Restore incremental output.

dart/tools/build.py

 #!/usr/bin/env python
 #
 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 #
 
 import optparse
 import os
 import shutil
@@ skipping 255 matching lines @@
     term = os.getenv('TERM', 'dumb')
     # The capability "clr_eol" means clear the line from cursor to end
     # of line.  See man pages for tput and terminfo.
     try:
       clr_eol = subprocess.check_output(['tput', '-T' + term, 'el'],
                                         stderr=subprocess.STDOUT)
       if clr_eol:
         is_fancy_tty = True
     except subprocess.CalledProcessError:
       is_fancy_tty = False
+  has_interesting_info = False
   for line in unbuffered(process.stdout.readline):
     line = line.rstrip()
     if line.startswith('=== BUILD ') or line.startswith('** BUILD '):
-      if not is_empty_chunk(chunk):
-        print '\n'.join(chunk)
+      has_interesting_info = False
       section = line
       if is_fancy_tty:
         # If stdout is a terminal, emit "progress" information.  The
         # progress information is the first line of the current chunk.
         # After printing the line, move the cursor back to the
         # beginning of the line.  This has two effects: First, if the
         # chunk isn't empty, the first line will be overwritten
         # (avoiding duplication).  Second, the next segment line will
         # overwrite it too avoid long scrollback.  clr_eol ensures
         # that there is no trailing garbage when a shorter line
         # overwrites a longer line.
         print '%s%s\r' % (clr_eol, section),
       chunk = []
-    if not section:
+    if not section or has_interesting_info:
       print line
     else:
-      chunk.append(line)
+      length = len(chunk)
+      if length == 1 and line != 'Check dependencies':
+        has_interesting_info = True
+      elif (length == 2 or length == 3) and line:
+        has_interesting_info = True
+      if has_interesting_info:
+        print '\n'.join(chunk)
+        chunk = []
+      else:
+        chunk.append(line)
   if not is_empty_chunk(chunk):
     print '\n'.join(chunk)
 
 
 def Main():
   utils.ConfigureJava()
   # Parse the options.
   parser = BuildOptions()
   (options, args) = parser.parse_args()
   if not ProcessOptions(options, args):
@@ skipping 98 matching lines @@
         process.wait()
         if process.returncode != 0:
           print "BUILD FAILED"
           return 1
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(Main())