Use a prompt buffer for adding watches

This very new feature makes it kind of nice to add new watches in the
place where they will appear, keeping the eye in the same screen
location.

python3/vimspector/stack_trace.py

@@ -48,7 +48,7 @@ class StackTraceView( object ):
     self._currentThread = None
     self._threads = []
     with utils.ModifiableScratchBuffer( self._buf ):
-      self._buf[:] = None
+      utils.ClearBuffer( self._buf )
 
   def ConnectionClosed( self ):
     self.Clear()
@@ -88,7 +88,7 @@ class StackTraceView( object ):
     self._line_to_thread.clear()
 
     with utils.ModifiableScratchBuffer( self._buf ):
-      self._buf[:] = None
+      utils.ClearBuffer( self._buf )
 
       for thread in self._threads:
         icon = '+' if '_frames' not in thread else '-'

python3/vimspector/utils.py

@@ -52,9 +52,34 @@ def SetUpHiddenBuffer( buf, name ):
   buf.options[ 'bufhidden' ] = 'hide'
   buf.name = name
 
+def SetUpPromptBuffer( buf, name, prompt, callback ):
+  # This feature is _super_ new, so only enable when available
+  if not int( vim.eval( "exists( '*prompt_setprompt' )" ) ):
+    return SetUpScratchBuffer( buf, name )
+
+  buf.options[ 'buftype' ] = 'prompt'
+  buf.options[ 'swapfile' ] = False
+  buf.options[ 'modifiable' ] = True
+  buf.options[ 'modified' ] = False
+  buf.options[ 'readonly' ] = False
+  buf.options[ 'buflisted' ] = False
+  buf.options[ 'bufhidden' ] = 'wipe'
+  buf.name = name
+
+  vim.eval( "prompt_setprompt( {0}, '{1}' )".format( buf.number,
+                                                     Escape( prompt ) ) )
+  vim.eval( "prompt_setcallback( {0}, function( '{1}' ) )".format(
+    buf.number,
+    Escape( callback ) ) )
+
+
 
 @contextlib.contextmanager
 def ModifiableScratchBuffer( buf ):
+  if buf.options[ 'modifiable' ]:
+    yield
+    return
+
   buf.options[ 'modifiable' ] = True
   buf.options[ 'readonly' ] = False
   try:
@@ -189,3 +214,7 @@ def AppendToBuffer( buf, line_or_lines ):
 
   # Return the first Vim line number (1-based) that we just set.
   return line
+
+
+def ClearBuffer( buf ):
+  buf[:] = None

python3/vimspector/variables.py

@@ -60,7 +60,10 @@ class VariablesView( object ):
       'nnoremap <buffer> <DEL> :call vimspector#DeleteWatch()<CR>' )
 
     utils.SetUpScratchBuffer( self._vars.win.buffer, 'vimspector.Variables' )
-    utils.SetUpScratchBuffer( self._watch.win.buffer, 'vimspector.Watches' )
+    utils.SetUpPromptBuffer( self._watch.win.buffer,
+                             'vimspector.Watches',
+                             'Watch: ',
+                             'vimspector#AddWatchPrompt' )
 
     has_balloon      = int( vim.eval( "has( 'balloon_eval' )" ) )
     has_balloon_term = int( vim.eval( "has( 'balloon_eval_term' )" ) )
@@ -85,9 +88,9 @@ class VariablesView( object ):
 
   def Clear( self ):
     with utils.ModifiableScratchBuffer( self._vars.win.buffer ):
-      self._vars.win.buffer[:] = None
+      utils.ClearBuffer( self._vars.win.buffer )
     with utils.ModifiableScratchBuffer( self._watch.win.buffer ):
-      self._watch.win.buffer[:] = None
+      utils.ClearBuffer( self._watch.win.buffer )
 
   def ConnectionClosed( self ):
     self.Clear()
@@ -251,7 +254,7 @@ class VariablesView( object ):
     self._vars.lines.clear()
     with utils.RestoreCursorPosition():
       with utils.ModifiableScratchBuffer( self._vars.win.buffer ):
-        self._vars.win.buffer[:] = None
+        utils.ClearBuffer( self._vars.win.buffer )
         for scope in self._scopes:
           self._DrawScope( 0, scope )
 
@@ -263,7 +266,7 @@ class VariablesView( object ):
     self._watch.lines.clear()
     with utils.RestoreCursorPosition():
       with utils.ModifiableScratchBuffer( self._watch.win.buffer ):
-        self._watch.win.buffer[:] = None
+        utils.ClearBuffer( self._watch.win.buffer )
         utils.AppendToBuffer( self._watch.win.buffer, 'Watches: ----' )
         for watch in self._watches:
           line = utils.AppendToBuffer( self._watch.win.buffer,
@@ -297,8 +300,7 @@ class VariablesView( object ):
     line =  '{0}{1} Result: {2} '.format( ' ' * indent,
                                           icon,
                                           result[ 'result' ] )
-    line = utils.AppendToBuffer( self._watch.win.buffer,
-                                 line.split( '\n' ) )
+    line = utils.AppendToBuffer( self._watch.win.buffer, line.split( '\n' ) )
     self._watch.lines[ line ] = result
 
     if '_variables' in result: