feat: passing settings to lsp (#294)

* feat: passing settings to lsp

allows passing settings to language servers via config.serverSettings.

* cleanup package.json

README.md

@@ -27,6 +27,23 @@ The following are tested so far:
     }
     ```
 
+  Pass settings to the language server via `serverSettings`.
+    ```jsonc
+    {
+      "nix.serverSettings": {
+        // settings for 'nil' LSP
+        "nil": {
+          "diagnostics": {
+            "ignored": ["unused_binding", "unused_with"]
+          },
+          "formatting": {
+            "command": ["nixpkgs-fmt"]
+          }
+        }
+      }
+    }
+    ```
+
 * When `Language Server` support is not enabled the following tools are used to
   + Formatting support. Set `nix.formatterPath` to any command which can accept file contents on stdin and return formatted text on stdout; e.g.,
       ```jsonc

package.json

@@ -87,6 +87,11 @@
           "type": "boolean",
           "default": false,
           "description": "Use LSP instead of nix-instantiate and nixpkgs-fmt."
+        },
+        "nix.serverSettings": {
+          "type": "object",
+          "default": {},
+          "description": "Settings passed to the language server on configuration requests."
         }
       }
     },

src/client.ts

@@ -1,7 +1,11 @@
 // from PR of https://github.com/nix-community/vscode-nix-ide/pull/16/
 
 import { env, ExtensionContext, Uri, window, workspace } from "vscode";
-import { LanguageClientOptions } from "vscode-languageclient";
+import {
+  LanguageClientOptions,
+  LSPArray,
+  ConfigurationParams,
+} from "vscode-languageclient";
 import {
   Executable,
   LanguageClient,
@@ -41,13 +45,33 @@ export async function activate(context: ExtensionContext): Promise<void> {
     documentSelector: nixDocumentSelector,
     synchronize: {
       fileEvents: workspace.createFileSystemWatcher("**/*.nix"),
+      configurationSection: [config.rootSection],
     },
     outputChannel: window.createOutputChannel("Nix"),
+    middleware: {
+      workspace: {
+        configuration: (params: ConfigurationParams): LSPArray[] => {
+          const items = params.items || [];
+          const res: LSPArray = [];
+          const settings = config.serverSettings;
+          for (const item of items) {
+            if (!item?.section) {
+              continue;
+            }
+            res.push(settings[item.section as keyof typeof settings] ?? null);
+          }
+          // eslint-disable-next-line @typescript-eslint/no-unsafe-return
+          return res;
+        },
+      },
+    },
   };
 
   client = new LanguageClient("nix", "Nix", serverOptions, clientOptions);
   client.registerProposedFeatures();
-  context.subscriptions.push(client.start());
+  await client.start();
+
+  context.subscriptions.push(client);
 }
 
 export function deactivate(): Thenable<void> | undefined {

src/configuration.ts

@@ -1,4 +1,5 @@
 import { WorkspaceConfiguration, workspace } from "vscode";
+import { LSPObject } from "vscode-languageclient";
 
 import { MessageItem, Uri } from "vscode";
 
@@ -28,5 +29,9 @@ export class Config {
   get LSPEnabled(): boolean {
     return this.get<boolean>("enableLanguageServer", false);
   }
+
+  get serverSettings(): LSPObject {
+    return this.get<LSPObject>("serverSettings", {});
+  }
 }
 export const config = new Config();