How can I fold YAML items in VIM?

Question

I have a YAML formatted text file, and would like to define custom folding for VIM, but I'm not sure how to go about it (despite reading the VIM documentation for folding). The file consists of YAML "documents", like so:

---
title: My Title
attr1: value1
attr2: value2
---
title: Next Item
attr1: value3
---
title: One More Item
...

I would like the resulting folded text to look something like this:

+---- 2 lines: My Title ----
+---- ? lines: Next Item ---

Any suggestions are appreciated! Thanks!

score 6 · Accepted Answer · answered Jul 09 '10 at 15:13

Do

%s/---\(.*\)\(\_.\{-}title: \)\(.*\)/---\1 #{{{1 \3\2\3/g
set foldmethod=marker

or

%s/\(---\_.\{-}title: \)\(.*\)/#{{{1 \2\r\1\2/g
set foldmethod=marker

That will add comment with title to the beginning of every YAML document and leave document still valid. foldmarker option must be left untouched.

Result:

1.

--- #{{{1 My Title
title: My Title
attr1: value1
attr2: value2
--- #{{{1 Next Item
title: Next Item
attr1: value3
--- #{{{1 One More Item
title: One More Item
...

Folded:

+--  4 строк: --- My Title-----------------------------
+--  3 строк: --- Next Item----------------------------
+--  3 строк: --- One More Item------------------------

2.

#{{{1 My Title
---
title: My Title
attr1: value1
attr2: value2
#{{{1 Next Item
---
title: Next Item
attr1: value3
#{{{1 One More Item
---
title: One More Item
...

Folded:

+--  5 строк: My Title--------------------------------
+--  4 строк: Next Item-------------------------------
+--  4 строк: One More Item---------------------------

Thanks for the answer! I wasn't clear on how to use markers, and this definitely solved the problem. However, in the interest of not duplicating data, is there a way for VIM to use the regexp you gave to automatically determine fold levels, with a title? — wkranec, Jul 09 '10 at 19:59
@wkranec I think it may be done using `foldmethod=expr` with proper `foldexpr` and `foldtext` set, but I have never used it. — ZyX, Jul 10 '10 at 07:50

score 4 · Answer 2 · answered Jul 09 '10 at 12:16

4

If you want to use a foldmethod other than "manual" all the time, add this line to your ~/.vimrc:
set foldmethod=foldoption

I would recommend using foldmethod=indent. This will fold based on any indent. Then if you change your input to include the indents where you want folds to happen. For instance if you change your input to

---
title: My Title
    other attrs: other values
---
title: Next Item
---
title: One More Item
...

It will fold as you described

answered Jul 09 '10 at 12:16

Eric LaForce

2,125
15
24

Sorry about the last comment. I'm new to SO and didn't know that inline code wouldn't work (I can't edit anymore for some reason). – wkranec Jul 09 '10 at 13:50
Yeah that was my fault, I misread your original input. I was thinking it already had a nested relationship. You can use set foldmethod=marker instead. In conjunction with that you can use set foldmarker=mmm,nnn where mmm is the start marker and nnn is the ending marker. So I would try set foldmarker=---,--- (assuming --- in YAML is OK marker/delimeter for folds). Hope this helps. – Eric LaForce Jul 09 '10 at 14:05
Thanks again, Eric. I have tried the marker method before as you described, but then VIM folds the entire document (or all items until the end of the file if you try to make a fold in the middle of the document (since there really isn't a closing "---"). – wkranec Jul 09 '10 at 14:28
You can indent the whole YAML document (`---\n\ \ \ \ title: 1\n\ \ \ \ other attr: other value\n---\n\ \ \ \ title: 2\n...`), which will result in `---\n+-- 2 lines: title: 1---\n---\n+-- 2 lines: title: 2---`. And this still will be a valid YAML document, while @Eric LaForce's answer will render your document invalid. – ZyX Jul 09 '10 at 15:02

score 4 · Answer 3 · answered Nov 07 '19 at 04:11

Check out pedro's yaml-vim-plugin for improved folding that matches your exact request.

Read more about the plugin on pedro's blog or find it directly on github as pedrohdz/vim-yaml-folds

The default Vim folding rules for YAML files were always a bit of an eye strain for me. The folding commands do not behave as one would expect them to as well. More about all this in the Explanation section below.

This got me to throw together a quick and simple Vim plugin to handle YAML folding more cleanly, vim-yaml-folds. Here is what YAML folding looks like with vim-yaml-folds installed:

A fold contains the beginning of a YAML section with everything underneath it included.

If you know what I'm talking about and do not care for an explanation, feel free to skip the Explanation and install vim-yaml-folds if you would like.

How can I fold YAML items in VIM?

3 Answers3