Add test for trailing whitespace

buildbot/master.sls

@@ -60,5 +60,5 @@ remove-old-build-logs:
   cron.present:
     - name: 'find /home/servo/buildbot/master/*/*.bz2 -mtime +5 -delete'
     - user: root
-    - minute: 1 
+    - minute: 1
     - hour: 0

tests/trailing_whitespace.py

@@ -0,0 +1,42 @@
+import itertools
+import re
+
+from .util import colon, color, display_path, paths, Failure, Success
+
+
+def display_trailing_whitespace(whitespace):
+    # Show trailing whitespace with printing characters and in red
+    # To make it easy to see what needs to be removed
+    replaced = whitespace.replace(' ', '-').replace('\t', r'\t')
+    return color(31, replaced)
+
+
+def display_failure(failure):
+    path, line_number, match = failure
+    line = match.group(1) + display_trailing_whitespace(match.group(2))
+    return display_path(path) + colon() + str(line_number) + colon() + line
+
+
+def check_whitespace(path):
+    CHECK_REGEX = re.compile(r'(.*?)(\s+)$')
+    trailing_whitespace = []
+    with open(path, 'r', encoding='utf-8') as file_to_check:
+        try:
+            for line_number, line in enumerate(file_to_check):
+                line = line.rstrip('\r\n')
+                match = CHECK_REGEX.match(line)
+                if match is not None:
+                    trailing_whitespace.append((path, line_number, match))
+        except UnicodeDecodeError:
+            pass  # Not a text (UTF-8) file
+    return trailing_whitespace
+
+
+def run():
+    failures = list(itertools.chain(*map(check_whitespace, paths())))
+
+    if len(failures) == 0:
+        return Success("No trailing whitespace found")
+    else:
+        output = '\n'.join([display_failure(failure) for failure in failures])
+        return Failure("Trailing whitespace found on files and lines:", output)