null-ls: init with prettier and flake8 (#31)

plugins/null-ls/servers.nix

@@ -0,0 +1,33 @@
+{ pkgs, config, lib, ... }@args:
+let
+  helpers = import ./helpers.nix args;
+  serverData = {
+    code_actions = {
+    };
+    completion = {
+    };
+    diagnostics = {
+    };
+    formatting = {
+      prettier = {
+        packages = [ pkgs.nodePackages.prettier ];
+      };
+      flake8 = {
+        packages = [ pkgs.python3Packages.flake8 ];
+      };
+    };
+  };
+  # Format the servers to be an array of attrs like the following example
+  # [{
+  #   name = "prettier";
+  #   sourceType = "formatting";
+  #   packages = [...];
+  # }]
+  serverDataFormatted = lib.mapAttrsToList (sourceType: sourceSet:
+    lib.mapAttrsToList (name: attrs: attrs // { inherit sourceType name; }) sourceSet
+  ) serverData;
+  dataFlattened = lib.flatten serverDataFormatted;
+in
+{
+  imports = lib.lists.map (helpers.mkServer) dataFlattened;
+}