Add experimental flake example

examples/flake/arion-compose.nix

@@ -0,0 +1,19 @@
+{ pkgs, ... }:
+{
+  config.project.name = "webapp";
+  config.services = {
+
+    webserver = {
+      service.useHostStore = true;
+      service.command = [ "sh" "-c" ''
+                  cd "$$WEB_ROOT"
+                  ${pkgs.python3}/bin/python -m http.server
+                '' ];
+      service.ports = [
+        "8000:8000" # host:container
+      ];
+      service.environment.WEB_ROOT = "${pkgs.nix.doc}/share/doc/nix/manual";
+      service.stop_signal = "SIGINT";
+    };
+  };
+}

examples/flake/arion-pkgs.nix

@@ -0,0 +1,13 @@
+let
+  flake = if builtins ? getFlake
+    then (builtins.getFlake (toString ./.)).pkgs
+    else (import flake-compat { src = ./.; }).defaultNix;
+  # NB: this is lazy
+  lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+  inherit (lock.nodes.flake-compat.locked) owner repo rev narHash;
+  flake-compat = builtins.fetchTarball {
+    url = "https://github.com/${owner}/${repo}/archive/${rev}.tar.gz";
+    sha256 = narHash;
+  };
+in
+  flake.pkgs

examples/flake/flake.lock

@@ -0,0 +1,44 @@
+{
+  "nodes": {
+    "flake-compat": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1606424373,
+        "narHash": "sha256-oq8d4//CJOrVj+EcOaSXvMebvuTkmBJuT5tzlfewUnQ=",
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "rev": "99f1c2157fba4bfe6211a321fd0ee43199025dbf",
+        "type": "github"
+      },
+      "original": {
+        "owner": "edolstra",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1618853290,
+        "narHash": "sha256-K4fddnrGOcKL+6CEchRrVmepiwvwvHxB87goqBTI5Bs=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "9a1672105db0eebe8ef59f310397435f2d0298d0",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-20.09",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

examples/flake/flake.nix

@@ -0,0 +1,19 @@
+{
+  description = "A very basic flake";
+
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-20.09";
+  inputs.flake-compat.url = "github:edolstra/flake-compat";
+  inputs.flake-compat.flake = false;
+
+  outputs = { self, nixpkgs, ... }: {
+
+    pkgs = nixpkgs.legacyPackages.x86_64-linux;
+    # # alternative:
+    # pkgs = import nixpkgs { config = { }; overlays = [ ]; system = "x86_64-linux"; };
+
+    packages.x86_64-linux.hello = nixpkgs.legacyPackages.x86_64-linux.hello;
+
+    defaultPackage.x86_64-linux = self.packages.x86_64-linux.hello;
+
+  };
+}

tests/arion-test/default.nix

@@ -57,6 +57,20 @@ in
         )
         machine.wait_until_fails("curl --fail localhost:8000")
 
+    # Tests
+    #  - examples/flake
+    # This _test_ doesn't work because flake-compat fetches the github
+    # tarballs without sha256 and/or Nix doesn't consult the store before
+    # downloading.
+    # See https://github.com/edolstra/flake-compat/pull/12
+    # with subtest("flake"):
+    #     machine.succeed(
+    #         "rm -rf work && cp -frT ''${../../examples/flake} work && cd work && NIX_PATH= arion up -d"
+    #     )
+    #     machine.wait_until_succeeds("curl --fail localhost:8000")
+    #     machine.succeed("cd work && NIX_PATH= arion down")
+    #     machine.wait_until_fails("curl --fail localhost:8000")
+
     # Tests
     #  - arion exec
     #  - examples/full-nixos