Merge nixpkgs.config and nixpkgs.overlays

This replaces #12, and allows for Nixpkgs overlays and config to be overridden
in machine configs. With #12, overlays set in machine configurations
(`nixpkgs.overlays`) get silently ignored.

src/nix/eval.nix

@@ -243,9 +243,28 @@ let
           in "Exactly one of `${prefix}.text`, `${prefix}.keyCommand` and `${prefix}.keyFile` must be set.";
         }) config.deployment.keys;
     };
+
+    # Here we need to merge the configurations in meta.nixpkgs
+    # and in machine config.
+    nixpkgsModule = { config, lib, ... }: {
+      nixpkgs.overlays = lib.mkBefore npkgs.overlays;
+      nixpkgs.config = lib.mkOptionDefault npkgs.config;
+
+      # The merging of nixpkgs.config seems to be broken.
+      # Let's warn the user if not all config attributes set in
+      # meta.nixpkgs are overridden.
+      warnings = let
+        metaKeys = attrNames npkgs.config;
+        nodeKeys = attrNames config.nixpkgs.config;
+        remainingKeys = filter (k: ! elem k nodeKeys) metaKeys;
+      in
+        lib.optional (length remainingKeys != 0)
+        "The following Nixpkgs configuration keys set in meta.nixpkgs will be ignored: ${toString remainingKeys}";
+    };
   in evalConfig {
     modules = [
       assertionModule
+      nixpkgsModule
       deploymentOptions
       hive.defaults
       config
@@ -253,7 +272,6 @@ let
     specialArgs = {
       inherit name nodes;
       modulesPath = npkgs.path + "/nixos/modules";
-      pkgs = npkgs;
     };
   };
 

src/nix/tests.rs

@@ -1,6 +1,7 @@
 //! Integration-ish tests
 
 use super::*;
+use crate::progress::TaskProgress;
 
 use std::collections::HashSet;
 use std::hash::Hash;
@@ -56,6 +57,22 @@ impl TempHive {
         let hive = Self::new(text);
         assert!(block_on(hive.deployment_info()).is_err());
     }
+
+    /// Asserts that the specified nodes can be fully evaluated.
+    pub fn eval_success(text: &str, nodes: Vec<String>) {
+        let hive = Self::new(text);
+        let progress = TaskProgress::new("tests".to_string(), 5);
+        let (profiles, _) = block_on(hive.eval_selected(&nodes, progress));
+        assert!(profiles.is_ok());
+    }
+
+    /// Asserts that the specified nodes will fail to evaluate.
+    pub fn eval_failure(text: &str, nodes: Vec<String>) {
+        let hive = Self::new(text);
+        let progress = TaskProgress::new("tests".to_string(), 5);
+        let (profiles, _) = block_on(hive.eval_selected(&nodes, progress));
+        assert!(profiles.is_err());
+    }
 }
 
 impl Deref for TempHive {
@@ -210,3 +227,149 @@ fn test_parse_key_file() {
       }
     "#);
 }
+
+#[test]
+fn test_eval_non_existent_pkg() {
+    // Sanity check
+    TempHive::eval_failure(r#"
+      {
+        test = { pkgs, ... }: {
+          boot.isContainer = true;
+          environment.systemPackages = with pkgs; [ thisPackageDoesNotExist ];
+        };
+      }
+    "#, vec![ "test".to_string() ]);
+}
+
+// Nixpkgs config tests
+
+#[test]
+fn test_nixpkgs_overlay_meta_nixpkgs() {
+    // Only set overlays in meta.nixpkgs
+    TempHive::eval_success(r#"
+      {
+        meta = {
+          nixpkgs = import <nixpkgs> {
+            overlays = [
+              (self: super: { my-coreutils = super.coreutils; })
+            ];
+          };
+        };
+        test = { pkgs, ... }: {
+          boot.isContainer = true;
+          environment.systemPackages = with pkgs; [ my-coreutils ];
+        };
+      }
+    "#, vec![ "test".to_string() ]);
+}
+
+#[test]
+fn test_nixpkgs_overlay_node_config() {
+    // Only set overlays in node config
+    TempHive::eval_success(r#"
+      {
+        test = { pkgs, ... }: {
+          boot.isContainer = true;
+          nixpkgs.overlays = [
+            (self: super: { my-coreutils = super.coreutils; })
+          ];
+          environment.systemPackages = with pkgs; [ my-coreutils ];
+        };
+      }
+    "#, vec![ "test".to_string() ]);
+}
+
+#[test]
+fn test_nixpkgs_overlay_both() {
+    // Set overlays both in meta.nixpkgs and in node config
+    TempHive::eval_success(r#"
+      {
+        meta = {
+          nixpkgs = import <nixpkgs> {
+            overlays = [
+              (self: super: { meta-coreutils = super.coreutils; })
+            ];
+          };
+        };
+        test = { pkgs, ... }: {
+          boot.isContainer = true;
+          nixpkgs.overlays = [
+            (self: super: { node-busybox = super.busybox; })
+          ];
+          environment.systemPackages = with pkgs; [ meta-coreutils node-busybox ];
+        };
+      }
+    "#, vec![ "test".to_string() ]);
+}
+
+#[test]
+fn test_nixpkgs_config_meta_nixpkgs() {
+    // Set config in meta.nixpkgs
+    TempHive::eval_success(r#"
+      {
+        meta = {
+          nixpkgs = import <nixpkgs> {
+            config = {
+              allowUnfree = true;
+            };
+          };
+        };
+        test = { pkgs, ... }: {
+          boot.isContainer = assert pkgs.config.allowUnfree; true;
+        };
+      }
+    "#, vec![ "test".to_string() ]);
+}
+
+#[test]
+fn test_nixpkgs_config_node_config() {
+    // Set config in node config
+    TempHive::eval_success(r#"
+      {
+        test = { pkgs, ... }: {
+          nixpkgs.config = {
+            allowUnfree = true;
+          };
+          boot.isContainer = assert pkgs.config.allowUnfree; true;
+        };
+      }
+    "#, vec![ "test".to_string() ]);
+}
+
+#[test]
+fn test_nixpkgs_config_override() {
+    // Set same config both in meta.nixpkgs and in node config
+    let template = r#"
+      {
+        meta = {
+          nixpkgs = import <nixpkgs> {
+            config = {
+              allowUnfree = META_VAL;
+            };
+          };
+        };
+        test = { pkgs, ... }: {
+          nixpkgs.config = {
+            allowUnfree = NODE_VAL;
+          };
+          boot.isContainer = assert pkgs.config.allowUnfree == EXPECTED_VAL; true;
+        };
+      }
+    "#;
+
+    TempHive::eval_success(
+        &template
+            .replace("META_VAL", "true")
+            .replace("NODE_VAL", "false")
+            .replace("EXPECTED_VAL", "false"),
+        vec![ "test".to_string() ]
+    );
+
+    TempHive::eval_success(
+        &template
+            .replace("META_VAL", "false")
+            .replace("NODE_VAL", "true")
+            .replace("EXPECTED_VAL", "true"),
+        vec![ "test".to_string() ]
+    );
+}