modules/output: refactor config generation

The motivation for this change was to avoid generating empty
config sections like

    vim.cmd([[

    ]])

To make a config generation cleaner several helper functions introduced:

* `hasContent` have been moved to helpers
* `concatNonEmptyLines` joins strings (which has content) separated with
  newlines
* `wrapVimscriptForLua` wraps a lua string for using in Vimscript, but
  only if the string has content, otherwise empty string is returned
* `wrapLuaForVimscript` wraps Vimscript for using in lua, but only if
  the string has content, otherwise empty string is returned

Added tests:

* testing that all possible config sections are present in the final
  generated config
* testing that the config files generated by empty `files` definitions
  don't have any content in it

lib/utils.nix

@@ -4,7 +4,14 @@
   _nixvimTests,
 }:
 with lib;
-{
+rec {
+  # Whether a string contains something other than whitespaces
+  hasContent = str: builtins.match "[[:space:]]*" str == null;
+
+  # Concatenate a list of strings, adding a newline at the end of each one,
+  # but skipping strings containing only whitespace characters
+  concatNonEmptyLines = lines: concatLines (builtins.filter hasContent lines);
+
   listToUnkeyedAttrs =
     list:
     builtins.listToAttrs (lib.lists.imap0 (idx: lib.nameValuePair "__unkeyed-${toString idx}") list);
@@ -118,4 +125,26 @@ with lib;
       ${string}
     end
   '';
+
+  # Wrap Vimscript for using in lua,
+  # but only if the string contains something other than whitespaces
+  # TODO: account for a possible ']]' in the string
+  wrapVimscriptForLua =
+    string:
+    optionalString (hasContent string) ''
+      vim.cmd([[
+      ${string}
+      ]])
+    '';
+
+  # Wrap lua script for using in Vimscript,
+  # but only if the string contains something other than whitespaces
+  # TODO: account for a possible 'EOF' if the string
+  wrapLuaForVimscript =
+    string:
+    optionalString (hasContent string) ''
+      lua << EOF
+      ${string}
+      EOF
+    '';
 }

modules/output.nix

@@ -1,4 +1,9 @@
-{ lib, config, ... }:
+{
+  lib,
+  config,
+  helpers,
+  ...
+}:
 with lib;
 let
   pluginWithConfigType = types.submodule {
@@ -97,29 +102,27 @@ in
     };
   };
 
-  config =
-    let
-      contentLua = ''
-        ${config.extraConfigLuaPre}
-        vim.cmd([[
-          ${config.extraConfigVim}
-        ]])
-        ${config.extraConfigLua}
-        ${config.extraConfigLuaPost}
-      '';
-
-      contentVim = ''
-        lua << EOF
-          ${config.extraConfigLuaPre}
-        EOF
-        ${config.extraConfigVim}
-        lua << EOF
-          ${config.extraConfigLua}
-          ${config.extraConfigLuaPost}
-        EOF
-      '';
-    in
-    {
-      content = if config.type == "lua" then contentLua else contentVim;
+  config = {
+    content =
+      if config.type == "lua" then
+        # Lua
+        helpers.concatNonEmptyLines [
+          config.extraConfigLuaPre
+          (helpers.wrapVimscriptForLua config.extraConfigVim)
+          config.extraConfigLua
+          config.extraConfigLuaPost
+        ]
+      else
+        # Vimscript
+        helpers.concatNonEmptyLines [
+          (helpers.wrapLuaForVimscript config.extraConfigLuaPre)
+          config.extraConfigVim
+          (helpers.wrapLuaForVimscript (
+            helpers.concatNonEmptyLines [
+              config.extraConfigLua
+              config.extraConfigLuaPost
+            ]
+          ))
+        ];
   };
 }

modules/top-level/output.nix

@@ -107,16 +107,10 @@ with lib;
         }
       );
 
-      customRC =
-        let
-          hasContent = str: (builtins.match "[[:space:]]*" str) == null;
-        in
-        (optionalString (hasContent neovimConfig.neovimRcContent) ''
-          vim.cmd([[
-            ${neovimConfig.neovimRcContent}
-          ]])
-        '')
-        + config.content;
+      customRC = helpers.concatNonEmptyLines [
+        (helpers.wrapVimscriptForLua neovimConfig.neovimRcContent)
+        config.content
+      ];
 
       init = helpers.writeLua "init.lua" customRC;
 

tests/test-sources/modules/output.nix

@@ -4,4 +4,90 @@
     # Make sure jsregexp is in LUA_PATH
     extraConfigLua = ''require("jsregexp")'';
   };
+
+  # Test that all extraConfigs are present in output
+  all-configs.module =
+    {
+      config,
+      pkgs,
+      lib,
+      ...
+    }:
+    let
+      configs = {
+        extraConfigLuaPre = "string.format('extraConfigLuaPre1')";
+        extraConfigLua = "string.format('extraConfigLua2')";
+        extraConfigLuaPost = "string.format('extraConfigLuaPost3')";
+        extraConfigVim = "let g:var = 'extraConfigVim4'";
+      };
+      mkConfigAssertions = name: value: [
+        {
+          assertion = lib.hasInfix "extraConfigLuaPre1" value;
+          message = "Configuration file ${name} does not contain extraConfigLuaPre.";
+        }
+        {
+          assertion = lib.hasInfix "extraConfigLua2" value;
+          message = "Configuration file ${name} does not contain extraConfigLua.";
+        }
+        {
+          assertion = lib.hasInfix "extraConfigLuaPost3" value;
+          message = "Configuration file ${name} does not contain extraConfigLuaPost.";
+        }
+        {
+          assertion = lib.hasInfix "extraConfigVim4" value;
+          message = "Configuration file ${name} does not contain extraConfigVim.";
+        }
+      ];
+    in
+    configs
+    // {
+      files = {
+        "test.lua" = configs;
+        "test.vim" = configs;
+      };
+
+      # Plugin configs
+      extraPlugins = [
+        {
+          plugin = pkgs.emptyDirectory;
+          config = "let g:var = 'neovimRcContent5'";
+        }
+      ];
+
+      assertions =
+        mkConfigAssertions "init.lua" config.content
+        ++ mkConfigAssertions "test.lua" config.files."test.lua".content
+        ++ mkConfigAssertions "test.vim" config.files."test.vim".content
+        # Check the final generated init.lua too
+        ++ mkConfigAssertions "initPath" (builtins.readFile config.initPath)
+        ++ [
+          # Only init.lua contains configuration from plugin definitions
+          {
+            assertion = lib.hasInfix "neovimRcContent5" (builtins.readFile config.initPath);
+            message = "Configuration file init.lua does not contain plugin configs";
+          }
+        ];
+    };
+
+  files-default-empty.module =
+    { config, helpers, ... }:
+    {
+      files = {
+        # lua type
+        "test.lua" = { };
+        # vim type
+        "test.vim" = { };
+      };
+
+      assertions = [
+        {
+          assertion = !helpers.hasContent config.files."test.lua".content;
+          message = "Default content of test.lua file is expected to be empty.";
+        }
+        {
+          assertion = !helpers.hasContent config.files."test.vim".content;
+          message = "Default content of test.vim file is expected to be empty.";
+        }
+      ];
+    };
 }