Add support for opening MD files directly in md_browser.

tools/md_browser/md_browser.py

 #!/usr/bin/env python
 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Simple Markdown browser for a Git checkout."""
 from __future__ import print_function
 
 import SimpleHTTPServer
 import SocketServer
 import argparse
 import codecs
 import os
 import re
 import socket
 import sys
+import threading
+import time
+import webbrowser
 
 
 THIS_DIR = os.path.abspath(os.path.dirname(__file__))
 SRC_DIR = os.path.dirname(os.path.dirname(THIS_DIR))
 sys.path.append(os.path.join(SRC_DIR, 'third_party', 'Python-Markdown'))
 import markdown
 
 
 def main(argv):
   parser = argparse.ArgumentParser(prog='md_browser')
   parser.add_argument('-p', '--port', type=int, default=8080,
                       help='port to run on (default = %(default)s)')
   parser.add_argument('-d', '--directory', type=str, default=SRC_DIR)
+  parser.add_argument('file', nargs='?',
+                      help='open file in browser')
   args = parser.parse_args(argv)
 
+  top_level = os.path.abspath(args.directory)
+
+  s = Server(args.port, top_level)
+
+  print('Listening on http://localhost:%s/' % args.port)
+  thread = None
+  if args.file:
+    path = os.path.abspath(args.file)
+    if not path.startswith(top_level):
+      print('%s is not under %s' % (args.file, args.directory))
+      return 1
+    rpath = os.path.relpath(path, top_level)
+    url = 'http://localhost:%d/%s' % (args.port, rpath)
+    print('Opening %s' % url)
+    thread = threading.Thread(target=_open_url, args=(url,))
+    thread.start()
+
+  elif os.path.isfile(os.path.join(top_level, 'docs', 'README.md')):
+    print(' Try loading http://localhost:%d/docs/README.md' % args.port)
+  elif os.path.isfile(os.path.join(args.directory, 'README.md')):
+    print(' Try loading http://localhost:%d/README.md' % args.port)
+
+  retcode = 1
   try:
-    s = Server(args.port, args.directory)
-    print("Listening on http://localhost:%s/" % args.port)
-    if os.path.isfile(os.path.join(args.directory, 'docs', 'README.md')):
-      print(" Try loading http://localhost:%s/docs/README.md" % args.port)
-    elif os.path.isfile(os.path.join(args.directory, 'README.md')):
-      print(" Try loading http://localhost:%s/README.md" % args.port)
     s.serve_forever()
-    s.shutdown()
-    return 0
   except KeyboardInterrupt:
-    return 130
+    retcode = 130
+  except Exception as e:
+    print('Exception raised: %s' % str(e))
+
+  s.shutdown()
+  if thread:
+    thread.join()
+  return retcode
+
+
+def _open_url(url):
+  time.sleep(1)
+  webbrowser.open(url)
 
 
 def _gitiles_slugify(value, _separator):
   """Convert a string (representing a section title) to URL anchor name.
 
   This function is passed to "toc" extension as an extension option, so we
   can emulate the way how Gitiles converts header titles to URL anchors.
 
   Gitiles' official documentation about the conversion is at:
 
@@ skipping 16 matching lines @@
   value = value.replace(u' ', u'-')
   value = re.sub(r'([-_])[-_]+', r'\1', value)  # Fold hyphens and underscores.
   return value
 
 
 class Server(SocketServer.TCPServer):
   def __init__(self, port, top_level):
     SocketServer.TCPServer.__init__(self, ('0.0.0.0', port), Handler)
     self.port = port
     self.top_level = os.path.abspath(top_level)
+    self.retcode = None
 
   def server_bind(self):
     self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
     self.socket.bind(self.server_address)
 
 
 class Handler(SimpleHTTPServer.SimpleHTTPRequestHandler):
   def do_GET(self):
     path = self.path
 
@@ skipping 71 matching lines @@
     self.end_headers()
 
   def _WriteTemplate(self, template):
     contents = self._Read(os.path.join('tools', 'md_browser', template),
                           relative_to=SRC_DIR)
     self.wfile.write(contents.encode('utf-8'))
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))