# Is there something like a "draft context" but for buffer content? **URL:** \ **Category:** Help\ **Tags:** buffer\ **Created:** [February 1, 2020, 1:04pm UTC](https://discuss.kakoune.com/t/is-there-something-like-a-draft-context-but-for-buffer-content/871 "2020-02-01T13:04:07Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Screwtapello](https://discuss.kakoune.com/user_avatar/discuss.kakoune.com/screwtapello/32/12_2.png) [@Screwtapello](https://discuss.kakoune.com/u/Screwtapello)\ **Post date:** [February 1, 2020, 1:04pm UTC](https://discuss.kakoune.com/t/is-there-something-like-a-draft-context-but-for-buffer-content/871/1 "2020-02-01T13:04:07Z")
# The problem I’ve been experimenting with a plugin to assist with local editing of GitHub wikis. The special rules for GitHub wikis are: - nearly every supported markup syntax adds support for MediaWiki-style links, so you can link to a paged named “Foo” with `[[Foo]]` - When you create a page named “Eval / Exec”, the page content is stored in a file named `Eval---Exec.md` - that is, spaces and slashes are replaced with hyphens - there may be other replaced characters too - `[[Eval / Exec]]` and `[[Eval/ /Exec]]` and `[[Eval---Exec]]` all link to the same page So when the user tries to follow a `[[Some Page]]` link, I have to map that into `Some-Page.md`, then tell Kakoune to edit the resulting file. Simple! However, it gets more complicated. For example, while GitHub squashes unsafe characters to hyphens, the Python-Markdown wiki link extension [squashes (only) spaces to underscores](https://github.com/Python-Markdown/markdown/blob/master/markdown/extensions/wikilinks.py#L26), and other wiki systems probably use other schemes, so I’d like to make the pattern and the replacement configurable. # Attempt 1 My first idea was to make a regex option for “unsafe character pattern”, and a string option for “unsafe character replacement”, and then my code would use `sed` to process the page name and produce a filename for Kakoune to edit. However, a Kakoune regex option validates against _Kakoune’s_ regex syntax, not sed’s, and it felt silly to have Kakoune (a mighty text-processing tool) shell out to a simple text-processing tool just to do a search-and-replace. # Attempt 2 My second idea was to have the “squash unsafe characters” option be a _command_ rather than a pattern and a replacement, and I’d use it something like this: ``` # kakrc set global wiki_squash_unsafe_characters "exec s[/]c-" # in my plugin eval -draft %opt{wiki_squash_unsafe_characters} wiki-edit-page-named %val{selection} ``` …except that the `wiki_squash_unsafe_characters` command modifies the buffer! So let’s put an undo after it: ``` eval -draft %opt{wiki_squash_unsafe_characters} wiki-edit-page-named %val{selection} exec u ``` …except that `wiki-edit-page-named` is going to _change_ which buffer is active, and the undo is going to go to the wrong buffer! That’s OK, we can work with that: ``` eval -save-regs b %{ reg b %val{buffile} eval -draft %opt{wiki_squash_unsafe_characters} wiki-edit-page-named %val{selection} exec -buffer %reg{b} u } ``` …except that it’s possible to have a page name _without_ any unsafe characters, like `[[Home]]`, in which case `wiki_squash_unsafe_characters` is going to throw an error. Well, we can fix that with a `try` command: ``` eval -save-regs b %{ reg b %val{buffile} try %{ eval -draft %opt{wiki_squash_unsafe_characters} wiki-edit-page-named %val{selection} exec -buffer %reg{b} u } catch %{ wiki-edit-page-named %val{selection} } } ``` …and that works. Unfortunately, it means that `wiki_squash_unsafe_characters` must do exactly one undoable operation, no more or less, and it means that any legitimate errors in `wiki-edit-page-named` will become very difficult to debug, and leave the buffer in an inconsistent state (with the squash action not undone). # What (I think) I want, option 1 There should be something that’s like `eval -draft`, but it restores buffer content afterward, or copies the buffer into a temporary scratch buffer or something. If such an option existed — let’s call it `-scratch` — my code could look like this: ``` evaluate-commands -scratch %{ try %{ eval -draft %opt{wiki_squash_unsafe_characters} } wiki-edit-page-named %val{selection} } ``` Much simpler, and more reliable! # What (I think) I want, option 2 Alternatively, and perhaps simpler to implement, would be a way to navigate through the history tree to a specific point. `` and `` step along one branch of the undo tree, while `` and `` step between branches, but imagine there was some other binding like `` that took you straight to the history node whose number was given by the count. Then my code could look like this: ``` eval -save-regs bh %{ reg b %val{buffile} reg h %val{history_id} try %{ eval -draft %opt{wiki_squash_unsafe_characters} } wiki-edit-page-named %val{selection} exec -buffer %reg{b} %reg{h} } ``` Not quite as clean as the previous idea, but still nicer than what I’m using currently. # Conclusion Are there any Kakoune features I’ve missed that would help me out with this? Is there a better approach I could be taking? ---
**Author:** ![prion](https://discuss.kakoune.com/user_avatar/discuss.kakoune.com/prion/32/404_2.png) [@prion](https://discuss.kakoune.com/u/prion)\ **Post date:** [February 2, 2020, 10:44pm UTC](https://discuss.kakoune.com/t/is-there-something-like-a-draft-context-but-for-buffer-content/871/2 "2020-02-02T22:44:23Z")
I also think Kakoune would benefit from having better ways to view the history tree, which would also require new commands to navigate it. But WRT to option one I can’t think of any reason you can’t do this with existing commands, even though a built in short cut might be nice. Just open a scratch buffer with `:edit -scratch` and copy the pre-edit line to it. But an easier solution is just to copy the edit to a register and evaluate it’s contents after the undo. ```auto eval -draft %opt{wiki_squash_unsafe_characters} # this can all be done in eval -draft command but wrote it out explicitly here to demonstrate reg m %val{selection} exec u # navigate to the edited line that was saved to a register. exec ': wiki-edit-page-named %reg{m} ```