Encapsulate the command builder's state flag

This also gets rid of BAD_COMMAND, which was set but never checked - the function that set the flag would immediately reset the command builder

vim-engine/src/main/kotlin/com/maddyhome/idea/vim/KeyHandler.kt

@@ -17,7 +17,6 @@ import com.maddyhome.idea.vim.command.CommandFlags
 import com.maddyhome.idea.vim.command.MappingMode
 import com.maddyhome.idea.vim.command.MappingProcessor
 import com.maddyhome.idea.vim.command.OperatorArguments
-import com.maddyhome.idea.vim.common.CurrentCommandState
 import com.maddyhome.idea.vim.diagnostic.VimLogger
 import com.maddyhome.idea.vim.diagnostic.trace
 import com.maddyhome.idea.vim.diagnostic.vimLogger
@@ -197,10 +196,9 @@ class KeyHandler {
   }
 
   private fun onUnknownKey(editor: VimEditor, keyState: KeyHandlerState) {
-    logger.trace("Command builder is set to BAD")
-    keyState.commandBuilder.commandState = CurrentCommandState.BAD_COMMAND
     editor.resetOpPending()
     editor.isReplaceCharacter = false
+    // Note that this will also reset the CommandBuilder to NEW_COMMAND
     reset(keyState, editor.mode)
   }
 
@@ -328,8 +326,7 @@ class KeyHandler {
   ) : Runnable {
     override fun run() {
       val editorState = injector.vimState
-      // TODO: This seems an unexpected place to reset command builder state
-      keyState.commandBuilder.commandState = CurrentCommandState.NEW_COMMAND
+
       val register = cmd.register
       if (register != null) {
         injector.registerGroup.selectRegister(register)
@@ -357,10 +354,7 @@ class KeyHandler {
         }
       }
 
-      // TODO: Surely the command builder is always empty at this point?
-      if (keyState.commandBuilder.isEmpty) {
-        instance.reset(keyState, editorState.mode)
-      }
+      instance.reset(keyState, editorState.mode)
     }
   }
 

vim-engine/src/main/kotlin/com/maddyhome/idea/vim/command/CommandBuilder.kt

@@ -35,6 +35,7 @@ class CommandBuilder private constructor(
   constructor(rootNode: RootNode<LazyVimCommand>, initialUncommittedRawCount: Int = 0)
     : this(rootNode, mutableListOf(initialUncommittedRawCount), mutableListOf())
 
+  private var commandState: CurrentCommandState = CurrentCommandState.NEW_COMMAND
   private var selectedRegister: Char? = null
   private var action: EditorActionHandlerBase? = null
   private var argument: Argument? = null
@@ -49,9 +50,6 @@ class CommandBuilder private constructor(
       counts[counts.size - 1] = value
     }
 
-  // TODO: Encapsulate this
-  var commandState: CurrentCommandState = CurrentCommandState.NEW_COMMAND
-
   /** Provide the typed keys for `'showcmd'` */
   val keys: Iterable<KeyStroke> get() = keyList
 
@@ -204,6 +202,12 @@ class CommandBuilder private constructor(
     keyList.add(key)
   }
 
+  /**
+   * Add an action to the command
+   *
+   * This can be an action such as delete the current character - `x`, a motion like `w`, an operator like `d` or a
+   * motion that will be used as the argument of an operator - the `w` in `dw`.
+   */
   fun addAction(action: EditorActionHandlerBase) {
     logger.trace { "addAction is executed. action = $action" }
 
@@ -230,13 +234,23 @@ class CommandBuilder private constructor(
     }
   }
 
+  /**
+   * Add an argument to the command
+   *
+   * This might be a simple character argument, such as `x` in `fx`, or an ex-string argument to a search motion, like
+   * `d/foo`. If the command is an operator+motion, the motion is both an action and an argument. While it is simpler
+   * to use [addAction], it will still work if the motion action can also be wrapped in an [Argument.Motion] and passed
+   * to [addArgument].
+   */
   fun addArgument(argument: Argument) {
     logger.trace("addArgument is executed")
 
     // If the command's action is an operator, the argument will be a motion, which might be waiting for its argument.
     // If so, update the motion argument to include the given argument
     this.argument = motionArgument?.withArgument(argument) ?: argument
 
+    fallbackArgumentType = null
+
     if (!isAwaitingArgument) {
       logger.trace("Argument is simple type, or motion with own argument. No further argument required. Setting command state to READY")
       commandState = CurrentCommandState.READY
@@ -310,6 +324,11 @@ class CommandBuilder private constructor(
     return isMultikey
   }
 
+  /**
+   * Build the command with the current counts, register, actions and arguments
+   *
+   * The command builder is reset after the command is built.
+   */
   fun buildCommand(): Command {
     val rawCount = calculateCount0Snapshot()
     val command = Command(selectedRegister, rawCount, action!!, argument, action!!.type, action?.flags ?: noneOfEnum())

vim-engine/src/main/kotlin/com/maddyhome/idea/vim/common/CurrentCommandState.kt

@@ -11,5 +11,4 @@ package com.maddyhome.idea.vim.common
 enum class CurrentCommandState {
   NEW_COMMAND,
   READY,
-  BAD_COMMAND,
 }