[vim/vim] Syntax concealing not rendered when foldmethod=diff has closed folds (Issue #19423)
sideshowbarker
sideshowbarker created an issue (vim/vim#19423)Problem
Syntax concealing does not render on visible (unfolded) lines when foldmethod=diff is active and some folds are closed. The conceal rules are correctly defined and conceallevel is set, but the concealed text is displayed literally.
Opening all folds (zR), forcing a redraw, then re-closing them (zM) causes concealing to render correctly.
Steps to reproduce
set nocompatible syntax on enew setlocal buftype=nofile bufhidden=wipe call setline(1, [ \ 'Same 1', 'Same 2', 'Same 3', \ 'Left only [visible](http://hidden-url)', \ 'Same 5', 'Same 6', \ ]) setlocal syntax=markdown conceallevel=2 diffthis vnew setlocal buftype=nofile bufhidden=wipe call setline(1, [ \ 'Same 1', 'Same 2', 'Same 3', \ 'Right only [visible](http://hidden-url)', \ 'Same 5', 'Same 6', \ ]) setlocal syntax=markdown conceallevel=2 diffthis
Expected behavior
Line 4 in both buffers should show the markdown link with the URL concealed (i.e., just “visible” instead of “visible”).
Actual behavior
Line 4 shows the raw markdown [visible](http://hidden-url) with no concealing applied, even though conceallevel=2 and the syntax conceal rules are active.
Workaround
After diffthis, running zR (open all folds), redraw, then zM (close all folds) causes concealing to render correctly. This can be automated with a deferred callback:
timer_start(50, (_) => { normal! zR redraw normal! zM })
The redraw between zR and zM is essential — without it, the workaround has no effect.
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zeertzjq
zeertzjq left a comment (vim/vim#19423)The conceal rules are correctly defined
Where do the conceal rules come from? The builtin markdown syntax file doesn't conceal URLs.
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sideshowbarker
sideshowbarker left a comment (vim/vim#19423)The conceal rules come from preservim/vim-markdown, which provides a syntax/markdown.vim that includes conceal on inline link URLs and other elements. The built-in syntax file doesn't conceal, correct.
But the bug isn't specific to any particular conceal rules — it's that foldmethod=diff with closed folds prevents any syntax concealing from rendering on visible (unfolded) lines. Here's a self-contained reproduction using a custom syntax rule with no plugins:
set nocompatible syntax on " Left buffer enew setlocal buftype=nofile bufhidden=wipe call setline(1, ['Same 1', 'Same 2', 'Same 3', 'Left SECRET here', 'Same 5', 'Same 6']) syntax match MySecret /SECRET/ conceal setlocal conceallevel=2 diffthis " Right buffer vnew setlocal buftype=nofile bufhidden=wipe call setline(1, ['Same 1', 'Same 2', 'Same 3', 'Right SECRET here', 'Same 5', 'Same 6']) syntax match MySecret /SECRET/ conceal setlocal conceallevel=2 diffthis
Expected: SECRET is concealed on line 4 in both buffers.
Actual: SECRET is shown literally. Running zR then zM makes concealing appear.
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zeertzjq
zeertzjq left a comment (vim/vim#19423)Cannot reproduce. The script doesn't lead to any closed folds.
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sideshowbarker
sideshowbarker left a comment (vim/vim#19423)Updated the reproduction script — the previous one had too few lines to form closed folds. Here's an updated version with enough unchanged lines:
set nocompatible syntax on let shared_before = map(range(1, 20), '"Same " .. v:val') let shared_after = map(range(1, 20), '"After " .. v:val') " Left buffer enew setlocal buftype=nofile bufhidden=wipe call setline(1, shared_before + ['Left SECRET here'] + shared_after)
syntax match MySecret /SECRET/ conceal setlocal conceallevel=2 diffthis " Right buffer
vnew setlocal buftype=nofile bufhidden=wipe call setline(1, shared_before + ['Right SECRET here'] + shared_after)
syntax match MySecret /SECRET/ conceal setlocal conceallevel=2 diffthis
With 20 unchanged lines on each side, foldmethod=diff creates closed folds. Line 21 (the changed line) is visible but SECRET is not concealed. Running zR then zM makes concealing appear.
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Christian Brabandt
chrisbra left a comment (vim/vim#19423)Works as expected, using vim --clean -u script.vim
image.png (view on web)—
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sideshowbarker
sideshowbarker left a comment (vim/vim#19423)Works as expected, using vim --clean -u script.vim
OK, yeah, I can’t reproduce it with --clean, either.
So I guess there’s something else going on in my environment — and given that, I’m gonna close this and regroup and try to further isolate the problem.
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sideshowbarker
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sideshowbarker
sideshowbarker left a comment (vim/vim#19423)And now I realize I should have rightly closed this as “not planned / can’t repro”. But it seems the repo perms don’t allow me to reopen it. So please re-open and re-close it as such — if the normal project policy/convention is to do that.
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zeertzjq
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