doc: add dlang language section

doc/languages-frameworks/dlang.section.md

@@ -0,0 +1,69 @@
+# D (Dlang) {#dlang}
+
+Nixpkgs provides multiple D compilers such as `ldc`, `dmd` and `gdc`.
+These can be used like any other package during build time.
+
+However, Nixpkgs provides a build helper for compiling packages using the `dub` package manager.
+
+Here's an example:
+```nix
+{
+  lib,
+  buildDubPackage,
+  fetchFromGitHub,
+  ncurses,
+  zlib,
+}:
+
+buildDubPackage rec {
+  pname = "btdu";
+  version = "0.5.1";
+
+  src = fetchFromGitHub {
+    owner = "CyberShadow";
+    repo = "btdu";
+    rev = "v${version}";
+    hash = "sha256-3sSZq+5UJH02IO0Y1yL3BLHDb4lk8k6awb5ZysBQciE=";
+  };
+
+  # generated by dub-to-nix, see below
+  dubLock = ./dub-lock.json;
+
+  buildInputs = [
+    ncurses
+    zlib
+  ];
+
+  installPhase = ''
+    runHook preInstall
+    install -Dm755 btdu -t $out/bin
+    runHook postInstall
+  '';
+}
+```
+
+Note that you need to define `installPhase` because `dub` doesn't know where files should go in `$out`.
+
+Also note that running `dub test` is disabled by default. You can enable it by setting `doCheck = true`.
+
+## Lockfiles {#dub-lockfiles}
+Nixpkgs has its own lockfile format for `dub` dependencies, because `dub`'s official "lockfile" format (`dub.selections.json`) is not hash based.
+
+A lockfile can be generated using the `dub-to-nix` helper package.
+* Firstly, install `dub-to-nix` into your shell session by running `nix-shell -p dub-to-nix`
+* Then navigate to the root of the source of the program you want to package
+* Finally, run `dub-to-nix` and it will print the lockfile to stdout. You could pipe stdout into a text file or just copy the output manually into a file.
+
+## `buildDubPackage` parameters {#builddubpackage-parameters}
+
+The `buildDubPackage` function takes an attrset of parameters that are passed on to `stdenv.mkDerivation`.
+
+The following parameters are specific to `buildDubPackage`:
+
+* `dubLock`: A lockfile generated by `dub-to-nix` from the source of the package. Can be either a path to the file, or an attrset already parsed with `lib.importJSON`.
+  The latter useful if the package uses `dub` dependencies not already in the lockfile. (e.g. if the package calls `dub run some-dub-package` manually)
+* `dubBuildType ? "release"`: The build type to pass to `dub build` as a value for the `--build=` flag.
+* `dubFlags ? []`: The flags to pass to `dub build` and `dub test`.
+* `dubBuildFlags ? []`: The flags to pass to `dub build`.
+* `dubTestFlags ? []`: The flags to pass to `dub test`.
+* `compiler ? ldc`: The D compiler to be used by `dub`.

doc/languages-frameworks/index.md

@@ -14,6 +14,7 @@ cuda.section.md
 cuelang.section.md
 dart.section.md
 dhall.section.md
+dlang.section.md
 dotnet.section.md
 emscripten.section.md
 gnome.section.md