Bsb is ReScript's build system. User-facing documentations are here.
This directory hosts its implementation. It reads into bsconfig.json, uses some BS/OCaml/Reason-specific logic, and generates a ninja build file then calls ninja on it. So much of the incremental build and perf work is delegated to Ninja.
There's a templates/ subdirectory. It's the thing shown when you do bsb -themes. To generate a template for the user, it basically picks the chosen template from templates/ and copy pastes it into the destined user directory while substituting some strings in those templates, like ${rescript:proj-version} in the package.jsons.
The content of templates is packed into bsb_templates.ml automatically when running pack.js.
When adding/editing a template the script needs to be rerun to update the relevant parts in bsb_templates.ml.
Do the following setup steps to build the compiler: build ocaml compiler and build everything in dev mode.
The built binaries will end up under lib where you can run local bsb:
./bsb -init test-theme -theme new_theme