Fail fast if our python dependencies aren't installed – closes #236

ensime_shared/client.py

@@ -11,12 +11,14 @@
 from subprocess import PIPE, Popen
 from threading import Thread
 
+import websocket
+
 from .config import feedback, gconfig, LOG_FORMAT
 from .debugger import DebuggerClient
 from .errors import InvalidJavaPathError
 from .protocol import ProtocolHandler, ProtocolHandlerV1, ProtocolHandlerV2
 from .typecheck import TypecheckHandler
-from .util import catch, module_exists, Pretty, Util
+from .util import catch, Pretty, Util
 
 # Queue depends on python version
 if sys.version_info > (3, 0):
@@ -121,12 +123,6 @@ def setup_logger():
         thread.daemon = True
         thread.start()
 
-        self.websocket_exists = module_exists("websocket")
-        if not self.websocket_exists:
-            self.tell_module_missing("websocket-client")
-        if not module_exists("sexpdata"):
-            self.tell_module_missing("sexpdata")
-
     def queue_poll(self, sleep_t=0.5):
         """Put new messages on the queue as they arrive. Blocking in a thread.
 
@@ -148,9 +144,7 @@ def logger_and_close(msg):
                             self.teardown()
                             self._display_ws_warning()
 
-                # WebSocket exception may happen
-                # FIXME: What Exception class? Don't catch Exception
-                with catch(Exception, logger_and_close):
+                with catch(websocket.WebSocketException, logger_and_close):
                     result = self.ws.recv()
                     self.queue.put(result)
 
@@ -182,20 +176,13 @@ def lazy_initialize_ensime():
             return bool(self.ensime)
 
         def ready_to_connect():
-            if not self.websocket_exists:
-                return False
             if not self.ws and self.ensime.is_ready():
                 self.connect_ensime_server()
             return True
 
         # True if ensime is up and connection is ok, otherwise False
         return self.running and lazy_initialize_ensime() and ready_to_connect()
 
-    def tell_module_missing(self, name):
-        """Warn users that a module is not available in their machines."""
-        msg = feedback["module_missing"]
-        self.editor.raw_message(msg.format(name, name))
-
     def _display_ws_warning(self):
         warning = "A WS exception happened, 'ensime-vim' has been disabled. " +\
             "For more information, have a look at the logs in `.ensime_cache`"
@@ -211,7 +198,7 @@ def reconnect(e):
 
         self.log.debug('send: in')
         if self.running and self.ws:
-            with catch(Exception, reconnect):  # FIXME: what Exception??
+            with catch(websocket.WebSocketException, reconnect):
                 self.log.debug('send: sending JSON on WebSocket')
                 self.ws.send(msg + "\n")
 
@@ -232,14 +219,13 @@ def disable_completely(e):
                 port = self.ensime.http_port()
                 uri = "websocket" if server_v2 else "jerky"
                 self.ensime_server = gconfig["ensime_server"].format(port, uri)
-            with catch(Exception, disable_completely):
-                from websocket import create_connection
+            with catch(websocket.WebSocketException, disable_completely):
                 # Use the default timeout (no timeout).
                 options = {"subprotocols": ["jerky"]} if server_v2 else {}
                 options['enable_multithread'] = True
                 self.log.debug("About to connect to %s with options %s",
                                self.ensime_server, options)
-                self.ws = create_connection(self.ensime_server, **options)
+                self.ws = websocket.create_connection(self.ensime_server, **options)
             if self.ws:
                 self.send_request({"typehint": "ConnectionInfoReq"})
         else:

ensime_shared/config.py

@@ -29,7 +29,6 @@
     "invalid_java": "Java not found or not executable, verify :java-home in your .ensime config",
     "manual_doc": "Go to {}",
     "missing_debug_class": "You must specify a class to debug",
-    "module_missing": "{} missing: do a `pip install {}` and restart vim",
     "notify_break": "Execution paused at breakpoint line {} in {}",
     "package_inspect_current": "Using currently focused package...",
     "prompt_server_install":

ensime_shared/util.py

@@ -51,14 +51,6 @@ def catch(exception, handler=lambda e: None):
         handler(str(e))
 
 
-def module_exists(module_name):
-    res = False
-    with catch(ImportError):
-        __import__(module_name)
-        res = True
-    return res
-
-
 class Pretty(object):
     """Wrapper to pretty-format object's string representation.
 

plugin/ensime.vim

@@ -1,22 +1,48 @@
 if exists('g:loaded_ensime') || &cp
     finish
-else
-    if !has('python')
-        echohl WarningMsg
-        echomsg '[ensime] Your Vim build is missing +python support, ensime-vim will not be loaded.'
-        if has('nvim')
-            echomsg '[ensime] Did you remember to `pip2 install neovim`?'
-        else
-            echomsg '[ensime] Please review the installation guide.'
-        endif
-        echohl None
-        finish
+endif
+
+function! s:Warn(msg)
+    echohl WarningMsg | echomsg '[ensime] ' . a:msg | echohl None
+endf
+
+if !has('python')
+    call s:Warn('Your Vim build is missing +python support, ensime-vim will not be loaded.')
+    if has('nvim')
+        call s:Warn('Did you remember to `pip2 install neovim`?')
+    else
+        call s:Warn('Please review the installation guide.')
     endif
+    finish
+endif
+
+" Fail fast if dependencies are missing, we can't do much useful if so.
+" We need to wrap this in a function, see :help script-here
+function! s:DependenciesValid() abort
+    python <<PY
+import vim
+try:
+    import sexpdata
+    import websocket
 
-    " Defer to the rplugin for Neovim
-    if has('nvim') | finish | endif
+    vim.vars['ensime_deps_valid'] = True
+    del sexpdata # Clean up the shared interpreter namespace
+    del websocket
+except ImportError:
+    vim.vars['ensime_deps_valid'] = False
+PY
+
+    return g:ensime_deps_valid
+endfunction
+
+if !s:DependenciesValid()
+    call s:Warn('A dependency is missing, please `pip2 install sexpdata websocket-client` and restart Vim.')
+    finish
 endif
 
+" For Neovim, defer to the rest to the rplugin
+if has('nvim') | finish | endif
+
 augroup ensime
     autocmd!
     autocmd VimLeave *.java,*.scala call ensime#au_vim_leave(expand("<afile>"))