desi.mod

The project manifest. desic init writes one, and desic build, desic run and desic test read it to decide what to compile and how.

A single .desi file does not need a manifest — desic run hello.desi works on its own. You want one as soon as a project has more than one file, because the manifest is what tells the compiler where your modules live.

What desic init generates

[package]
name    = "myapp"
version = "0.1.0"
edition = "2025"
entry   = "src/main.desi"
roots   = ["src"]

[build]
mode    = "debug"
out_dir = "build"

[target]
triple  = "native"

[diagnostics]
error_format = "human"
color        = "auto"
max_errors   = "100"

[ffi]
libs   = []
search = []

alongside this layout:

myapp/
├── desi.mod
├── src/
│   └── main.desi
├── tests/
│   └── main_test.desi
└── .gitignore

[package]

Key	Meaning
name	Project name. Also the default executable name.
version	Your project's version. Not the compiler's.
edition	Language edition the code targets.
entry	The file whose main runs. Changing it changes what desic run builds.
roots	The one that matters most. Directories searched to resolve import.

roots is why a project needs a manifest at all. With roots = ["src"], a file at src/util/math.desi is reachable as import util.math from anywhere in the project. Add a directory here and its contents become importable; leave one out and its modules cannot be found, whatever the path on disk.

[build]

Key	Values	Meaning
mode	debug, release	release turns on -O2 and link-time optimisation. Debug compiles faster and keeps diagnostics readable.
out_dir	path	Where executables and intermediates land.

desic build --release overrides mode for one invocation, so the manifest sets the default rather than the only option.

[target]

Key	Meaning
triple	native builds for the machine you are on. An explicit LLVM target triple cross-compiles.

[diagnostics]

Key	Values	Meaning
error_format	human, json	json is for editors and CI that parse diagnostics.
color	auto, always, never	auto colours a terminal and stays plain when piped.
max_errors	number	Stops after this many, so one bad line does not print a thousand follow-on errors.

[ffi]

Links C libraries into your program. Empty unless you need it.

Key	Meaning
libs	Libraries to link against, named without the lib prefix or file extension.
search	Extra directories to look for them in, relative to the project root or absolute.

[ffi]
libs   = ["greet", "m"]
search = ["vendor"]

That links greet from vendor/, and the system math library. Declare the functions with @extern and call them:

extern("C", safe=true, c_name="greet_answer")
pub def answer() -> i32

def main() -> int:
    let v = answer()
    print(str(v))
    return 0

The file your library has to be called

A name in libs is resolved by the platform's own convention, because clang is the linker on every target:

• Linux, macOS — greet finds libgreet.a or libgreet.so
• Windows — greet finds greet.lib

A library built with Unix naming will not be found by a Windows build and the error names the file it wanted: could not open 'greet.lib'.

Search paths are emitted before library names, so a search entry applies to every library in libs.

See Safe FFI for the language side — @extern, safe=true, and what the compiler will and will not check for you.

Editing it by hand

The manifest is plain TOML and meant to be edited. The changes worth knowing:

• Adding a source directory — add it to roots, or its modules will not be importable.
• Renaming the entry point — change entry; the file's location is not assumed.
• Shipping a build — set mode = "release", or pass --release.
• Linking a C library — add it to libs, and its directory to search if it is somewhere the linker does not already look.