Convert to flake

core/WORKSPACE

@@ -47,7 +47,7 @@ nixpkgs_local_repository(
     nix_file_content = "import ./nixpkgs.nix",
     nix_file_deps = [
         "//:nixpkgs.nix",
-        "//:nixpkgs.json",
+        "//:flake.lock",
     ],
 )
 
@@ -72,7 +72,7 @@ nixpkgs_package(
 nixpkgs_package(
     name = "expr-test",
     nix_file_content = "let pkgs = import <nixpkgs> { config = {}; overlays = []; }; in pkgs.hello",
-    nix_file_deps = ["//:nixpkgs.json"],
+    nix_file_deps = ["//:flake.lock"],
     # Deliberately not @nixpkgs, to test whether explict file works.
     repositories = {"nixpkgs": "//:nixpkgs.nix"},
 )
@@ -141,7 +141,7 @@ nixpkgs_package(
     attribute_path = "hello",
     nix_file = "//tests:relative_imports.nix",
     nix_file_deps = [
-        "//:nixpkgs.json",
+        "//:flake.lock",
         "//:nixpkgs.nix",
         "//tests:relative_imports/nixpkgs.nix",
     ],
@@ -155,7 +155,7 @@ nixpkgs_package(
     attribute_path = "",
     nix_file_content = """let pkgs = import <nixpkgs> { config = {}; overlays = []; }; in pkgs.writeText "foo" "bar" """,
     nix_file_deps = [
-        "//:nixpkgs.json",
+        "//:flake.lock",
         "//:nixpkgs.nix",
         "//tests:relative_imports/nixpkgs.nix",
     ],

core/docs/dependencies_2.bzl

@@ -17,7 +17,7 @@ def docs_dependencies_2():
     nixpkgs_local_repository(
         name = "nixpkgs",
         nix_file = "@rules_nixpkgs_core//:nixpkgs.nix",
-        nix_file_deps = ["@rules_nixpkgs_core//:nixpkgs.json"],
+        nix_file_deps = ["@rules_nixpkgs_core//:flake.lock"],
     )
 
     rules_sh_dependencies()

core/nixpkgs.nix

@@ -1,9 +1,11 @@
 let
-  # nixpkgs 21.11
-  spec = builtins.fromJSON (builtins.readFile ./nixpkgs.json);
-  nixpkgs = fetchTarball {
-    url = "https://github.com/${spec.owner}/${spec.repo}/archive/${spec.rev}.tar.gz";
-    sha256 = spec.sha256;
-  };
+  lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+  src = lock.nodes.nixpkgs.locked;
+  nixpkgs =
+    assert src.type == "github";
+    fetchTarball {
+      url = "https://github.com/${src.owner}/${src.repo}/archive/${src.rev}.tar.gz";
+      sha256 = src.narHash;
+    };
 in
 import nixpkgs

flake.nix

@@ -0,0 +1,21 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-22.05";
+    flake-compat = {
+      url = github:edolstra/flake-compat;
+      flake = false;
+    };
+    flake-utils.url = github:numtide/flake-utils;
+  };
+  outputs = { nixpkgs, flake-utils, ... }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs { inherit system; };
+      in
+      {
+        devShells.default = with pkgs; mkShell {
+          name = "rules_nixpkgs_shell";
+          packages = [ bazel_5 bazel-buildtools cacert gcc nix git ];
+        };
+      });
+}

shell.nix

@@ -1,11 +1,11 @@
-{ pkgs ? import ./core/nixpkgs.nix {
-  config = { };
-  overlays = [ ];
-} }:
+(import
+  (
+    let lock = builtins.fromJSON (builtins.readFile ./flake.lock); in
+    fetchTarball {
+      url = "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+      sha256 = lock.nodes.flake-compat.locked.narHash;
+    }
+  )
+  { src = ./.; }
+).shellNix
 
-with pkgs;
-
-mkShell {
-  name = "rules_nixpkgs_shell";
-  packages = [ bazel_5 bazel-buildtools cacert gcc nix git ];
-}