Lissy

Structural editing for Fennel.

Heavily inspired by the Emacs package lispy. Have a look at its README for an overview of theoretically possible commands, of which most are not (yet) implemented here. And those that are behave slightly differently. Have fun!

Status

Experimental.

Currently, fennel is the only supported language. But it should not be hard to add support for other Lisp-like languages in the future.

This extension does not add Fennel language support. Another extension is required! For example kongeor.vsc-fennel, or adjuvant.fennel-syntax

Most of the heavy lifting is done by tree-sitter with a simple s-expression grammar for Fennel. The simple grammar wont provide much detail about the code, but is much more error resistant, than a complete Fennel grammar. Only worry about unterminated strings.

Command reference

I am too lazy to list all commands here. And would probably forget to update this list anyway. Please have a look at the source code instead: https://codeberg.org/adjuvant/vscode-lissy/src/branch/main/src/keymap.ts

You can read more about how the commands should behave in the Lispy function reference: http://oremacs.com/lispy/

Warning: VSCode 'type' command

This extension registers the special type command. Only one extension can do that at a time. But, as far as I am aware, this is the only way to bind to non-alphanumeric characters (independent of keyboard layout).

TODO: Do not register type command if no keybindings are configured. That is base-keymap is set to none and global-keys and special-keys are empty.

Configuration

Two keymaps:

global: always active
special: only active if the the point is special (e.g. before or after parens)

For example: To remove the default mapping of [, and override the mapping of ] and add a mapping for }:

  "lissy.global-keys": {
    "[": null,
    "]": "lissy.backward",
    "}": "lissy.forward"
  },

You can also bind lissy. commands to normal VSCode hotkeys. Just make sure to add "when": "editorTextFocus && editorLangId === fennel"

To deactivate the default mappings, set lissy.base-keymap to "none".

Known problems

It is not possible to directly replace selected text by typing. As some keys would trigger lissy special commands. Delete the existing text first.
lissy.comment comments whole lines, causing collateral damage.
lissy.indent does not yet work in combination with multi-line strings
lissy.indent indents all "macro bodies" the same way. That is, if and do indentation is identical to fn and λ, which can be wrong:
```
(if (= a 2)
  true
  (= a 3)
  3)
```
```
(do (set a 1)
  (set b 2))
```

Differences to lispy

lissy.indent instead of lispy-tab, only indents, nothing else.

TODO

Fix: Cursor before : in (foo:bar 42) should not be special
Fix: trailing parens cause indent to do weird things (and trailing parens are not indented at all)
Fix: indent of do: indent first arg by 2, and others aligned to first
kill, yank, copy, paste, kill ring
multi-line, single-line
implement more of Lispy's commands
implement Lispy's arg count, repeated commands
write tests for command logic
movement commands with regions (selections) should keep them active
multiple selections
highlight selected sexp
automatic indentation

Development

Start the "Run Extension" task in vscode (F5)

The npm run watch default build task should start automatically in the background.

Installation

npm install --ignore-scripts
npx vsce package
codium --install-extension lissy-x.y.z.vsix

Source

The source code of this extension is available at https://codeberg.org/adjuvant/vscode-lissy

License

The source code of this extension is licensed under the Mozilla Public License Version 2.0. See file LICENSE.

See grammars/ for bundled grammars and their licenses.

tree-sitter-fennel : MIT