electric-quote-mode support

[jacksonrayhamilton]

I tried using Emacs 25's new electric-quote-mode with this mode, but my quote characters don't seem to be transformed.

I opened a .md file in this mode and enabled electric-quote-mode, and typed:

`And I said,' 
``Hello World!''

I expected it to become:

‘And I said,’
“Hello World!”

If I open a .c file and type the same thing into a comment, the quote characters are transformed. So it seems to be an issue with this mode.

The docs for electric-quote-mode say,

This occurs only in comments, strings, and text paragraphs . . .

Maybe markdown-mode paragraphs are not being considered proper "paragraphs" by Emacs?

[legends2k]

I'm affected by this too. However, this mightn't be easy since ` is used for inline code spans in Markdown; incorporating this will have wrinkles in the workflow.

[jrblevin]

I didn't know about electric-quote-mode, but it would be nice to support. The major problem would be the conflict with the ` character, which is important in Markdown for inline code and code blocks. I'm not sure how to easily distinguish between the two intents: starting a code fragment or opening a quotation.

I did, however, manage to figure out why electric-quote-mode refuses to operate in markdown-mode: there is a condition in electric-quote-post-self-insert-function that checks to see if comment-start is non-nil. markdown-mode does define a comment syntax (HTML comments), as opposed to text-mode, which has no comment syntax. Because of that, electric-quote-mode only wants to operate inside of comments and strings (as would be entirely appropriate for most programming modes). So, if you start a comment in markdown-mode with <!-- then electric-quote-mode will work as expected.

Due to the way electric-quote-mode is implemented, I don't see a way around this other than re-implementing the behavior in markdown-mode, but then there is the ` conflict to deal with.

[jacksonrayhamilton]

there is a condition in electric-quote-post-self-insert-function that checks to see if comment-start is non-nil

It sounds like electric-quote-mode is "duck-typing" "text" vs "programming" modes based on the existence of comment syntax. Maybe electric-quote-mode should be updated so that we can hint to it that our mode is sort of a "hybrid text and programming mode" and should support both types of transformations.

To deal with the backtick conflict, maybe electric-quote-mode should be able to retroactively transform the quotes only if it sees that a backtick and an apostrophe match. The markdown syntax for inline code spans are matching backticks, so they could be differentiated at that point.

[phst]

FYI, a while ago I've filed https://debbugs.gnu.org/cgi/bugreport.cgi?bug=24709 against Emacs that also touches on some of these points.

[phst]

The original issue should be fixable by setting comment-use-syntax to nil (#213). That doesn't fix the clash between electric quote and code start for the backtick, though.

[jrblevin]

I see that if comment-use-syntax was nil, that would fix the issue. However, markdown-mode does use the syntax table for comments and so setting it to nil would be incorrect. I think we're back to this being an issue with the assumptions of electric-quote-mode about modes that define comment syntax.

[phst]

You're right; probably electric-quote-mode should just treat text-mode as a stronger signal than comment syntax.

[phst]

I've now pushed a series of patches to Emacs to improve compatibility. Specifically, electric-quote-mode now checks text-mode first, and there's a special hook electric-quote-inhibit-functions to selectively inhibit electric quoting, which could be used for code spans and blocks.

[jrblevin]

This is great; thanks for your work on both Emacs and markdown-mode on this front. I just merged #220.

[jrblevin]

I verified that electric-quote-mode is working as expected with markdown-mode using a recent Emacs 26 pretest build, thanks to the patches by @phst, so I'll close this now.