allow wait_for_predicate to return result

Do this in order to easily get results during testing

Author: mplsgrant

test/ln_test.py

@@ -2,6 +2,7 @@
 import ast
 import json
 import os
+from functools import partial
 from pathlib import Path
 from typing import Optional
 
@@ -42,10 +43,22 @@ def setup_network(self):
     def test_channel_policies(self):
         self.log.info("Ensuring node-level channel policy settings")
         graphs = []
+
+        def ln_node_has_n_edges(
+            ln: str,
+            n: int,
+        ) -> Optional[str]:
+            res = self.warnet(f"ln rpc {ln} describegraph")
+            edges = json.loads(res)["edges"]
+            if len(edges) != n:
+                return None
+            return edges
+
         for n in range(10):
             ln = f"tank-{n:04d}-ln"
-            res = self.warnet(f"ln rpc {ln} describegraph")
-            graphs.append(json.loads(res)["edges"])
+            partial_fn = partial(ln_node_has_n_edges, ln, 13)
+            edges = self.wait_for_predicate(partial_fn)
+            graphs.append(edges)
 
         def check_policy(node: int, index: int, field: str, values: tuple):
             self.log.info(f"Checking policy: Node={node} ch={index} Expected={field}:{values}")

test/test_base.py

@@ -83,8 +83,9 @@ def wait_for_predicate(self, predicate, timeout=5 * 60, interval=5):
         self.log.debug(f"Waiting for predicate with timeout {timeout}s and interval {interval}s")
         while timeout > 0:
             try:
-                if predicate():
-                    return
+                result = predicate()
+                if result:
+                    return result
             except Exception:
                 pass
             sleep(interval)