Ensure runner_pane is valid before using

This protects all commands that expect a runner pane from runner
against an invalid pane, including the Vim pane. Since the user can
modified the tmux layout and open and close panes outside the context
of VTR, it's neccesary to check this before any command that requires
the runner pane.

Closes #28 - Protect against running command against invalid panes

plugin/vim-tmux-runner.vim

@@ -35,23 +35,27 @@ function! s:CreateRunnerPane(...)
 endfunction
 
 function! s:DetachRunnerPane()
-    if !s:RequireRunnerPane() | return | endif
+    if !s:ValidRunnerPaneSet() | return | endif
     call s:BreakRunnerPaneToTempWindow()
     let cmd = join(["rename-window -t", s:detached_window, g:VtrDetachedName])
     call s:SendTmuxCommand(cmd)
 endfunction
 
-function! s:RequireRunnerPane()
+function! s:ValidRunnerPaneSet()
     if !exists("s:runner_pane")
-        call s:EchoError("VTR: No runner pane attached.")
+        call s:EchoError("No runner pane attached.")
+        return 0
+    endif
+    if !s:ValidRunnerPaneNumber(s:runner_pane)
+        call s:EchoError("Runner pane setting (" . s:runner_pane . ") is invalid. Please reattach.")
         return 0
     endif
     return 1
 endfunction
 
-function! s:RequireDetachedPane()
+function! s:DetachedPaneAvailable()
     if !exists("s:detached_window")
-        call s:EchoError("VTR: No detached runner pane.")
+        call s:EchoError("No detached runner pane.")
         return 0
     endif
     return 1
@@ -59,7 +63,7 @@ endfunction
 
 function! s:RequireLocalPaneOrDetached()
     if !exists('s:detached_window') && !exists('s:runner_pane')
-        call s:EchoError("VTR: No pane, local or detached.")
+        call s:EchoError("No pane, local or detached.")
         return 0
     endif
     return 1
@@ -116,7 +120,7 @@ function! s:RunnerPaneDimensions()
 endfunction
 
 function! s:FocusRunnerPane()
-    if !s:RequireRunnerPane() | return | endif
+    if !s:ValidRunnerPaneSet() | return | endif
     call s:FocusTmuxPane(s:runner_pane)
     call s:SendTmuxCommand("resize-pane -Z")
 endfunction
@@ -151,7 +155,7 @@ function! s:SendEnterSequence()
 endfunction
 
 function! s:SendClearSequence()
-    if !s:RequireRunnerPane() | return | endif
+    if !s:ValidRunnerPaneSet() | return | endif
     call s:_SendKeys(g:VtrClearSequence)
 endfunction
 
@@ -219,7 +223,7 @@ function! s:AltPane()
   if s:PaneCount() == 2
     return s:AvailableRunnerPaneIndices()[0]
   else
-    echoerr "VTR: AltPane only valid if two panes open"
+    echoerr "AltPane only valid if two panes open"
   endif
 endfunction
 
@@ -258,7 +262,7 @@ function! s:AttachToPane(desired_pane)
 endfunction
 
 function! s:EchoError(message)
-  echohl ErrorMsg | echo "\r". a:message | echohl None
+  echohl ErrorMsg | echo "\rVTR: ". a:message | echohl None
 endfunction
 
 function! s:ValidRunnerPaneNumber(desired_pane)
@@ -268,7 +272,7 @@ function! s:ValidRunnerPaneNumber(desired_pane)
 endfunction
 
 function! s:ReattachPane()
-    if !s:RequireDetachedPane() | return | endif
+    if !s:DetachedPaneAvailable() | return | endif
     call s:_ReattachPane()
     call s:FocusVimPane()
     if g:VtrClearOnReattach
@@ -277,7 +281,7 @@ function! s:ReattachPane()
 endfunction
 
 function! s:ReorientRunner()
-    if !s:RequireRunnerPane() | return | endif
+    if !s:ValidRunnerPaneSet() | return | endif
     let temp_window = s:BreakRunnerPaneToTempWindow()
     call s:ToggleOrientationVariable()
     call s:_ReattachPane()
@@ -299,7 +303,7 @@ function! s:FlushCommand()
 endfunction
 
 function! s:SendCommandToRunner(...)
-    if !s:RequireRunnerPane() | return | endif
+    if !s:ValidRunnerPaneSet() | return | endif
     if exists("a:1") && a:1 != ""
         let s:user_command = shellescape(a:1)
     endif
@@ -309,7 +313,7 @@ function! s:SendCommandToRunner(...)
     let escaped_empty_string = "''"
     if s:user_command == escaped_empty_string
         unlet s:user_command
-        call s:EchoError("VTR: command string required")
+        call s:EchoError("command string required")
         return
     endif
     if g:VtrClearBeforeSend
@@ -351,7 +355,7 @@ function! s:PrepareLines(lines)
 endfunction
 
 function! s:SendTextToRunner(lines)
-    if !s:RequireRunnerPane() | return | endif
+    if !s:ValidRunnerPaneSet() | 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)
@@ -360,7 +364,7 @@ function! s:SendTextToRunner(lines)
 endfunction
 
 function! s:SendCtrlD()
-  if !s:RequireRunnerPane() | return | endif
+  if !s:ValidRunnerPaneSet() | return | endif
   call s:SendKeys('')
 endfunction