Add '--tail' option

Author: ruslo

bin/build.py

@@ -150,6 +150,12 @@ def PositiveInt(string):
         ' (note that full log is still available in log.txt)'
 )
 
+parser.add_argument(
+    '--tail',
+    type=PositiveInt,
+    help='Print last N lines if build failed'
+)
+
 args = parser.parse_args()
 
 polly_toolchain = detail.toolchain_name.get(args.toolchain)
@@ -247,7 +253,9 @@ def PositiveInt(string):
 polly_temp_dir = os.path.join(build_dir, '_3rdParty', 'polly')
 if not os.path.exists(polly_temp_dir):
   os.makedirs(polly_temp_dir)
-logging = detail.logging.Logging(polly_temp_dir, args.verbose, args.discard)
+logging = detail.logging.Logging(
+    polly_temp_dir, args.verbose, args.discard, args.tail
+)
 
 if os.name == 'nt':
   # Windows

bin/detail/call.py

@@ -79,7 +79,9 @@ def call(call_args, logging, cache_file='', ignore=False):
     return
   if os.path.exists(cache_file):
     os.unlink(cache_file)
+  logging.log_file.close()
   print('Command exit with status "{}": {}'.format(x, oneline))
   print('Log: {}'.format(logging.log_path))
+  logging.print_last_lines()
   print('*** FAILED ***')
   sys.exit(1)

bin/detail/logging.py

@@ -4,8 +4,20 @@
 import os
 
 class Logging:
-  def __init__(self, polly_temp_dir, verbose, discard):
+  def __init__(self, polly_temp_dir, verbose, discard, tail_N):
     self.verbose = verbose
     self.discard = discard
+    self.tail_N = tail_N
     self.log_path = os.path.join(polly_temp_dir, 'log.txt')
     self.log_file = open(self.log_path, 'w')
+
+  def print_last_lines(self):
+    if self.tail_N is None:
+      return
+    lines = open(self.log_path, 'r').readlines()
+    tail = lines[-self.tail_N:]
+    print('Last {} lines\n'.format(self.tail_N))
+    print('-' * 80)
+    for i in tail:
+      print('    {}'.format(i), end='')
+    print('-' * 80)