through the merge strategies, so an appending default would append to itself.

Current state ​

#887 removed both existing uses rather than leaving them dead:

  • AppConfig::config_load_paths and AnthropicConfig::beta_headers both declared transform = util::vec_dedup on top of merge = append_vec. Both now use internal::merge::append_vec_dedup, which does the append and the dedup in one step, and util::vec_dedup is deleted.

So there are no transform declarations left in jp_config. The hazard is that the next one added will silently do nothing.

Options ​

  1. Remove transform support from schematic_macros. Turns a silent no-op into a compile error. Cheapest, and matches the "fail loudly" direction #887 took with invalid #[setting] keys.
  2. Apply transforms on JP's path. Generate a transform_values() on the partial that runs only the transforms, and call it from jp_config::util::build. Keeps the feature, needs macro work and a decision about where in the pipeline it runs.

Option 1 is the smaller change and nothing currently needs the feature.

Context ​

Found in #887 while writing a merge test for config_load_paths — the first draft asserted the resolved config was deduplicated and failed. Disclosed in review comment 3659114885.