modules/test: move test derivation to an option

Introduced the `test.derivation` read-only option.

flake-modules/lib.nix

@@ -6,12 +6,6 @@
 }:
 {
   flake.lib = lib.genAttrs config.systems (
-    lib.flip withSystem (
-      { pkgs, config, ... }:
-      import ../lib {
-        inherit pkgs lib;
-        inherit (config.legacyPackages) makeNixvimWithModule;
-      }
-    )
+    lib.flip withSystem ({ pkgs, ... }: import ../lib { inherit pkgs lib; })
   );
 }

flake-modules/tests.nix

@@ -10,8 +10,7 @@
       ...
     }:
     {
-      checks =
-        {
+      checks = {
         extra-args-tests = import ../tests/extra-args.nix {
           inherit pkgs;
           inherit makeNixvimWithModule;
@@ -40,14 +39,6 @@
         maintainers = import ../tests/maintainers.nix { inherit pkgs; };
 
         generated = pkgs.callPackage ../tests/generated.nix { };
-        }
-        // (import ../tests {
-          inherit
-            pkgs
-            pkgsUnfree
-            helpers
-            makeNixvimWithModule
-            ;
-        });
+      } // import ../tests { inherit pkgs pkgsUnfree helpers; };
     };
 }

lib/default.nix

@@ -1,6 +1,5 @@
 # Args probably only needs pkgs and lib
 {
-  makeNixvimWithModule,
   pkgs,
   lib ? pkgs.lib,
   _nixvimTests ? false,
@@ -8,6 +7,6 @@
 }@args:
 {
   # Add all exported modules here
-  check = import ../tests/test-derivation.nix { inherit makeNixvimWithModule lib pkgs; };
+  check = import ../tests/test-derivation.nix { inherit lib pkgs; };
   helpers = import ./helpers.nix (args // { inherit _nixvimTests; });
 }

lib/modules.nix

@@ -23,7 +23,7 @@ rec {
       modules ? [ ],
       extraSpecialArgs ? { },
       # Set to false to disable warnings and assertions
-      # Intended for use with tests, where we may not want to check assertions
+      # Intended to aid accessing config.test.derivation
       # WARNING: This argument may be removed without notice:
       check ? true,
     }:

modules/top-level/test.nix

@@ -1,10 +1,64 @@
-{ lib, ... }:
+{
+  pkgs,
+  config,
+  lib,
+  ...
+}:
+let
+  cfg = config.test;
+in
 {
   options.test = {
+    name = lib.mkOption {
+      type = lib.types.str;
+      default = "nixvim-check";
+      description = "The test derivation's name.";
+    };
+
     runNvim = lib.mkOption {
       type = lib.types.bool;
       description = "Whether to run `nvim` in the test.";
       default = true;
     };
+
+    # Output
+    derivation = lib.mkOption {
+      type = lib.types.package;
+      description = ''
+        A derivation that tests the config by running neovim.
+      '';
+      readOnly = true;
+    };
+  };
+
+  config = {
+    test.derivation = pkgs.stdenv.mkDerivation {
+      inherit (cfg) name;
+      dontUnpack = true;
+
+      nativeBuildInputs = [
+        config.finalPackage
+        pkgs.docker-client
+      ];
+
+      # We need to set HOME because neovim will try to create some files
+      #
+      # Because neovim does not return an exitcode when quitting we need to check if there are
+      # errors on stderr
+      buildPhase = lib.optionalString cfg.runNvim ''
+        mkdir -p .cache/nvim
+
+        output=$(HOME=$(realpath .) nvim -mn --headless "+q" 2>&1 >/dev/null)
+        if [[ -n $output ]]; then
+          echo "ERROR: $output"
+          exit 1
+        fi
+      '';
+
+      # If we don't do this nix is not happy
+      installPhase = ''
+        touch $out
+      '';
+    };
   };
 }

tests/default.nix

@@ -1,5 +1,4 @@
 {
-  makeNixvimWithModule,
   lib ? pkgs.lib,
   helpers,
   pkgs,
@@ -7,7 +6,7 @@
 }:
 let
   fetchTests = import ./fetch-tests.nix;
-  test-derivation = import ./test-derivation.nix { inherit pkgs lib makeNixvimWithModule; };
+  test-derivation = import ./test-derivation.nix { inherit pkgs lib; };
   inherit (test-derivation) mkTestDerivationFromNixvimModule;
 
   # List of files containing configurations

tests/test-derivation.nix

@@ -1,7 +1,6 @@
 {
   pkgs,
   lib ? pkgs.lib,
-  makeNixvimWithModule,
   ...
 }:
 let
@@ -16,46 +15,26 @@ let
       ...
     }@args:
     let
-      cfg = nvim.config.test;
-      runNvim =
-        lib.warnIf (args ? dontRun)
-          "mkTestDerivationFromNvim: the `dontRun` argument is deprecated. You should use the `test.runNvim` module option instead."
-          (cfg.runNvim && !dontRun);
-    in
-    pkgs.stdenv.mkDerivation {
+      # FIXME: this doesn't support helpers.enableExceptInTests, a context option would be better
+      result = nvim.extend {
+        config.test =
+          {
             inherit name;
-
-      nativeBuildInputs = [
-        nvim
-        pkgs.docker-client
-      ];
-
-      dontUnpack = true;
-      # We need to set HOME because neovim will try to create some files
-      #
-      # Because neovim does not return an exitcode when quitting we need to check if there are
-      # errors on stderr
-      buildPhase = lib.optionalString runNvim ''
-        mkdir -p .cache/nvim
-
-        output=$(HOME=$(realpath .) nvim -mn --headless "+q" 2>&1 >/dev/null)
-        if [[ -n $output ]]; then
-            echo "ERROR: $output"
-          exit 1
-        fi
-      '';
-
-      # If we don't do this nix is not happy
-      installPhase = ''
-        mkdir $out
-      '';
+          }
+          // lib.optionalAttrs (args ? dontRun) (
+            lib.warn
+              "mkTestDerivationFromNvim: the `dontRun` argument is deprecated. You should use the `test.runNvim` module option instead."
+              { runNvim = !dontRun; }
+          );
       };
+    in
+    result.config.test.derivation;
 
   # Create a nix derivation from a nixvim configuration.
   # The build phase simply consists in running neovim with the given configuration.
   mkTestDerivationFromNixvimModule =
     {
-      name ? "nixvim-check",
+      name ? null,
       pkgs ? pkgs,
       module,
       extraSpecialArgs ? { },
@@ -63,22 +42,29 @@ let
       dontRun ? false,
     }@args:
     let
-      nvim = makeNixvimWithModule {
-        inherit pkgs extraSpecialArgs;
+      helpers = import ../lib/helpers.nix {
+        inherit pkgs lib;
+        # TODO: deprecate helpers.enableExceptInTests,
+        # add a context option e.g. `config.isTest`?
         _nixvimTests = true;
-        module =
-          if args ? dontRun then
+      };
+
+      result = helpers.modules.evalNixvim {
+        modules = [
+          module
+          (lib.optionalAttrs (name != null) { test.name = name; })
+          (lib.optionalAttrs (args ? dontRun) (
             lib.warn
               "mkTestDerivationFromNixvimModule: the `dontRun` argument is deprecated. You should use the `test.runNvim` module option instead."
-              {
-                imports = [ module ];
-                config.test.runNvim = !dontRun;
-              }
-          else
-            module;
+              { config.test.runNvim = !dontRun; }
+          ))
+        ];
+        extraSpecialArgs = {
+          defaultPkgs = pkgs;
+        } // extraSpecialArgs;
       };
     in
-    mkTestDerivationFromNvim { inherit name nvim; };
+    result.config.test.derivation;
 in
 {
   inherit mkTestDerivationFromNvim mkTestDerivationFromNixvimModule;