fix issues in Async promise execution

Author: Liang Mei

src/main/java/com/uber/cadence/internal/sync/ChildWorkflowStubImpl.java

@@ -51,6 +51,13 @@ public String getWorkflowType() {
 
   @Override
   public Promise<WorkflowExecution> getExecution() {
+    // Technically we can create and return a promise here in case the workflow is not started, and
+    // create a separate started flag for signal method to check.
+    // We don't expect this to be a critical issue for client users so we choose the simpler
+    // approach of checking and throwing exception for now.
+    if (execution == null) {
+      throw new IllegalStateException("Workflow has not started.");
+    }
     return execution;
   }
 

src/main/java/com/uber/cadence/workflow/Async.java

@@ -148,7 +148,7 @@ public static Promise<Void> procedure(Functions.Proc procedure) {
    * @return Promise that contains procedure result or failure
    */
   public static <A1> Promise<Void> procedure(Functions.Proc1<A1> procedure, A1 arg1) {
-    return procedure(() -> procedure.apply(arg1));
+    return AsyncInternal.procedure(procedure, arg1);
   }
 
   /**

src/main/java/com/uber/cadence/workflow/Functions.java

@@ -57,7 +57,7 @@ public interface Func6<T1, T2, T3, T4, T5, T6, R> extends Serializable {
   }
 
   @FunctionalInterface
-  public interface Proc {
+  public interface Proc extends Serializable {
     void apply();
   }