more accurately resolve the workspace folder in handleConfigOption

These changes may matter when there are none or multiple workspace
folders.

Author: Techatrix

src/zigDiagnosticsProvider.ts

@@ -160,7 +160,7 @@ export default class ZigDiagnosticsProvider {
                 if (!buildFilePath) break;
                 processArg.push("--build-file");
                 try {
-                    processArg.push(path.resolve(handleConfigOption(buildFilePath)));
+                    processArg.push(path.resolve(handleConfigOption(buildFilePath, workspaceFolder)));
                 } catch {
                     //
                 }

src/zigUtil.ts

@@ -14,14 +14,20 @@ import which from "which";
  * Replace any references to predefined variables in config string.
  * https://code.visualstudio.com/docs/editor/variables-reference#_predefined-variables
  */
-export function handleConfigOption(input: string): string {
+export function handleConfigOption(input: string, workspaceFolder: vscode.WorkspaceFolder | "none" | "guess"): string {
     if (input.includes("${userHome}")) {
         input = input.replaceAll("${userHome}", os.homedir());
     }
 
-    if (vscode.workspace.workspaceFolders && vscode.workspace.workspaceFolders.length > 0) {
-        input = input.replaceAll("${workspaceFolder}", vscode.workspace.workspaceFolders[0].uri.fsPath);
-        input = input.replaceAll("${workspaceFolderBasename}", vscode.workspace.workspaceFolders[0].name);
+    if (workspaceFolder === "guess") {
+        workspaceFolder = vscode.workspace.workspaceFolders?.length ? vscode.workspace.workspaceFolders[0] : "none";
+    }
+
+    if (workspaceFolder !== "none") {
+        input = input.replaceAll("${workspaceFolder}", workspaceFolder.uri.fsPath);
+        input = input.replaceAll("${workspaceFolderBasename}", workspaceFolder.name);
+    } else {
+        // This may end up reporting a confusing error message.
     }
 
     const document = vscode.window.activeTextEditor?.document;
@@ -68,7 +74,7 @@ export function resolveExePathAndVersion(
     assert(cmd.length);
 
     // allow passing predefined variables
-    cmd = handleConfigOption(cmd);
+    cmd = handleConfigOption(cmd, "guess");
 
     if (cmd.startsWith("~")) {
         cmd = path.join(os.homedir(), cmd.substring(1));

src/zls.ts

@@ -170,6 +170,7 @@ function configurationMiddleware(params: ConfigurationParams): LSPAny[] | Respon
 
         const scopeUri = param.scopeUri ? client?.protocol2CodeConverter.asUri(param.scopeUri) : undefined;
         const configuration = vscode.workspace.getConfiguration("zig", scopeUri);
+        const workspaceFolder = scopeUri ? vscode.workspace.getWorkspaceFolder(scopeUri) : undefined;
 
         const updateConfigOption = (section: string, value: unknown) => {
             if (section === "zls.zigExePath") {
@@ -178,7 +179,7 @@ function configurationMiddleware(params: ConfigurationParams): LSPAny[] | Respon
 
             if (typeof value === "string") {
                 // Make sure that `""` gets converted to `undefined` and resolve predefined values
-                value = value ? handleConfigOption(value) : undefined;
+                value = value ? handleConfigOption(value, workspaceFolder ?? "guess") : undefined;
             } else if (typeof value === "object" && value !== null && !Array.isArray(value)) {
                 // Recursively update the config options
                 const newValue: Record<string, unknown> = {};