Module registry 

The settings a CLI has, as a generated table.

#[derive(usage::Config)] reads the settings struct and emits a static of these, so at runtime a registry is a slice — no parsing, no map to build, and a PropId that indexes it directly. A merge over a hundred settings therefore never hashes a key, which is what makes resolving the whole struct at once cheap enough to do eagerly.

Keys are the dotted paths the spec declares. Nesting is a file’s concern, reconstructed by whatever reads the file; here a key is one string.

Structs

Lookup

What looking a key up found.

PropId

A setting’s index in its registry.

PropMeta

What one setting is.

Registry

Every setting a CLI has.

Enums

Merge

How the values for one setting combine when several layers supply them.

Scope

Where a setting will accept a value from.