Ensure CompletionsResponse contains targets (microsoft#362)

mfussenegger · web-flow · commit f15f84bca99b · 2021-06-17T15:05:03.000+08:00
If a client sent a completion request without a frameId then the server returned a completion response without targets. According to the specification the response of a completions request must always contain a `targets` property. It is not optional. See https://microsoft.github.io/debug-adapter-protocol/specification#Requests_Completions
diff --git a/com.microsoft.java.debug.core/src/main/java/com/microsoft/java/debug/core/adapter/handler/CompletionsHandler.java b/com.microsoft.java.debug.core/src/main/java/com/microsoft/java/debug/core/adapter/handler/CompletionsHandler.java
@@ -11,8 +11,8 @@
 
 package com.microsoft.java.debug.core.adapter.handler;
 
-import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
 
@@ -46,7 +46,7 @@ public CompletableFuture<Response> handle(Command command, Arguments arguments,
         // completions should be illegal when frameId is zero, it is sent when the program is running, while during running we cannot resolve
         // the completion candidates
         if (completionsArgs.frameId == 0) {
-            response.body = new ArrayList<>();
+            response.body = new Responses.CompletionsResponseBody(Collections.emptyList());
             return CompletableFuture.completedFuture(response);
         }
 
