Make neovim config more composable per-language.

jrpotter/neovim/default.nix

@@ -1,33 +1,13 @@
-args @ { pkgs, ... }:
+{ config, pkgs, lib, ... }:
 let
-  conf = {
-    lua = import ./lua.nix args;
-    nix = import ./nix.nix args;
-    python = import ./python.nix args;
-  };
-
   nvim-dap = {
     plugin = pkgs.vimPlugins.nvim-dap;
-    config = ''
-      lua << EOF
-      ${builtins.concatStringsSep "\n" (builtins.map (m: "do\n${m}\nend") [
-        conf.python.nvim-dap
-      ])}
-      EOF
-    '';
+    config = config.programs.neovim.nvim-dap;
   };
 
   nvim-lspconfig = {
     plugin = pkgs.vimPlugins.nvim-lspconfig;
-    config = ''
-      lua << EOF
-      ${builtins.concatStringsSep "\n" (builtins.map (m: "do\n${m}\nend") [
-        conf.lua.nvim-lspconfig
-        conf.nix.nvim-lspconfig
-        conf.python.nvim-lspconfig
-      ])}
-      EOF
-    '';
+    config = config.programs.neovim.nvim-lspconfig;
   };
 
   nvim-treesitter = {
@@ -39,7 +19,6 @@ let
       ]
     ));
     config = ''
-      lua << EOF
       require('nvim-treesitter.configs').setup {
         auto_install = false,
         highlight = { enable = true },
@@ -53,24 +32,44 @@ let
           },
         },
       }
-      EOF
     '';
   };
 in
 {
-  programs.neovim = {
-    extraLuaConfig = ''
-      vim.o.colorcolumn = '80,100'
-      vim.o.expandtab = true  -- Spaces instead of tabs.
-      vim.o.shiftwidth = 2    -- # of spaces to use for each (auto)indent.
-      vim.o.tabstop = 2       -- # of spaces a <Tab> in the file counts for.
+  options.programs.neovim = {
+    nvim-dap = lib.mkOption {
+      type = lib.types.lines;
+      example = ''
+        require('...').nvim_dap()
       '';
-    extraPackages = (
-      conf.lua.extraPackages ++
-      conf.nix.extraPackages ++
-      conf.python.extraPackages
-    );
-    plugins = [
+      description = lib.mdDoc ''
+        Language-specific configurations for the `nvim-dap` plugin.
+      '';
+    };
+
+    nvim-lspconfig = lib.mkOption {
+      type = lib.types.lines;
+      example = ''
+        require('...').nvim_lspconfig()
+      '';
+      description = lib.mdDoc ''
+        Language-specific configurations for the `nvim-lspconfig` plugin.
+      '';
+    };
+  };
+
+  imports = [
+    ./lang/lua.nix
+    ./lang/nix.nix
+    ./lang/python.nix
+  ];
+
+  config = {
+    programs.neovim = {
+      plugins = map (p: {
+        inherit (p) plugin;
+        config = "lua << EOF\n${p.config}\nEOF";
+      }) [
         nvim-dap
         nvim-lspconfig
         nvim-treesitter
@@ -78,4 +77,29 @@ in
       viAlias = true;
       vimAlias = true;
     };
+
+    xdg.configFile."nvim/init.lua".text = lib.mkMerge [
+      # Extra Lua configuration to be prepended to `init.lua`. Extend the Lua
+      # loader to search for our /nix/store/.../?.lua files.
+      (let
+        lua = pkgs.stdenv.mkDerivation {
+          name = "lua";
+          src = ./lua;
+          installPhase = ''
+            mkdir -p $out/
+            cp -r ./* $out/
+          '';
+        };
+        in lib.mkBefore ''
+          package.path = '${lua}/?.lua;' .. package.path
+        '')
+      # Extra Lua configuration to be appended to `init.lua`.
+      (lib.mkAfter ''
+        vim.o.colorcolumn = '80,100'
+        vim.o.expandtab = true  -- Spaces instead of tabs.
+        vim.o.shiftwidth = 2    -- # of spaces to use for each (auto)indent.
+        vim.o.tabstop = 2       -- # of spaces a <Tab> in the file counts for.
+      '')
+    ];
+  };
 }

jrpotter/neovim/lang/lua.nix

@@ -0,0 +1,10 @@
+{ pkgs, ... }:
+{
+  programs.neovim = {
+    nvim-lspconfig = ''
+      require('lspconfig').lua_ls.setup { }
+    '';
+
+    extraPackages = [ pkgs.lua-language-server ];
+  };
+}

jrpotter/neovim/lang/nix.nix

@@ -0,0 +1,10 @@
+{ pkgs, ... }:
+{
+  programs.neovim = {
+    nvim-lspconfig = ''
+      require('lspconfig').nil_ls.setup {}
+    '';
+
+    extraPackages = [ pkgs.nil ];
+  };
+}

jrpotter/neovim/lang/python.nix

@@ -0,0 +1,26 @@
+{ pkgs, ... }:
+let
+  venv = pkgs.python3.withPackages (ps: with ps; [
+    debugpy
+    mccabe
+    pycodestyle
+    pyflakes
+    python-lsp-server
+    python-lsp-black
+  ]);
+in
+{
+  programs.neovim = {
+    nvim-dap = ''
+      require('init.python').nvim_dap({
+        command = '${venv}/bin/python3.10',
+      })
+    '';
+
+    nvim-lspconfig = ''
+      require('init.python').nvim_lspconfig()
+    '';
+
+    extraPackages = [ venv ];
+  };
+}

jrpotter/neovim/lua.nix

@@ -1,10 +0,0 @@
-{ pkgs, ... }:
-{
-  nvim-lspconfig = ''
-    require('lspconfig').lua_ls.setup { }
-  '';
-
-  extraPackages = with pkgs; [
-    lua-language-server
-  ];
-}

jrpotter/neovim/lua/init/python.lua

@@ -0,0 +1,49 @@
+local module = {}
+
+function module.nvim_dap(options)
+  local dap = require('dap')
+
+  dap.adapters.python = function(callback, config)
+    callback({
+      name = 'debugpy',
+      type = 'executable',
+      command = options.command,
+      args = { '-m', 'debugpy.adapter' },
+      options = {
+        source_filetype = 'python',
+      },
+    })
+  end
+
+  dap.configurations.python = dap.configurations.python or {}
+  table.insert(dap.configurations.python, {
+    name = 'Launch',
+    type = 'python',
+    request = 'launch',
+    program = '${file}',
+    cwd = '${workspaceFolder}',
+  })
+end
+
+function module.nvim_lspconfig()
+  require('lspconfig').pylsp.setup {
+    settings = {
+      pylsp = {
+        -- `flake8` currently fails in some cases. Prefer the default set of
+        -- utilities instead.
+        -- https://github.com/python-lsp/python-lsp-server/pull/434
+        configurationSources = 'pycodestyle',
+        plugins = {
+          autopep8 = { enabled = false },
+          black = { enabled = true },
+          mccabe = { enabled = true },
+          pycodestyle = { enabled = true },
+          pyflakes = { enabled = true },
+          yapf = { enabled = false },
+        },
+      },
+    },
+  }
+end
+
+return module

jrpotter/neovim/nix.nix

@@ -1,10 +0,0 @@
-{ pkgs, ... }:
-{
-  nvim-lspconfig = ''
-    require('lspconfig').nil_ls.setup { }
-  '';
-
-  extraPackages = with pkgs; [
-    nil
-  ];
-}

jrpotter/neovim/python.nix

@@ -1,61 +0,0 @@
-{ pkgs, ... }:
-let
-  venv = pkgs.python3.withPackages (ps: with ps; [
-    debugpy
-    mccabe
-    pycodestyle
-    pyflakes
-    python-lsp-server
-    python-lsp-black
-  ]);
-in
-{
-  nvim-dap = ''
-    local dap = require('dap')
-
-    dap.adapters.python = function(callback, config)
-      callback({
-        name = 'debugpy',
-        type = 'executable',
-        command = '${venv}/bin/python3.10',
-        args = { '-m', 'debugpy.adapter' },
-        options = {
-          source_filetype = 'python',
-        },
-      })
-    end
-
-    dap.configurations.python = dap.configurations.python or {}
-    table.insert(dap.configurations.python, {
-      name = 'Launch',
-      type = 'python',
-      request = 'launch',
-      program = "''${file}",
-      cwd = "''${workspaceFolder}",
-    })
-  '';
-
-  nvim-lspconfig = ''
-    require('lspconfig').pylsp.setup {
-      settings = {
-        pylsp = {
-          -- `flake8` currently fails in some cases:
-          -- https://github.com/python-lsp/python-lsp-server/pull/434
-          configurationSources = 'pycodestyle',
-          plugins = {
-            autopep8 = { enabled = false },
-            black = { enabled = true },
-            mccabe = { enabled = true },
-            pycodestyle = { enabled = true },
-            pyflakes = { enabled = true },
-            yapf = { enabled = false },
-          },
-        },
-      },
-    }
-  '';
-
-  extraPackages = [
-    venv
-  ];
-}