Make errors less fatal, closes #215

Instead of using 'echoerr' and essentially breaking the plugin after
that problems are now reported as warnings with 'echomsg'. They will
also only be shown once for a particular problem.

autoload/tagbar.vim

@@ -83,6 +83,11 @@ let s:last_highlight_tline = 0
 let s:debug = 0
 let s:debug_file = ''
 
+let s:warnings = {
+    \ 'type': [],
+    \ 'encoding': 0
+\ }
+
 " s:Init() {{{2
 function! s:Init(silent) abort
     if s:checked_ctags == 2 && a:silent
@@ -801,6 +806,10 @@ function! s:InitTypes() abort
     let s:known_types.yacc = type_yacc
     " }}}3
 
+    for [type, typeinfo] in items(s:known_types)
+        let typeinfo.ftype = type
+    endfor
+
     call s:LoadUserTypeDefs()
 
     for typeinfo in values(s:known_types)
@@ -828,6 +837,7 @@ function! s:LoadUserTypeDefs(...) abort
     let transformed = {}
     for [type, def] in items(defdict)
         let transformed[type] = s:TransformUserTypeDef(def)
+        let transformed[type].ftype = type
     endfor
 
     for [key, value] in items(transformed)
@@ -1093,7 +1103,7 @@ function! s:CtagsErrMsg(errmsg, infomsg, silent, ...) abort
     endif
 
     if !a:silent
-        echoerr a:errmsg
+        call s:warning(a:errmsg)
         echomsg a:infomsg
 
         if ctags_cmd == ''
@@ -2180,7 +2190,7 @@ function! s:ExecuteCtagsOnFile(fname, realfname, typeinfo) abort
         if bufwinnr("__Tagbar__") != -1 &&
          \ (!s:known_files.has(a:realfname) ||
          \ !empty(s:known_files.get(a:realfname)))
-            echoerr 'Tagbar: Could not execute ctags for ' . a:fname . '!'
+            call s:warning('Tagbar: Could not execute ctags for ' . a:realfname . '!')
             echomsg 'Executed command: "' . ctags_cmd . '"'
             if !empty(ctags_output)
                 call s:debug('Command output:')
@@ -2273,10 +2283,14 @@ function! s:ParseTagline(part1, part2, typeinfo, fileinfo) abort
         call taginfo.initFoldState()
     catch /^Vim(\a\+):E716:/ " 'Key not present in Dictionary'
         " The tag has a 'kind' that doesn't exist in the type definition
-        call s:debug('ERROR Unknown tag kind: ' . taginfo.fields.kind)
-        echoerr 'Unknown tag kind encountered: ' . taginfo.fields.kind
-              \ 'Your ctags and Tagbar configurations are out of sync!'
-              \ 'Please read '':help tagbar-extend''.'
+        call s:debug('Warning: Unknown tag kind: ' . taginfo.fields.kind)
+        if index(s:warnings.type, a:typeinfo.ftype) == -1
+            call s:warning('Unknown tag kind encountered: ' .
+                \ '"' . taginfo.fields.kind . '".' .
+                \ ' Your ctags and Tagbar configurations are out of sync!' .
+                \ ' Please read '':help tagbar-extend''.')
+            call add(s:warnings.type, a:typeinfo.ftype)
+        endif
     endtry
 
     return taginfo
@@ -3195,7 +3209,7 @@ endfunction
 " s:SetFoldLevel() {{{2
 function! s:SetFoldLevel(level, force) abort
     if a:level < 0
-        echoerr 'Foldlevel can''t be negative'
+        call s:warning('Foldlevel can''t be negative')
         return
     endif
 
@@ -3494,9 +3508,11 @@ function! s:EscapeCtagsCmd(ctags_bin, args, ...) abort
     call s:debug('Escaped ctags command: ' . ctags_cmd)
 
     if ctags_cmd == ''
-        echoerr 'Tagbar: Encoding conversion failed!'
-              \ 'Please make sure your system is set up correctly'
-              \ 'and that Vim is compiled with the "+iconv" feature.'
+        if !s:warnings.encoding
+            call s:warning('Tagbar: Ctags command encoding conversion failed!' .
+                \ ' Please read ":h g:tagbar_systemenc".')
+            let s:warnings.encoding = 1
+        endif
     endif
 
     return ctags_cmd
@@ -3879,6 +3895,13 @@ function! s:goto_markedwin(...) abort
     endfor
 endfunction
 
+" s:warning() {{{2
+function! s:warning(msg) abort
+    echohl WarningMsg
+    echomsg a:msg
+    echohl None
+endfunction
+
 " TagbarBalloonExpr() {{{2
 function! TagbarBalloonExpr() abort
     let taginfo = s:GetTagInfo(v:beval_lnum, 1)
@@ -4086,7 +4109,7 @@ function! tagbar#gettypeconfig(type) abort
     let typeinfo = get(s:known_types, a:type, {})
 
     if empty(typeinfo)
-        echoerr 'Unknown type ' . a:type . '!'
+        call s:warning('Unknown type ' . a:type . '!')
         return
     endif