fix and improve nix build: actually output a proper veloren voxygen package now

2024-08-30 18:12:32 +00:00 · 2020-11-24 04:08:57 +03:00 · 2020-11-24 04:08:57 +03:00 · 62d34422fe
commit 62d34422fe
parent 24e5e714b9
11 changed files with 4528 additions and 2065 deletions
--- a/.gitignore
+++ b/.gitignore
@ -49,4 +49,5 @@ userdata
 .DS_Store

 # Nix
-nix/result
+nix/result*
+/result*
--- a/common/build.rs
+++ b/common/build.rs
@ -7,50 +7,50 @@ use std::{
 };

 fn main() {
-    // If the env variable exists then we are building on nix, use it as hash and
-    // return. `git-lfs` check is handled by nix itself.
-    if let Some(hash) = option_env!("NIX_GIT_HASH") {
+    // If these env variables exist then we are building on nix, use them as hash
+    // and tag.
+    if let (Some(hash), Some(tag)) = (option_env!("NIX_GIT_HASH"), option_env!("NIX_GIT_TAG")) {
        create_hash_file(hash);
-        return;
-    }
-
-    // Get the current githash
-    // Note: It will compare commits. As long as the commits do not diverge from the
-    // server no version change will be detected.
-    match Command::new("git")
-        .args(&[
-            "log",
-            "-n",
-            "1",
-            "--pretty=format:%h/%cd",
-            "--date=format:%Y-%m-%d-%H:%M",
-            "--abbrev=8",
-        ])
-        .output()
-    {
-        Ok(output) => match String::from_utf8(output.stdout) {
-            Ok(hash) => {
-                create_hash_file(&hash);
+        create_tag_file(tag);
+    } else {
+        // Get the current githash
+        // Note: It will compare commits. As long as the commits do not diverge from the
+        // server no version change will be detected.
+        match Command::new("git")
+            .args(&[
+                "log",
+                "-n",
+                "1",
+                "--pretty=format:%h/%cd",
+                "--date=format:%Y-%m-%d-%H:%M",
+                "--abbrev=8",
+            ])
+            .output()
+        {
+            Ok(output) => match String::from_utf8(output.stdout) {
+                Ok(hash) => {
+                    create_hash_file(&hash);
+                },
+                Err(e) => panic!("failed to convert git output to UTF-8: {}", e),
            },
-            Err(e) => panic!("failed to convert git output to UTF-8: {}", e),
-        },
-        Err(e) => panic!("failed to retrieve current git commit hash: {}", e),
-    }
+            Err(e) => panic!("failed to retrieve current git commit hash: {}", e),
+        }

-    // Get the current githash
-    // Note: It will compare commits. As long as the commits do not diverge from the
-    // server no version change will be detected.
-    match Command::new("git")
-        .args(&["describe", "--exact-match", "--tags", "HEAD"])
-        .output()
-    {
-        Ok(output) => match String::from_utf8(output.stdout) {
-            Ok(tag) => {
-                create_tag_file(&tag);
+        // Get the current githash
+        // Note: It will compare commits. As long as the commits do not diverge from the
+        // server no version change will be detected.
+        match Command::new("git")
+            .args(&["describe", "--exact-match", "--tags", "HEAD"])
+            .output()
+        {
+            Ok(output) => match String::from_utf8(output.stdout) {
+                Ok(tag) => {
+                    create_tag_file(&tag);
+                },
+                Err(e) => panic!("failed to convert git output to UTF-8: {}", e),
            },
-            Err(e) => panic!("failed to convert git output to UTF-8: {}", e),
-        },
-        Err(e) => panic!("failed to retrieve current git commit hash: {}", e),
+            Err(e) => panic!("failed to retrieve current git commit hash: {}", e),
+        }
    }

    // Check if git-lfs is working
--- a/nix/Cargo.nix
+++ b/nix/Cargo.nix
--- a/nix/README.md
+++ b/nix/README.md
@ -1,34 +1,43 @@
 ### How to use

-To build Voxygen, run:
-`nix build`
+To build and install Voxygen and the server CLI into user profile, run:
+```shell
+nix-env -f nix/default.nix -i
+```
+You can configure what to install by changing the `cratesToBuild` argument:
+```shell
+nix-env -f nix/default.nix --arg cratesToBuild '["veloren-voxygen"]'
+```
+For example, this will install Voxygen only.

-To build another binary, run:
-`nix build --arg crateName "<binary name here>"`
-
-To enter the development shell (which includes all tools mentioned in this readme), run:
-`nix-shell shell.nix`
+To enter the development shell (which includes all tools mentioned in this readme + tools you'll need to develop Veloren), run:
+```shell
+nix-shell nix/shell.nix
+```

 ### Managing Cargo.nix

 Enter the development shell.

 To update `Cargo.nix` (and `crate-hashes.json`) using latest `Cargo.lock`, run:
-`crate2nix generate -f ../Cargo.toml`
+```shell
+crate2nix generate -f ../Cargo.toml
+```

 ### Managing dependencies

 We use [niv](https://github.com/nmattia/niv) to manage dependencies.

-Enter the development shell in repository root:
-`cd .. && nix-shell nix/shell.nix`
-
-To update the dependencies, run:
-`niv update`
+To update the dependencies, run (from repository root):
+```shell
+niv update
+```

 ### Formatting

 Use [nixfmt](https://github.com/serokell/nixfmt) to format files.

-To format every file:
-`nixfmt *.nix`
+To format every Nix file in current working directory:
+```shell
+nixfmt *.nix
+```
--- a/nix/common.nix
+++ b/nix/common.nix
@ -0,0 +1,22 @@
+{ pkgs }:
+with pkgs;
+let
+  xorgLibraries = with xorg; [ libX11 libXcursor libXrandr libXi ];
+  otherLibraries = [
+    libGL
+    # wayland
+    /* uncomment above for wayland support (?)
+       for some reason it doesn't work (triggers `unreachable!()` code in winit!)
+       so I disabled it by default
+    */
+  ];
+  neededLibPaths = lib.concatStringsSep ":"
+    (map (p: "${p}/lib") (xorgLibraries ++ otherLibraries));
+
+  crateDeps = {
+    libudev-sys = [ pkg-config libudev ];
+    alsa-sys = [ pkg-config alsaLib ];
+    veloren-network = [ pkg-config openssl ];
+    veloren-voxygen = [ atk cairo glib gtk3 pango ];
+  };
+in { inherit neededLibPaths crateDeps; }
--- a/nix/crate-hashes.json
+++ b/nix/crate-hashes.json
@ -1,14 +1,21 @@
 {
  "auth-common 0.1.0 (git+https://gitlab.com/veloren/auth.git?rev=b943c85e4a38f5ec60cd18c34c73097640162bfe#b943c85e4a38f5ec60cd18c34c73097640162bfe)": "0ckpx36a5gmzirsih03ddfyp4iz23ffwb6sc75smb4srx1ivc7fy",
  "authc 1.0.0 (git+https://gitlab.com/veloren/auth.git?rev=b943c85e4a38f5ec60cd18c34c73097640162bfe#b943c85e4a38f5ec60cd18c34c73097640162bfe)": "0ckpx36a5gmzirsih03ddfyp4iz23ffwb6sc75smb4srx1ivc7fy",
-  "conrod_core 0.63.0 (git+https://gitlab.com/veloren/conrod.git#1ab6eccf94b16a8977a3274b31d4dbfef9cf9a30)": "1xr12b422wb2ygfzn5mfbqyqp8zia2ciclxladzlan7hr5h226jc",
-  "conrod_derive 0.63.0 (git+https://gitlab.com/veloren/conrod.git#1ab6eccf94b16a8977a3274b31d4dbfef9cf9a30)": "1xr12b422wb2ygfzn5mfbqyqp8zia2ciclxladzlan7hr5h226jc",
-  "conrod_winit 0.63.0 (git+https://gitlab.com/veloren/conrod.git#1ab6eccf94b16a8977a3274b31d4dbfef9cf9a30)": "1xr12b422wb2ygfzn5mfbqyqp8zia2ciclxladzlan7hr5h226jc",
+  "conrod_core 0.63.0 (git+https://gitlab.com/veloren/conrod.git?branch=copypasta_0.7#1ae5193588fb662a7189d81edd9f2d653c7f1da0)": "14sxyw8si0c2md5p5hssvfl12368hqp1fy6ighd7v4lb8fqwp6zj",
+  "conrod_derive 0.63.0 (git+https://gitlab.com/veloren/conrod.git?branch=copypasta_0.7#1ae5193588fb662a7189d81edd9f2d653c7f1da0)": "14sxyw8si0c2md5p5hssvfl12368hqp1fy6ighd7v4lb8fqwp6zj",
+  "conrod_winit 0.63.0 (git+https://gitlab.com/veloren/conrod.git?branch=copypasta_0.7#1ae5193588fb662a7189d81edd9f2d653c7f1da0)": "14sxyw8si0c2md5p5hssvfl12368hqp1fy6ighd7v4lb8fqwp6zj",
  "euc 0.5.1 (git+https://github.com/zesterer/euc.git#c9a7c17a03d45fce00caeeca09afa1e1558cd183)": "0qvk0bx1arkgmdc59sip39zszdw2fwv6jcy5jinv18n5m1nrclw4",
-  "guillotiere 0.4.2 (git+https://github.com/Imberflur/guillotiere#42c298f5bcf0f95f1a004360d05e25ca3711e9ed)": "1knqbn777f3cgzbsaqawzclgrqf3nav6x3gjzc2hsls3acccx1ya",
-  "msgbox 0.4.0 (git+https://github.com/bekker/msgbox-rs.git?rev=68fe39a#68fe39a60019b38a1569ae4e9ed796a0f0542673)": "18h6s50n7mz2ggfishhi91p2298shqhzx5xagpg9q4zb4y90c2wr",
+  "iced_core 0.2.1 (git+https://github.com/hecrj/iced?rev=f464316#f46431600cb61d4e83e0ded1ca79525478436be3)": "08ixcznfi6wmznjyg0ahi9zs12x5mlbw1bznifqr66gkpa25kyp1",
+  "iced_futures 0.1.2 (git+https://github.com/hecrj/iced?rev=f464316#f46431600cb61d4e83e0ded1ca79525478436be3)": "08ixcznfi6wmznjyg0ahi9zs12x5mlbw1bznifqr66gkpa25kyp1",
+  "iced_graphics 0.1.0 (git+https://github.com/hecrj/iced?rev=f464316#f46431600cb61d4e83e0ded1ca79525478436be3)": "08ixcznfi6wmznjyg0ahi9zs12x5mlbw1bznifqr66gkpa25kyp1",
+  "iced_native 0.2.2 (git+https://github.com/hecrj/iced?rev=f464316#f46431600cb61d4e83e0ded1ca79525478436be3)": "08ixcznfi6wmznjyg0ahi9zs12x5mlbw1bznifqr66gkpa25kyp1",
+  "iced_style 0.1.0 (git+https://github.com/hecrj/iced?rev=f464316#f46431600cb61d4e83e0ded1ca79525478436be3)": "08ixcznfi6wmznjyg0ahi9zs12x5mlbw1bznifqr66gkpa25kyp1",
+  "iced_winit 0.1.1 (git+https://github.com/hecrj/iced?rev=f464316#f46431600cb61d4e83e0ded1ca79525478436be3)": "08ixcznfi6wmznjyg0ahi9zs12x5mlbw1bznifqr66gkpa25kyp1",
  "portpicker 0.1.0 (git+https://github.com/xMAC94x/portpicker-rs#9d6df36c53c94684080a64a7212dd6bfc3617ee4)": "00vl2k3xfihxq86kf5rsknjl8dxmrxqhwajwn0hj4gzgnbssr0rx",
+  "scan_fmt 0.2.5 (git+https://github.com/Imberflur/scan_fmt#5f9e8eed73e93e8d19fa864d76e75bb4984cffe7)": "1g36jm3rii6iziqpddszhdk6bqpa7jzsbmrlfzmsmi16zcisrvid",
  "specs 0.16.1 (git+https://github.com/amethyst/specs.git?rev=7a2e348ab2223818bad487695c66c43db88050a5#7a2e348ab2223818bad487695c66c43db88050a5)": "1z7gjiq7zirg9az3ly1y2ghi5m7s3x1bp35gw5x0cyv50fsi3pjq",
  "specs-idvs 0.1.0 (git+https://gitlab.com/veloren/specs-idvs.git?branch=specs-git#fcb0b2306b571f62f9f85d89e79e087454d95efd)": "00w4kc60d7mjb5gbkcxrxzarshmhf4idqm3sk8335f7s3pn9q0s5",
-  "winit 0.22.2 (git+https://github.com/Imberflur/winit.git?branch=macos-test#e98133adf2abbfc4368f6c069d0beb2b8b688b42)": "0hv9wfsn1d5fwrs37vqyazrwys8665q03m9sygk2kal1jbl3x8zj"
+  "tui 0.10.0 (git+https://github.com/fdehau/tui-rs.git?branch=paragraph-scroll#54b841fab6cfdb38e8dc1382176e965787964b4c)": "0si3sp0hkjjrrfvmiynhai35pgjlnflw7qwwh268rpivdl8bd9xz",
+  "vek 0.12.0 (git+https://gitlab.com/veloren/vek.git?branch=fix_intrinsics#237a78528b505f34f6dde5dc77db3b642388fe4a)": "1v3kxjl826zf0zbi9pbwpw75ybidr0cdsgx772l0671zmp3yrkjg",
+  "winit 0.23.0 (git+https://gitlab.com/veloren/winit.git?branch=macos-test-spiffed#7c8c5f21384c898f50d37298d229093549b08803)": "1amfl8xpmyh7a4sy87iz5rybdgfn598crl6y6hxyrmyamg6cbqd4"
 }
--- a/nix/default.nix
+++ b/nix/default.nix
@ -1,13 +1,39 @@
-{ crateName ? "veloren-voxygen",
-# `crate2nix` doesn't support profiles in `Cargo.toml`, so default to release. Otherwise bad performance (non-release is built with opt level 0)
-release ? true, nixpkgs ? <nixpkgs>, system ? builtins.currentSystem
+{
+/* `crate2nix` doesn't support profiles in `Cargo.toml`, so default to release.
+   Otherwise bad performance (non-release is built with opt level 0)
+*/
+release ? true, cratesToBuild ? [ "veloren-voxygen" "veloren-server-cli" ]
+, system ? builtins.currentSystem
 , sources ? import ./sources.nix { inherit system; } }:

 let
-  gitHash =
-    # Check if git-lfs is working.
+  isBuildingCrate = name:
+    builtins.any (otherName: name == otherName) cratesToBuild;
+  isBuildingVoxygen = isBuildingCrate "veloren-voxygen";
+  isBuildingServerCli = isBuildingCrate "veloren-server-cli";
+
+  pkgs = import ./nixpkgs.nix { inherit sources system; };
+  common = import ./common.nix { inherit pkgs; };
+
+  meta = with pkgs; {
+    description = "Veloren is a multiplayer voxel RPG written in Rust.";
+    longDescription = ''
+      Veloren is a multiplayer voxel RPG written in Rust.
+      It is inspired by games such as Cube World, Legend of Zelda: Breath of the Wild, Dwarf Fortress and Minecraft.
+    '';
+    homepage = "https://veloren.net";
+    upstream = "https://gitlab.com/veloren/veloren";
+    license = lib.licenses.gpl3;
+    maintainers = [ lib.maintainers.yusdacra ];
+    platforms = lib.platforms.all;
+  };
+
+  makeGitCommand = subcommands: name:
+    # Check if git-lfs is working. This is a partial check only,
+    # the actual check is done in `common/build.rs`. We do this
+    # so that the build fails early.
    if builtins.pathExists ../assets/voxygen/background/bg_main.png then
-      builtins.readFile (pkgs.runCommand "getGitHash" { } ''
+      builtins.readFile (pkgs.runCommand name { } ''
        cd ${
        # Only copy the `.git` directory to nix store, anything else is a waste.
          builtins.path {
@ -16,7 +42,7 @@ let
            name = "git";
          }
        }
-        ${pkgs.git}/bin/git log -n 1 --pretty=format:%h/%cd --date=format:%Y-%m-%d-%H:%M --abbrev=8 > $out
+        ${pkgs.git}/bin/git ${subcommands} > $out
      '')
    else
      abort ''
@ -28,23 +54,80 @@ let
        See the book at https://book.veloren.net/ for details.
      '';

-  pkgs = import ./nixpkgs.nix { inherit sources nixpkgs system; };
+  gitHash = makeGitCommand
+    "log -n 1 --pretty=format:%h/%cd --date=format:%Y-%m-%d-%H:%M --abbrev=8"
+    "getGitHash";

-  veloren = with pkgs;
+  gitTag =
+    # If the git command errors out we feed an empty string
+    makeGitCommand "describe --exact-match --tags HEAD || printf ''"
+    "getGitTag";
+
+  version = if gitTag != "" then gitTag else gitHash;
+
+  veloren-crates = with pkgs;
    callPackage ./Cargo.nix {
-      defaultCrateOverrides = defaultCrateOverrides // {
-        libudev-sys = _: { buildInputs = [ pkg-config libudev ]; };
-        alsa-sys = _: { buildInputs = [ pkg-config alsaLib ]; };
-        veloren-common = _: { NIX_GIT_HASH = gitHash; };
-        veloren-network = _: { buildInputs = [ pkg-config openssl ]; };
-        veloren-voxygen = _: {
-          buildInputs = [ atk cairo glib gtk3 pango ];
-          nativeBuildInputs = [ makeWrapper ];
-          postInstall = ''
-            wrapProgram $out/bin/veloren-voxygen --set LD_LIBRARY_PATH ${xorg.libX11}/lib
-          '';
+      defaultCrateOverrides = with common;
+        defaultCrateOverrides // {
+          libudev-sys = _: { buildInputs = crateDeps.libudev-sys; };
+          alsa-sys = _: { buildInputs = crateDeps.alsa-sys; };
+          veloren-common = _:
+            (if isBuildingServerCli then {
+              DISABLE_GIT_LFS_CHECK = true;
+            } else
+              { }) // {
+                # Declare env values here so that `common/build.rs` sees them
+                NIX_GIT_HASH = gitHash;
+                NIX_GIT_TAG = gitTag;
+              };
+          veloren-network = _: { buildInputs = crateDeps.veloren-network; };
+          veloren-server-cli = _: { VELOREN_USERDATA_STRATEGY = "system"; };
+          veloren-voxygen = _: {
+            VELOREN_USERDATA_STRATEGY = "system";
+            buildInputs = crateDeps.veloren-voxygen;
+            nativeBuildInputs = [ makeWrapper ];
+            postInstall = ''
+              wrapProgram $out/bin/veloren-voxygen --set LD_LIBRARY_PATH ${neededLibPaths}
+            '';
+          };
        };
-      };
-      inherit release pkgs nixpkgs;
+      inherit release pkgs;
    };
-in veloren.workspaceMembers."${crateName}".build
+
+  veloren-assets = pkgs.symlinkJoin {
+    inherit version;
+    name = "veloren-assets_${version}";
+    paths = [
+      (pkgs.runCommand "mkVelorenAssetsDir" { } ''
+        mkdir -p $out/share/veloren
+        ln -sf ${../assets} $out/share/veloren/assets
+      '')
+    ];
+    meta = meta // {
+      longDescription = ''
+        ${meta.longDescription}
+        This package includes the assets.
+      '';
+    };
+  };
+
+  makePkg = name:
+    pkgs.symlinkJoin {
+      inherit version;
+      name = "${name}_${version}";
+      paths = [ veloren-crates.workspaceMembers."${name}".build ];
+      meta = meta // {
+        longDescription = ''
+          ${meta.longDescription}
+          ${if isBuildingVoxygen then
+            "This package includes the client, Voxygen."
+          else
+            ""}
+          ${if isBuildingServerCli then
+            "This package includes the server CLI."
+          else
+            ""}
+        '';
+      };
+    };
+in (pkgs.lib.genAttrs cratesToBuild makePkg) // { inherit veloren-assets; }
--- a/nix/nixpkgs.nix
+++ b/nix/nixpkgs.nix
@ -1,5 +1,5 @@
-{ nixpkgs ? <nixpkgs>, system ? builtins.currentSystem
-, sources ? import ./sources.nix { inherit system; } }:
+{ system, sources ? import ./sources.nix { inherit system; }
+, nixpkgs ? sources.nixpkgs }:

 let
  mozPkgs = import "${sources.nixpkgsMoz}/package-set.nix" {
@ -7,14 +7,15 @@ let
  };
  rustChannel = mozPkgs.rustChannelOf {
    rustToolchain = ../rust-toolchain;
-    sha256 = "sha256-hKjJt5RAI9cf55orvwGEkOXIGOaySX5dD2aj3iQ/IDs=";
+    hash = "sha256-P4FTKRe0nM1FRDV0Q+QY2WcC8M9IR7aPMMLWDfv+rEk=";
  };
 in import nixpkgs {
  inherit system;
  overlays = [
    (self: super: {
      rustc = rustChannel.rust;
-      inherit (rustChannel) cargo rust rust-std rust-src;
+      inherit (rustChannel)
+      ;
    })
  ];
 }
--- a/nix/shell.nix
+++ b/nix/shell.nix
@ -1,30 +1,15 @@
 { nixpkgs ? <nixpkgs>, sources ? import ./sources.nix { }
 , system ? builtins.currentSystem }:
-
 let
  pkgs = import ./nixpkgs.nix { inherit sources nixpkgs system; };
-  crate2nix = import sources.crate2nix { inherit pkgs; };
-in pkgs.mkShell {
+  common = import ./common.nix { inherit pkgs; };
+  crate2nix = pkgs.callPackage sources.crate2nix { inherit pkgs; };
+in with pkgs;
+mkShell {
  name = "veloren-shell";
-  nativeBuildInputs = with pkgs; [
-    pkg-config
-    python3
-    git
-    git-lfs
-    niv
-    nixfmt
-    crate2nix
-    cargo
-    rustc
-  ];
-  buildInputs = with pkgs; [
-    alsaLib
-    atk
-    cairo
-    glib
-    gtk3
-    libudev
-    openssl
-    pango
-  ];
+  nativeBuildInputs = [ git git-lfs niv nixfmt crate2nix cargo rustc ];
+  buildInputs = lib.concatLists (lib.attrValues common.crateDeps);
+  shellHook = ''
+    export LD_LIBRARY_PATH=${common.neededLibPaths}
+  '';
 }
--- a/nix/sources.json
+++ b/nix/sources.json
@ -5,10 +5,22 @@
        "homepage": "",
        "owner": "kolloch",
        "repo": "crate2nix",
-        "rev": "602223cdd990f17edb7bd8587a44b9ba76f8e886",
-        "sha256": "1jvhi0crlgr570365w024xysx3myflaj0yqk8hx4nz6agvrpb0hc",
+        "rev": "df3e4e6570c1058d947d70876712209a1eca6731",
+        "sha256": "1kn98ckf2h4j3xmc50n6904p5g226qa1c1jgha511d9l6lgks24r",
        "type": "tarball",
-        "url": "https://github.com/kolloch/crate2nix/archive/602223cdd990f17edb7bd8587a44b9ba76f8e886.tar.gz",
+        "url": "https://github.com/kolloch/crate2nix/archive/df3e4e6570c1058d947d70876712209a1eca6731.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "nixpkgs": {
+        "branch": "nixpkgs-unstable",
+        "description": "Nix Packages collection",
+        "homepage": "",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "6625284c397b44bc9518a5a1567c1b5aae455c08",
+        "sha256": "1w0czzv53sg35gp7sr506facbmzd33jm34p6cg23fb9kz5rf5c89",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs/archive/6625284c397b44bc9518a5a1567c1b5aae455c08.tar.gz",
        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
    },
    "nixpkgsMoz": {
@ -17,10 +29,10 @@
        "homepage": null,
        "owner": "mozilla",
        "repo": "nixpkgs-mozilla",
-        "rev": "efda5b357451dbb0431f983cca679ae3cd9b9829",
-        "sha256": "11wqrg86g3qva67vnk81ynvqyfj0zxk83cbrf0p9hsvxiwxs8469",
+        "rev": "8c007b60731c07dd7a052cce508de3bb1ae849b4",
+        "sha256": "1zybp62zz0h077zm2zmqs2wcg3whg6jqaah9hcl1gv4x8af4zhs6",
        "type": "tarball",
-        "url": "https://github.com/mozilla/nixpkgs-mozilla/archive/efda5b357451dbb0431f983cca679ae3cd9b9829.tar.gz",
+        "url": "https://github.com/mozilla/nixpkgs-mozilla/archive/8c007b60731c07dd7a052cce508de3bb1ae849b4.tar.gz",
        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
    }
 }
--- a/nix/sources.nix
+++ b/nix/sources.nix
@ -1,22 +1,26 @@
 # This file has been generated by Niv.
-{ system ? builtins.currentSystem }:
+
 let

  #
  # The fetchers. fetch_<type> fetches specs of type <type>.
  #

-  fetch_file = pkgs: spec:
-    if spec.builtin or true then
-      builtins_fetchurl { inherit (spec) url sha256; }
+  fetch_file = pkgs: name: spec:
+    let name' = sanitizeName name + "-src";
+    in if spec.builtin or true then
+      builtins_fetchurl {
+        inherit (spec) url sha256;
+        name = name';
+      }
    else
-      pkgs.fetchurl { inherit (spec) url sha256; };
+      pkgs.fetchurl {
+        inherit (spec) url sha256;
+        name = name';
+      };

  fetch_tarball = pkgs: name: spec:
-    let
-      ok = str: !builtins.isNull (builtins.match "[a-zA-Z0-9+-._?=]" str);
-      # sanitize the name, though nix will still fail if name starts with period
-      name' = stringAsChars (x: if !ok x then "-" else x) "${name}-src";
+    let name' = sanitizeName name + "-src";
    in if spec.builtin or true then
      builtins_fetchTarball {
        name = name';
@ -28,10 +32,21 @@ let
        inherit (spec) url sha256;
      };

-  fetch_git = spec:
-    builtins.fetchGit {
+  fetch_git = name: spec:
+    let
+      ref = if spec ? ref then
+        spec.ref
+      else if spec ? branch then
+        "refs/heads/${spec.branch}"
+      else if spec ? tag then
+        "refs/tags/${spec.tag}"
+      else
+        abort
+        "In git source '${name}': Please specify `ref`, `tag` or `branch`!";
+    in builtins.fetchGit {
      url = spec.repo;
-      inherit (spec) rev ref;
+      inherit (spec) rev;
+      inherit ref;
    };

  fetch_local = spec: spec.path;
@ -50,18 +65,25 @@ let
  # Various helpers
  #

+  # https://github.com/NixOS/nixpkgs/pull/83241/files#diff-c6f540a4f3bfa4b0e8b6bafd4cd54e8bR695
+  sanitizeName = name:
+    (concatMapStrings (s: if builtins.isList s then "-" else s)
+      (builtins.split "[^[:alnum:]+._?=-]+"
+        ((x: builtins.elemAt (builtins.match "\\.*(.*)" x) 0) name)));
+
  # The set of packages used when specs are fetched using non-builtins.
-  mkPkgs = sources:
+  mkPkgs = sources: system:
    let
-      sourcesNixpkgs =
-        import (builtins_fetchTarball { inherit (sources.nixpkgs) url sha256; })
-        { };
+      sourcesNixpkgs = import
+        (builtins_fetchTarball { inherit (sources.nixpkgs) url sha256; }) {
+          inherit system;
+        };
      hasNixpkgsPath = builtins.any (x: x.prefix == "nixpkgs") builtins.nixPath;
      hasThisAsNixpkgsPath = <nixpkgs> == ./.;
    in if builtins.hasAttr "nixpkgs" sources then
      sourcesNixpkgs
    else if hasNixpkgsPath && !hasThisAsNixpkgsPath then
-      import <nixpkgs> { inherit system; }
+      import <nixpkgs> { }
    else
      abort ''
        Please specify either <nixpkgs> (through -I or NIX_PATH=nixpkgs=...) or
@ -74,11 +96,11 @@ let
    if !builtins.hasAttr "type" spec then
      abort "ERROR: niv spec ${name} does not have a 'type' attribute"
    else if spec.type == "file" then
-      fetch_file pkgs spec
+      fetch_file pkgs name spec
    else if spec.type == "tarball" then
      fetch_tarball pkgs name spec
    else if spec.type == "git" then
-      fetch_git spec
+      fetch_git name spec
    else if spec.type == "local" then
      fetch_local spec
    else if spec.type == "builtin-tarball" then
@ -89,6 +111,15 @@ let
      abort
      "ERROR: niv spec ${name} has unknown type ${builtins.toJSON spec.type}";

+  # If the environment variable NIV_OVERRIDE_${name} is set, then use
+  # the path directly as opposed to the fetched source.
+  replace = name: drv:
+    let
+      saneName = stringAsChars
+        (c: if isNull (builtins.match "[a-zA-Z0-9]" c) then "_" else c) name;
+      ersatz = builtins.getEnv "NIV_OVERRIDE_${saneName}";
+    in if ersatz == "" then drv else ersatz;
+
  # Ports of functions for older nix versions

  # a Nix version of mapAttrs if the built-in doesn't exist
@ -112,21 +143,27 @@ let

  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L269
  stringAsChars = f: s: concatStrings (map f (stringToCharacters s));
+  concatMapStrings = f: list: concatStrings (map f list);
  concatStrings = builtins.concatStringsSep "";

+  # https://github.com/NixOS/nixpkgs/blob/8a9f58a375c401b96da862d969f66429def1d118/lib/attrsets.nix#L331
+  optionalAttrs = cond: as: if cond then as else { };
+
  # fetchTarball version that is compatible between all the versions of Nix
-  builtins_fetchTarball = { url, name, sha256 }@attrs:
+  builtins_fetchTarball = { url, name ? null, sha256 }@attrs:
    let inherit (builtins) lessThan nixVersion fetchTarball;
    in if lessThan nixVersion "1.12" then
-      fetchTarball { inherit name url; }
+      fetchTarball
+      ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; }))
    else
      fetchTarball attrs;

  # fetchurl version that is compatible between all the versions of Nix
-  builtins_fetchurl = { url, sha256 }@attrs:
+  builtins_fetchurl = { url, name ? null, sha256 }@attrs:
    let inherit (builtins) lessThan nixVersion fetchurl;
    in if lessThan nixVersion "1.12" then
-      fetchurl { inherit url; }
+      fetchurl
+      ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; }))
    else
      fetchurl attrs;

@ -137,18 +174,24 @@ let
        abort
        "The values in sources.json should not have an 'outPath' attribute"
      else
-        spec // { outPath = fetch config.pkgs name spec; }) config.sources;
+        spec // { outPath = replace name (fetch config.pkgs name spec); })
+    config.sources;

  # The "config" used by the fetchers
-  mkConfig = { sourcesFile ? ./sources.json
-    , sources ? builtins.fromJSON (builtins.readFile sourcesFile)
-    , pkgs ? mkPkgs sources }: rec {
+  mkConfig = { sourcesFile ?
+      if builtins.pathExists ./sources.json then ./sources.json else null
+    , sources ? if isNull sourcesFile then
+      { }
+    else
+      builtins.fromJSON (builtins.readFile sourcesFile)
+    , system ? builtins.currentSystem, pkgs ? mkPkgs sources system }: rec {
      # The sources, i.e. the attribute set of spec name to spec
      inherit sources;

      # The "pkgs" (evaluated nixpkgs) to use for e.g. non-builtin fetchers
      inherit pkgs;
    };
+
 in mkSources (mkConfig { }) // {
  __functor = _: settings: mkSources (mkConfig settings);
 }