fix: have frontend populate "stop" field in OpenAI request (#4782)

lib/llm/src/protocols/openai/completions.rs

@@ -238,7 +238,11 @@ impl OpenAIStopConditionsProvider for NvCreateCompletionRequest {
     }
 
     fn get_stop(&self) -> Option<Vec<String>> {
-        None
+        use dynamo_async_openai::types::Stop;
+        self.inner.stop.as_ref().map(|s| match s {
+            Stop::String(s) => vec![s.clone()],
+            Stop::StringArray(arr) => arr.clone(),
+        })
     }
 
     fn nvext(&self) -> Option<&NvExt> {
@@ -494,4 +498,36 @@ mod tests {
             assert_eq!(output_options.skip_special_tokens, Some(skip_value));
         }
     }
+
+    #[test]
+    fn test_stop() {
+        let null_stop = json!({
+            "model": "test-model",
+            "prompt": "Hello, world!"
+        });
+        let request: NvCreateCompletionRequest =
+            serde_json::from_value(null_stop).expect("Failed to deserialize request");
+        assert_eq!(request.get_stop(), None);
+
+        let one_stop = json!({
+            "model": "test-model",
+            "prompt": "Hello, world!",
+            "stop": "foo"
+        });
+        let request: NvCreateCompletionRequest =
+            serde_json::from_value(one_stop).expect("Failed to deserialize request");
+        assert_eq!(request.get_stop(), Some(vec!["foo".to_string()]));
+
+        let many_stops = json!({
+            "model": "test-model",
+            "prompt": "Hello, world!",
+            "stop": ["foo", "bar"]
+        });
+        let request: NvCreateCompletionRequest =
+            serde_json::from_value(many_stops).expect("Failed to deserialize request");
+        assert_eq!(
+            request.get_stop(),
+            Some(vec!["foo".to_string(), "bar".to_string()])
+        );
+    }
 }