Syntax highlight narrowed python string literals as code

Question

I have some python code, that has some long string literals containing more python code. These strings should most of the time be uniformly colored, as happens by default.

However, I would like to be able to some times narrow my buffer to any of these strings, and then have emacs syntax highlight them as if they were code, not strings within code (i.e. as if the """ weren't there in the original buffer)

Is there any way to do that, that does not involve lots of elisp?

NOTE: I do not need to necessarily need narrowing, just seemed better to change the syntax highlighting like that, as in the full buffer it would be confusing...

Wouldn't narrowing to only the contents of the string, not including the quotes, solve the problem? — Jordon Biondo, Mar 09 '16 at 15:28
A while ago I saw someone doing something similar in HTML mode, but right now I remember where I saw it. Anyway, the basic idea was to copy the embedded code to a new buffer and display it using the proper major mode. Once done, a magic key sequence (like C-c C-c) would copy the result back where it originally case from. Unfortunately, it would require writing some elisp, I'm afraid. — Lindydancer, Mar 09 '16 at 16:06
@JordonBiondo In my, narrowing to the string (without quotes) does not change highlighting... also running `font-lock-fontify-buffer` does not help — jmlorenzi, Mar 09 '16 at 16:13
@Lindydancer Thanks! I thought something like that should be doable, but my elisp skill is really low... I hope I get some time to try and do this... — jmlorenzi, Mar 09 '16 at 16:15
@jmlorenzi after you narrow you can change the major mode to support whatever highlighting you want. Then change it back once you widen. @lindydancer is talking about the `string-edit` package, but it would not support highlighting like you want. — Jordon Biondo, Mar 09 '16 at 16:15

PythonNut · Accepted Answer · 2016-03-10T03:37:55.987

3

This can be done with polymode.

(require 'polymode)
(defcustom pm-host/python
  (pm-bchunkmode "python"
                 :mode 'python-mode
                 :font-lock-narrow nil)
  "Python host chunkmode"
  :group 'hostmodes
  :type 'object)

(defcustom pm-inner/python
  (pm-hbtchunkmode "python"
                   :mode 'python-mode
                   :head-reg  "\"\"\""
                   :tail-reg  "\"\"\"")
  "Python typical chunk."
  :group 'innermodes
  :type 'object)

(defcustom pm-poly/python
  (pm-polymode-one "python"
                   :hostmode 'pm-host/python
                   :innermode 'pm-inner/python)
  "Python typical polymode."
  :group 'polymodes
  :type 'object)

(define-polymode poly-python-mode pm-poly/python)

C-x b test.py RET
M-x poly-python-mode RET

With this mode, triple-quoted strings are highlighted as python code. (Not normally a good idea, but you can toggle it).

Currently, polymode seems to have issues updating the font-locking. However, this should work in practice.

edited Mar 10 '16 at 03:37

answered Mar 09 '16 at 18:49

PythonNut

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I hope this works for the OP, but for me it seems to work great! You say that you can toggle it though, but how do you do that? I can toggle it on, but can't figure out how to toggle it off... – elethan Mar 10 '16 at 02:42
@elethan, as I note at the end, there seems to be some trouble relating to the font-locking when toggling. I'm looking into it, and will likely produce an issue to see if it can be resolved. – PythonNut Mar 10 '16 at 03:38
But when I say I can't toggle it off, I mean I can't figure out the command. I understand if the syntax highlighting doesn't go away, but when I call `poly-python-mode` a second time, I still see `PM` in my mode-line, indicating it is still active – elethan Mar 10 '16 at 03:44
@elethan Ah, major modes don't toggle. ;) You'll need to use `python-mode` to return to the non-polymode. – PythonNut Mar 10 '16 at 03:45
OK, switching back to `python-mode` works like a charm! I didn't realize that I had ever left python mode...(BTW, I will award the bounty once the site allows me too. Thanks for the answer...even though it isn't my question, haha!) – elethan Mar 10 '16 at 03:52
@PythonNut This is not working for me... Maybe is the issues with font-locking you mention? Which are these issues? I am using Emacs 24.3.1 – jmlorenzi Mar 10 '16 at 15:27
@jmlorenzi what exactly is the problem? If the problem is that it won't toggle on to begin with, try making a modification to the python code inside the quotes. That should force it to highlight. That's the bug I was referring to. – PythonNut Mar 10 '16 at 18:50
I see now... Indeed altering the text forces the update... it's a pity is not automatic though. Anyhow, thanks a lot for the answer!! – jmlorenzi Mar 15 '16 at 09:17

Syntax highlight narrowed python string literals as code

1 Answers1