Error when running commands without a runner pane

Previous behavior was to implicitly open a runner pane if none
attached. I regularly ran into this in unwanted circumstances. With the
recent updated to make AttachToPane smarter, an error plus quick
manual attach is nearly as quick as the implicit form, but is much
better overall.

Closes #36 - Explicitly error when running without a pane attached

plugin/vim-tmux-runner.vim

@@ -35,9 +35,7 @@ function! s:CreateRunnerPane(...)
 endfunction
 
 function! s:DetachRunnerPane()
-    if !s:RequireRunnerPane()
+    if !s:RequireRunnerPane() | return | endif
-        return
-    endif
     call s:BreakRunnerPaneToTempWindow()
     let cmd = join(["rename-window -t", s:detached_window, g:VtrDetachedName])
     call s:SendTmuxCommand(cmd)
@@ -84,9 +82,7 @@ function! s:KillDetachedWindow()
 endfunction
 
 function! s:KillRunnerPane()
-    if !s:RequireLocalPaneOrDetached()
+    if !s:RequireLocalPaneOrDetached() | return | endif
-        return
-    endif
     if exists("s:runner_pane")
         call s:KillLocalRunner()
     else
@@ -120,13 +116,13 @@ function! s:RunnerPaneDimensions()
 endfunction
 
 function! s:FocusRunnerPane()
-    call s:EnsureRunnerPane()
+    if !s:RequireRunnerPane() | return | endif
     call s:FocusTmuxPane(s:runner_pane)
     call s:SendTmuxCommand("resize-pane -Z")
 endfunction
 
 function! s:ZoomRunnerPane()
-  call s:EnsureRunnerPane()
+    if !s:RequireRunnerPane() | return | endif
     let copy_mode_cmd = s:TargetedTmuxCommand("copy-mode", s:runner_pane)
     let zoom_command = s:TargetedTmuxCommand("resize-pane -Z", s:runner_pane)
     call s:SendTmuxCommand(copy_mode_cmd)
@@ -163,9 +159,7 @@ function! s:SendEnterSequence()
 endfunction
 
 function! s:SendClearSequence()
-    if !s:RequireRunnerPane()
+    if !s:RequireRunnerPane() | return | endif
-        return
-    endif
     call s:_SendKeys(g:VtrClearSequence)
 endfunction
 
@@ -282,9 +276,7 @@ function! s:ValidRunnerPaneNumber(desired_pane)
 endfunction
 
 function! s:ReattachPane()
-    if !s:RequireDetachedPane()
+    if !s:RequireDetachedPane() | return | endif
-        return
-    endif
     call s:_ReattachPane()
     call s:FocusVimPane()
     if g:VtrClearOnReattach
@@ -293,9 +285,7 @@ function! s:ReattachPane()
 endfunction
 
 function! s:ReorientRunner()
-    if !s:RequireRunnerPane()
+    if !s:RequireRunnerPane() | return | endif
-        return
-    endif
     let temp_window = s:BreakRunnerPaneToTempWindow()
     call s:ToggleOrientationVariable()
     call s:_ReattachPane()
@@ -317,6 +307,7 @@ function! s:FlushCommand()
 endfunction
 
 function! s:SendCommandToRunner(...)
+    if !s:RequireRunnerPane() | return | endif
     if exists("a:1") && a:1 != ""
         let s:user_command = shellescape(a:1)
     endif
@@ -329,7 +320,6 @@ function! s:SendCommandToRunner(...)
         call s:EchoError("VTR: command string required")
         return
     endif
-    call s:EnsureRunnerPane()
     if g:VtrClearBeforeSend
         call s:SendClearSequence()
     endif
@@ -369,7 +359,7 @@ function! s:PrepareLines(lines)
 endfunction
 
 function! s:SendTextToRunner(lines)
-    call s:EnsureRunnerPane()
+    if !s:RequireRunnerPane() | return | endif
     let prepared = s:PrepareLines(a:lines)
     let joined_lines = join(prepared, "\r") . "\r"
     let send_keys_cmd = s:TargetedTmuxCommand("send-keys", s:runner_pane)
@@ -378,6 +368,7 @@ function! s:SendTextToRunner(lines)
 endfunction
 
 function! s:SendCtrlD()
+  if !s:RequireRunnerPane() | return | endif
   call s:SendKeys('')
 endfunction