[PATCH 5 of 5 topic-experiment] topics: abort if user wants to show the stack of a non-existent topic

[Pulkit Goyal]

# HG changeset patch
# User Pulkit Goyal <7895pulkit at gmail.com>
# Date 1497822215 -19800
#      Mon Jun 19 03:13:35 2017 +0530
# Node ID 8d8ac3adc1f9e03625d293ae78f250b115154d94
# Parent  83df91589000c05359805c96fa84a3995896ee3c
topics: abort if user wants to show the stack of a non-existent topic

diff --git a/hgext3rd/topic/stack.py b/hgext3rd/topic/stack.py
--- a/hgext3rd/topic/stack.py
+++ b/hgext3rd/topic/stack.py
@@ -22,6 +22,10 @@
     return ' '.join(prefix % suffix for suffix in labelssuffix)
 
 def showstack(ui, repo, topic, opts):
+
+    if topic not in repo.topics:
+        raise error.Abort(_('cannot resolve "%s": no such topic found') % topic)
+
     fm = ui.formatter('topicstack', opts)
     prev = None
     entries = []
diff --git a/tests/test-topic-stack.t b/tests/test-topic-stack.t
--- a/tests/test-topic-stack.t
+++ b/tests/test-topic-stack.t
@@ -319,3 +319,11 @@
   t2@ c_D (current)
   t1: c_c
     ^ c_b
+
+Trying to list non existing topic
+  $ hg stack thisdoesnotexist
+  abort: cannot resolve "thisdoesnotexist": no such topic found
+  [255]
+  $ hg topic --list thisdoesnotexist
+  abort: cannot resolve "thisdoesnotexist": no such topic found
+  [255]