Generators and mix tasks

Caravela ships one mix task per generator, plus an all-in-one task for the backend trio. All tasks accept --dry-run (print, don't write), --force (overwrite without prompting), and --output DIR (write under DIR instead of File.cwd!()).

All file paths use standard Phoenix conventions:

lib/my_app/library/book.ex            # schema
lib/my_app/library.ex                 # context
lib/my_app_web/controllers/book_controller.ex
lib/my_app_web/schema/library_types.ex     (GraphQL)
lib/my_app_web/live/library/book_live/index.ex
assets/svelte/library/BookIndex.svelte     (LiveSvelte)
assets/svelte/types/library.ts             (TypeScript)
priv/repo/migrations/<ts>_create_library_tables.exs

Versioned domains nest a v<n>/ segment in module names and file paths; see versioning.

Flags specific to mix caravela.gen.live

• --with-domain — in addition to the three per-entity LiveViews (index, show, form), also emit a Caravela.Live.Domain companion module (e.g. MyAppWeb.Library.BookLive.FormDomain) and generate form.ex from the Template-backed variant. Index and show stay plain. Useful as an onramp to the Live runtime.

mix caravela.gen.live --with-domain MyApp.Domains.Library
# → lib/my_app_web/live/library/book_live/form.ex
#   lib/my_app_web/live/library/book_live/form_domain.ex

Optional dependencies

Caravela's own deps are minimal (ecto_sql, jason). These are only required if you use the corresponding generator:

# GraphQL (mix caravela.gen.graphql)
{:absinthe, "~> 1.7"},
{:absinthe_plug, "~> 1.5"},
{:dataloader, "~> 2.0"},

# LiveSvelte (mix caravela.gen.live)
{:live_svelte, "~> 0.19"},

# Phoenix (any generator targeting web code)
{:phoenix, "~> 1.7"},
{:phoenix_live_view, "~> 1.0"},
{:postgrex, "~> 0.18"}

The mix tasks check at runtime and print a useful error if a dep is missing.

Router snippets

Caravela does not edit router.ex automatically. Instead, each web generator prints a scope block you paste in:

# from mix caravela.gen.api
scope "/api", MyAppWeb do
  pipe_through :api
  resources "/books", BookController, except: [:new, :edit]
end

# from mix caravela.gen.live
scope "/library", MyAppWeb do
  pipe_through :browser
  live "/books", BookLive.Index, :index
  live "/books/new", BookLive.Form, :new
  live "/books/:id", BookLive.Show, :show
  live "/books/:id/edit", BookLive.Form, :edit
end

See the regeneration page for the sha256 header, per-function CUSTOM blocks, and tail-marker semantics that make re-runs safe.

Render functions are pure

Every Caravela.Gen.*.render/1,2 function is a pure function of the compiled domain module — it builds a {path, source} tuple (or a list of them) in memory and never touches the filesystem or starts Mix. The mix tasks are thin CLI wrappers around these calls.

That means you can invoke a generator anywhere you have the domain module loaded: from a test, from a Phoenix controller that previews generator output, from an IEx session. Nothing special about the mix entry point.

domain = MyApp.Domains.Library.__caravela_domain__()
{path, src} = Caravela.Gen.Context.render(domain)
# `src` is the file contents; `path` is where the mix task *would*
# write it. Up to you whether to write, diff, or render inline.

Deterministic migration output

Caravela.Gen.Migration.render/2 stamps the current UTC time into the migration filename prefix by default, so two back-to-back runs produce different paths. For snapshot tests or demo pages that show generator output side-by-side with a committed baseline, pin the prefix:

Caravela.Gen.Migration.render(domain, timestamp: "00000000000000")
# → {"priv/repo/migrations/00000000000000_create_library_tables.exs", ...}

All other generators are already deterministic.