types: simplify working with client's launch args

helix-dap/examples/dap-basic.rs

@@ -33,10 +33,7 @@ pub async fn main() -> Result<()> {
         program: "/tmp/godebug/main".to_owned(),
     };
 
-    println!(
+    println!("launch: {:?}", client.launch(args).await);
-        "launch: {:?}",
-        client.launch(serde_json::to_value(args)?).await
-    );
 
     println!(
         "breakpoints: {:#?}",

helix-dap/src/client.rs

@@ -372,8 +372,9 @@ impl Client {
         Ok(())
     }
 
-    pub async fn launch(&mut self, args: Value) -> Result<()> {
+    pub async fn launch(&mut self, args: impl Serialize) -> Result<()> {
-        self.request("launch".to_owned(), Some(args)).await?;
+        self.request("launch".to_owned(), to_value(args).ok())
+            .await?;
 
         match self
             .server_rx