pub type DirectoryMergeFn = fn(&AssemblerConfig, &[FileInfo], &[usize]) -> Vec<(Option<Package>, Vec<TopLevelDependency>, Vec<usize>)>;Expand description
A bespoke per-directory merge for a layout the generic sibling / per-identity / one-per engines cannot express.
Runs in place of the generic per-directory engine for the directories a
config claims; the config’s AssemblyMode still governs the later
nested-merge pass, so a config keeps SiblingMerge even when it supplies a
merger. Returning an empty result is an explicit “skip per-directory
assembly” (used by Swift, which is assembled by a post-assembly pass).