Only indent tikz if tikz is loaded

autoload/vimtex.vim

@@ -485,8 +485,17 @@ endfunction
 
 " }}}1
 function! s:init_local_options() " {{{1
-  let b:vimtex.sources = []
+  let b:vimtex.packages = {}
+  for l:line in vimtex#parser#tex(b:vimtex.tex, {
+        \ 'detailed' : 0,
+        \ 're_stop' : '\\begin\s*{document}',
+        \})
+    if l:line =~# '\\usepackage.*{tikz}'
+      let b:vimtex.packages.tikz = 1
+    endif
+  endfor
 
+  let b:vimtex.sources = []
   for [l:file, l:lnum, l:line] in vimtex#parser#tex(b:vimtex.tex)
     let l:cand = substitute(l:file, '\M' . b:vimtex.root, '', '')
     if l:cand[0] ==# '/' | let l:cand = l:cand[1:] | endif

indent/tex.vim

@@ -138,6 +138,8 @@ let s:re_delims = vimtex#delim#get_delim_regexes()
 
 " }}}1
 function! s:indent_tikz(lnum, prev) " {{{1
+  if !has_key(b:vimtex.packages, 'tikz') | return 0 | endif
+
   let l:env_lnum = vimtex#env#is_inside('tikzpicture')
   if l:env_lnum > 0 && l:env_lnum < a:lnum
     let l:prev_starts = a:prev =~# s:tikz_commands

test/vader/indentation.vader

@@ -141,8 +141,9 @@ Given tex (Indent: tikz):
     \end{axis}
        \end{tikzpicture}
 
-Do (Indent):
-  gg=G
+Execute (Indent):
+  let b:vimtex.packages.tikz = 1
+  normal gg=G
 
 Expect tex (Verify):
   \tikz \fill[green] rectangle (0.5,0.5); Something