Bug 1318044 - Issue sgr0 after printing every line; r=froydnj

The sgr0 terminal capabity defines the byte sequence needed to reset
terminal text to its default state. For reasons documented inline in
this commit, we now print this sequence after every line printed by
mach's terminal logger.

MozReview-Commit-ID: 3RukP0QXtqy

--HG--
extra : rebase_source : 5e4b7d001300ec1059b53423b310ac9fdd514c72

python/mach/mach/logging.py

@@ -93,6 +93,7 @@ class StructuredTerminalFormatter(StructuredHumanFormatter):
 
     def set_terminal(self, terminal):
         self.terminal = terminal
+        self._sgr0 = blessings.tigetstr('sgr0') if terminal and blessings else ''
 
     def format(self, record):
         f = record.msg.format(**record.params)
@@ -102,7 +103,13 @@ class StructuredTerminalFormatter(StructuredHumanFormatter):
 
         t = self.terminal.blue(format_seconds(self._time(record)))
 
-        return '%s %s' % (t, self._colorize(f))
+        # Some processes (notably Clang) don't reset terminal attributes after
+        # printing newlines. This can lead to terminal attributes getting in a
+        # wonky state. Work around this by sending the sgr0 sequence after every
+        # line to reset all attributes. For programs that rely on the next line
+        # inheriting the same attributes, this will prevent that from happening.
+        # But that's better than "corrupting" the terminal.
+        return '%s %s%s' % (t, self._colorize(f), self._sgr0)
 
     def _colorize(self, s):
         if not self.terminal: