Configuration

moltn works without configuration. An optional moltn.toml file declares another folder layout or tunes moltn dev. A project created by moltn new contains one, fully commented out.

Keys

All of them are optional; these are the defaults:

[front]
dir = "web"                             # frontend folder, relative to moltn.toml

[pages]
dir = "src/pages"                       # relative to front.dir
typescript = "src/generated/moltn.ts"   # relative to front.dir

[dev]
port = 3000
vite_port = 5173
cargo = ["run"]                         # cargo arguments that run the application
watch = ["src", "Cargo.toml", "build.rs"]   # changes that restart it

• pages.typescript: without this key, the file follows the pages folder (generated/moltn.ts next to it).
• dev.cargo: in a workspace with several binaries, ["run", "-p", "my-app"]. moltn gen uses the same command.
• dev.watch: files and folders, relative to moltn.toml. A folder stands for all its files: add your migrations, your templates, a neighbouring crate.
• A command-line option (--port, --vite-port, --web) wins over the file.
• An unknown key is an error that names it: a typo is never silently ignored.

moltn doctor prints the effective configuration.

Where to put the file

Next to the application's Cargo.toml, or in a parent folder. The moltn commands look for it from the current folder upwards and move into its folder, so they can be run from any subfolder.

On the Rust side, build.rs reads it with scan_project():

fn main() {
    if let Err(e) = moltn_pages::build::scan_project() {
        panic!("{e}");
    }
}

Example: server and frontend side by side

my-app/
├── Cargo.toml        # [workspace] members = ["server"]
├── moltn.toml
├── server/           # Rust crate: Cargo.toml, build.rs, src/, migrations/
└── web/              # frontend

# moltn.toml
[dev]
watch = ["server/src", "server/migrations", "server/Cargo.toml", "server/build.rs"]

The frontend is already in web/ (the default). In server/src/main.rs, paths read at compile time are relative to the crate:

#[derive(rust_embed::RustEmbed)]
#[folder = "../web/dist/client/"]
struct Assets;

let ssr = EmbeddedSsr::builder(moltn_ssr::embedded_bundle!("../web/dist/ssr/ssr.js")).build()?;

What is not configured here

• Page naming conventions ([id], [[tab]], [...slug], (group), _ignored).
• Server-side rendering settings (number of engines, timeout, memory): they stay in the code, see Server-side rendering.
• The frontend entry and the asset prefix: still written in vite.config.ts (options of moltn()) and in main.rs.