From e02d725b49e852f3aa8a5a944a1b726b651ca665 Mon Sep 17 00:00:00 2001
From: Miguel Barão <miguel.barao@gmail.com>
Date: Tue, 26 Mar 2019 18:10:59 +0000
Subject: [PATCH] Check if dependencies exist as nodes.

---
 aprendizations/learnapp.py | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/aprendizations/learnapp.py b/aprendizations/learnapp.py
index c3be9b7..0a8a66f 100644
--- a/aprendizations/learnapp.py
+++ b/aprendizations/learnapp.py
@@ -40,6 +40,11 @@ async def bcrypt_hash_gen(new_pw):
 
 
 # ============================================================================
+class LearnException(Exception):
+    pass
+
+
+# ============================================================================
 # LearnApp - application logic
 # ============================================================================
 class LearnApp(object):
@@ -256,8 +261,8 @@ class LearnApp(object):
     #
     # Edges are obtained from the deps defined in the YAML file for each topic.
     # ------------------------------------------------------------------------
-    def populate_graph(self, conffile):
-        logger.info(f'Populating graph from:  {conffile}')
+    def populate_graph(self, conffile: str):
+        logger.info(f'Populating graph from:  {conffile}...')
         config = load_yaml(conffile)    # course configuration
 
         # default attributes that apply to the topics
@@ -275,7 +280,13 @@ class LearnApp(object):
 
         g.add_nodes_from(topics.keys())
         for tref, attr in topics.items():
-            g.add_edges_from((d, tref) for d in attr.get('deps', []))
+            for d in attr.get('deps', []):
+                if d not in g.nodes():
+                    logger.error(f'Topic "{tref}" depends on "{d}" but the '
+                                 f'latter does not exist')
+                    raise LearnException()
+                else:
+                    g.add_edge(d, tref)
 
             t = g.node[tref]  # get current topic node
             t['type'] = attr.get('type', 'topic')
@@ -302,7 +313,7 @@ class LearnApp(object):
     # Buils dictionary of question factories
     # ------------------------------------------------------------------------
     def make_factory(self):
-        logger.info('Building questions factory')
+        logger.info('Building questions factory...')
         factory = {}    # {'qref': QFactory()}
         g = self.deps
         for tref in g.nodes():
--
libgit2 0.21.2