Import requests module lazily

The requests module is slow to load so we should import it only when needed to reduce startup time.

autoload/youcompleteme.vim

@@ -82,7 +82,7 @@ function! youcompleteme#Enable()
     " Note that these events will NOT trigger for the file vim is started with;
     " so if you do "vim foo.cc", these events will not trigger when that buffer
     " is read. This is because youcompleteme#Enable() is called on VimEnter and
-    " that happens *after" BufRead/BufEnter has already triggered for the
+    " that happens *after* BufRead/FileType has already triggered for the
     " initial file.
     " We also need to trigger buf init code on the FileType event because when
     " the user does :enew and then :set ft=something, we need to run buf init
@@ -97,10 +97,15 @@ function! youcompleteme#Enable()
     autocmd CompleteDone * call s:OnCompleteDone()
   augroup END
 
-  " Calling this once solves the problem of BufRead/BufEnter not triggering for
-  " the first loaded file. This should be the last command executed in this
-  " function!
-  call s:OnBufferRead()
+  " BufRead/FileType events are not triggered for the first loaded file.
+  " However, we don't directly call the s:OnBufferRead function because it would
+  " send requests that can't succeed as the server is not ready yet and would
+  " slow down startup.
+  call s:DisableOnLargeFile( expand( '%' ) )
+
+  if s:AllowedToCompleteInCurrentBuffer()
+    call s:SetCompleteFunc()
+  endif
 endfunction
 
 

python/ycm/client/base_request.py

@@ -25,20 +25,16 @@ from builtins import *  # noqa
 
 import contextlib
 import logging
-import requests
 import urllib.parse
 import json
 from future.utils import native
 from base64 import b64decode, b64encode
-from requests_futures.sessions import FuturesSession
-from ycm.unsafe_thread_pool_executor import UnsafeThreadPoolExecutor
 from ycm import vimsupport
 from ycmd.utils import ToBytes
 from ycmd.hmac_utils import CreateRequestHmac, CreateHmac, SecureBytesEqual
 from ycmd.responses import ServerError, UnknownExtraConf
 
 _HEADERS = {'content-type': 'application/json'}
-_EXECUTOR = UnsafeThreadPoolExecutor( max_workers = 30 )
 _CONNECT_TIMEOUT_SEC = 0.01
 # Setting this to None seems to screw up the Requests/urllib3 libs.
 _READ_TIMEOUT_SEC = 30
@@ -104,14 +100,14 @@ class BaseRequest( object ):
     request_uri = _BuildUri( handler )
     if method == 'POST':
       sent_data = _ToUtf8Json( data )
-      return BaseRequest.session.post(
+      return BaseRequest.Session().post(
           request_uri,
           data = sent_data,
           headers = BaseRequest._ExtraHeaders( method,
                                                request_uri,
                                                sent_data ),
           timeout = ( _CONNECT_TIMEOUT_SEC, timeout ) )
-    return BaseRequest.session.get(
+    return BaseRequest.Session().get(
         request_uri,
         headers = BaseRequest._ExtraHeaders( method, request_uri ),
         timeout = ( _CONNECT_TIMEOUT_SEC, timeout ) )
@@ -129,7 +125,31 @@ class BaseRequest( object ):
                            BaseRequest.hmac_secret ) )
     return headers
 
-  session = FuturesSession( executor = _EXECUTOR )
+
+  # These two methods exist to avoid importing the requests module at startup;
+  # reducing loading time since this module is slow to import.
+  @classmethod
+  def Requests( cls ):
+    try:
+      return cls.requests
+    except AttributeError:
+      import requests
+      cls.requests = requests
+      return requests
+
+
+  @classmethod
+  def Session( cls ):
+    try:
+      return cls.session
+    except AttributeError:
+      from ycm.unsafe_thread_pool_executor import UnsafeThreadPoolExecutor
+      from requests_futures.sessions import FuturesSession
+      executor = UnsafeThreadPoolExecutor( max_workers = 30 )
+      cls.session = FuturesSession( executor = executor )
+      return cls.session
+
+
   server_location = ''
   hmac_secret = ''
 
@@ -161,7 +181,7 @@ def BuildRequestData( filepath = None ):
 def JsonFromFuture( future ):
   response = future.result()
   _ValidateResponseObject( response )
-  if response.status_code == requests.codes.server_error:
+  if response.status_code == BaseRequest.Requests().codes.server_error:
     raise MakeServerException( response.json() )
 
   # We let Requests handle the other status types, we only handle the 500
@@ -199,7 +219,7 @@ def HandleServerException( display = True, truncate = False ):
         _LoadExtraConfFile( e.extra_conf_file )
       else:
         _IgnoreExtraConfFile( e.extra_conf_file )
-  except requests.exceptions.ConnectionError:
+  except BaseRequest.Requests().exceptions.ConnectionError:
     # We don't display this exception to the user since it is likely to happen
     # for each subsequent request (typically if the server crashed) and we
     # don't want to spam the user with it.