pyvenv in Python layer causes mmm-noweb (literate programming) to not work

Description :octocat:

I'm trying to use noweb to do literate programming, using mmm-noweb from mmm-mode. The mode is supposed to do syntax highlighting of both LaTeX and some other programming language (in my case Python) in different parts of the program.

The syntax highlighting doesn't work correctly when the package pyvenv is enabled in the python layer. The syntax highlighting works correctly in other languages inside noweb, like Lua.

Reproduction guide :beetle:

Add the noweb private layer. In ~/.emacs.d/private/noweb/packages.el write:

(defconst noweb-packages '(mmm-mode))

(defun noweb/post-init-mmm-mode ()
  (require 'mmm-noweb)
  (setq mmm-global-mode 'maybe)
  (setq mmm-mode-ext-classes-alist '((nil "\\.nw$" noweb)))
  (add-to-list 'auto-mode-alist '("\\.nw$" . latex-mode)))

If the markdown layer (which owns mmm-mode) isn't enabled, post-init-mmm-mode isn't run for some reason. I'm not sure if this is expected behaviour.

Create noweb file, test.nw:

% -*- mmm-noweb-code-mode: python-mode -*-
test
<<*>>=
if a < b:
return 4
@
bla bla

Restart Spacemacs and open test.nw

Observed behaviour: :eyes: :broken_heart:

There is no syntax highlighting for the Python bit image1. In addition, when the point is in the Python bit, the mode stays as LaTeX/MPS image2, compare mode with image1.

Expected behaviour: :heart: :smile:

There is proper syntax highlighting for both Python and LaTeX image1. When the point is in a LaTeX region, the major mode is LaTeX/MPS. When it is in a Python region, the mode is LaTeX/MPS[Python] image2, compare mode with image1.

You can reproduce this behaviour by commenting out pyvenv in the python-packages list in ~/.emacs.d/layers/+lang/python/packages.el.

System Info :computer:

OS: gnu/linux
Emacs: 25.2.2
Spacemacs: 0.200.13
Spacemacs branch: master (rev. 582f9aa4)
Graphic display: t
Distribution: spacemacs
Editing style: vim
Completion: helm

Layers:

(octave lua noweb html javascript sql emacs-lisp markdown org
    (shell :variables shell-default-height 30 shell-default-position 'bottom)
    (spell-checking :variables spell-checking-enable-by-default nil)
    syntax-checking
    (c-c++ :variables c-c++-enable-clang-support t)
    (latex :variables latex-build-command "LaTeX")
    graphviz git rust shaders
    (python :variables python-test-runner 'pytest)
    version-control ibuffer)

System configuration features: XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11

syl20bnr / spacemacs