depot/doc/languages-frameworks/idris2.section.md

Idris2

In addition to exposing the Idris2 compiler itself, Nixpkgs exposes an idris2Packages.buildIdris helper to make it a bit more ergonomic to build Idris2 executables or libraries.

The buildIdris function takes an attribute set that defines at a minimum the src and ipkgName of the package to be built and any idrisLibraries required to build it. The src is the same source you're familiar with and the ipkgName must be the name of the ipkg file for the project (omitting the .ipkg extension). The idrisLibraries is a list of other library derivations created with buildIdris. You can optionally specify other derivation properties as needed but sensible defaults for configurePhase, buildPhase, and installPhase are provided.

Importantly, buildIdris does not create a single derivation but rather an attribute set with two properties: executable and library. The executable property is a derivation and the library property is a function that will return a derivation for the library with or without source code included. Source code need not be included unless you are aiming to use IDE or LSP features that are able to jump to definitions within an editor.

A simple example of a fully packaged library would be the LSP-lib found in the idris-community GitHub organization.

{ fetchFromGitHub, idris2Packages }:
let lspLibPkg = idris2Packages.buildIdris {
  ipkgName = "lsp-lib";
  src = fetchFromGitHub {
   owner = "idris-community";
   repo = "LSP-lib";
   rev = "main";
   hash = "sha256-EvSyMCVyiy9jDZMkXQmtwwMoLaem1GsKVFqSGNNHHmY=";
  };
  idrisLibraries = [ ];
};
in lspLibPkg.library { withSource = true; }

The above results in a derivation with the installed library results (with sourcecode).

A slightly more involved example of a fully packaged executable would be the idris2-lsp which is an Idris2 language server that uses the LSP-lib found above.

{ callPackage, fetchFromGitHub, idris2Packages }:

# Assuming the previous example lives in `lsp-lib.nix`:
let lspLib = callPackage ./lsp-lib.nix { };
    inherit (idris2Packages) idris2Api;
    lspPkg = idris2Packages.buildIdris {
      ipkgName = "idris2-lsp";
      src = fetchFromGitHub {
         owner = "idris-community";
         repo = "idris2-lsp";
         rev = "main";
         hash = "sha256-vQTzEltkx7uelDtXOHc6QRWZ4cSlhhm5ziOqWA+aujk=";
      };
      idrisLibraries = [idris2Api lspLib];
    };
in lspPkg.executable

The above uses the default value of withSource = false for the idris2Api but could be modified to include that library's source by passing (idris2Api { withSource = true; }) to idrisLibraries instead. idris2Api in the above derivation comes built in with idris2Packages. This library exposes many of the otherwise internal APIs of the Idris2 compiler.