Add warning when an input file has no scenario code blocks

2 files changed, 13 insertions, 1 deletions

diff --git a/yarn b/yarn
index d9b2b47..fdf81a0 100755
--- a/yarn
+++ b/yarn
@@ -68,7 +68,9 @@ class YarnRunner(cliapp.Application):
     def parse_scenarios(self, filenames):
         mdparser = yarnlib.MarkdownParser()
         for filename in filenames:
-            mdparser.parse_file(filename)
+            blocks = mdparser.parse_file(filename)
+            if not blocks:
+                logging.warning('No scenario code blocks in %s' % filename)
 
         block_parser = yarnlib.BlockParser()
         block_parser.parse_blocks(mdparser.blocks)
diff --git a/yarn.tests/warn-if-empty.script b/yarn.tests/warn-if-empty.script
new file mode 100755
index 0000000..7a5c028
--- /dev/null
+++ b/yarn.tests/warn-if-empty.script
@@ -0,0 +1,10 @@
+#!/bin/sh
+
+set -eu
+
+touch "$DATADIR/empty.yarn"
+
+# The grep below will fail unless the string exists, thereby failing the
+# entire test.
+./yarn --log=/dev/stdout "$DATADIR/empty.yarn" |
+    grep 'No scenario code blocks' > /dev/null