Vimtex: Nested dot2tex syntax not working in included file

[timokau]

Describe the issue

Nested dot2tex highlighting only works when the dot2tex environment is in a document environment. That is not the case when e.g. a chapter is written in a separate file an included with \input.

Steps to reproduce

```tex
%\begin{document} % works with this surrounding environment
\begin{dot2tex}[circo,tikzedgelabels,options=-t raw]
digraph G {
edge [lblstyle="above, sloped"];
b1[label="$B1$",shape="box"];
b2[label="$B2$"];
b3[label="$B3$",shape="doublecircle"];

    b1 -> b2[label="$5$"]
    b2 -> b3[label="$6$"]
}

\end{dot2tex}
%\end{document}
```

Output from VimtexInfo

System info
  OS: Linux 4.19.50
  Vim version: NVIM v0.3.7
  Has clientserver: true
  Servername: /tmp/nvim9TEfF2/0

vimtex project: minimal
  base: minimal.tex
  root: /home/timo/tmp/reprod
  tex: /home/timo/tmp/reprod/minimal.tex
  out: /home/timo/tmp/reprod/minimal.pdf
  log: /home/timo/tmp/reprod/minimal.log
  aux: /home/timo/tmp/reprod/minimal.aux
  fls: /home/timo/tmp/reprod/minimal.fls
  compiler: latexmk
    backend: nvim
    output: /tmp/nvim9TEfF2/1
    configuration: 
      continuous: 1
      callback: 1
      latexmk options:
        -verbose
        -file-line-error
        -synctex=1
        -interaction=nonstopmode
      latexmk engine: -pdf
  viewer: Zathura
    xwin id: 0
  qf: LaTeX logfile
    config: 
      ignore_filters:
        LaTeX Warning: Marginpar on page \d\+ moved.
      fix_paths: 1
      packages: 
        default: 1
      default: 1
  document class: minimal

[lervag]

I'm sorry, but you're example is not an example of the issue. Can you please update? I.e., for me, your example seems to have the correct syntax highlighting.

[timokau]

I'm sure I remember writing something of the lines of "then delete \begin{document} and it doesn't highlight anymore", but apparently I didn't. Updated.

[lervag]

Ok. For me, this actually still works in both cases. Please see the minimal example I've pushed in c7cbc9d.

[timokau]

You're right. Again, I remember seeing the issue in the example I provided, but I must've been confused. Sorry.

Its not actually due to the document environment, but due to having a preceding chapter. Here's a new example:

\chapter{test} % works without this line, same goes for (sub)section but not for arbitrary commands like emph
\begin{dot2tex}
  digraph G {
    b1 -> b2
  }
\end{dot2tex}

[lervag]

Ah, there it is. It should be fixed now.

[timokau]

Thank you!

[lervag]

No problem :)