fix: allow empty task list in graph builder

Signed-off-by: Jean-Baptiste Bianchi <jb.bianchi@neuroglia.io>

Author: JBBianchi

src/lib/graph-builder.ts

@@ -209,7 +209,12 @@ function getNextTask(
   taskName: string | undefined = undefined,
   transition: string | undefined = undefined,
 ): TransitionInfo {
-  if (!tasksList?.size) throw new Error('The task list cannot be empty. No tasks list to get the next task from.');
+  if (!tasksList?.size) {
+    return {
+      name: FlowDirective.Exit,
+      index: -1,
+    };
+  }
   const currentTask: Task | undefined = tasksList.get(taskName || '');
   transition = transition || currentTask?.then || '';
   if (transition == FlowDirective.End || transition == FlowDirective.Exit) {

tests/graph/graph.spec.ts

@@ -136,4 +136,11 @@ do:
     expect(forSubgraph.nodes.length).toBe(3); // entry --> waitForCheckup --> exit
     expect(forSubgraph.edges.length).toBe(2);
   });
+
+  it('should build an empty graph', () => {
+    const graph = buildGraph({} as Specification.Workflow);
+    expect(graph).toBeDefined();
+    expect(graph.nodes.length).toBe(2); // start --> end
+    expect(graph.edges.length).toBe(1);
+  });
 });