cros lint: detect & warn about trailing newlines

So we don't have to have reviewers catch these errors, add a linter check.

BUG=None
TEST=`cros lint` detected a few files with bad trailing newlines

Change-Id: I6dd90e25516e77902fa91227b2d4c4036cc7d11a
Reviewed-on: https://chromium-review.googlesource.com/307175
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Paul Hobbs <phobbs@google.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/cli/cros/lint.py b/cli/cros/lint.py
index f54c8a6b9..5f9547105 100644
--- a/cli/cros/lint.py
+++ b/cli/cros/lint.py
@@ -385,6 +385,7 @@ class SourceChecker(BaseChecker):
   class _MessageR9200(object): pass
   class _MessageR9201(object): pass
   class _MessageR9202(object): pass
+  class _MessageR9210(object): pass
   # pylint: enable=class-missing-docstring,multiple-statements
 
   name = 'source_checker'
@@ -397,6 +398,8 @@ class SourceChecker(BaseChecker):
                 ('missing-shebang'), _MessageR9201),
       'R9202': ('Shebang is set, but file is not executable',
                 ('spurious-shebang'), _MessageR9202),
+      'R9210': ('Trailing new lines found at end of file',
+                ('excess-trailing-newlines'), _MessageR9210),
   }
   options = ()
 
@@ -405,6 +408,7 @@ class SourceChecker(BaseChecker):
     stream = node.file_stream
     stream.seek(0)
     self._check_shebang(node, stream)
+    self._check_trailing_lines(node, stream)
 
   def _check_shebang(self, _node, stream):
     """Verify the shebang is version specific"""
@@ -424,6 +428,14 @@ class SourceChecker(BaseChecker):
     if parts[0] not in ('#!/usr/bin/python2', '#!/usr/bin/python3'):
       self.add_message('R9200')
 
+  def _check_trailing_lines(self, _node, stream):
+    """Reject trailing lines"""
+    st = os.fstat(stream.fileno())
+    if st.st_size > 1:
+      stream.seek(st.st_size - 2)
+      if not stream.read().strip('\n'):
+        self.add_message('R9210')
+
 
 class ChromiteLoggingChecker(BaseChecker):
   """Make sure we enforce rules on importing logging."""