Swish-Lint

Swish-Lint analyzes source code to flag stylistic errors, helps developers navigate code bases, and provides code completion. It provides feedback to improve code quality during development before reviews and inspections. Swish-Lint provides language features like auto completion, go to definition, and find all references to editors like Emacs and VSCode that support the Language Server Protocol.

Features include:

Code completion
Goto definition
Find references
Indentation

Install

Download a pre-built binary from the Releases page and extract the files to ~/.emacs.d/swish-lint.
Run swish-lint --version to verify that it starts properly.

Configure Emacs

Install lsp-mode 8.0.0
Install lsp-ui 8.0.0
Install flycheck - Flycheck version 31 does not work properly with lsp-mode. We recommend either using the non-stable MELPA url https://melpa.org/packages/ or another package management system to get a newer version.
Install company-mode

You may also want to follow the performance tuning instructions for lsp-mode. As as starting point, add the following to your Emacs configuration, e.g., .emacs.d/init.el or .emacs file:

(require 'flycheck)

(require 'company)
(setq company-minimum-prefix-length 1)
(setq company-idle-delay 0.0)

(require 'lsp-mode)
(setq lsp-prefer-capf t)
(setq lsp-prefer-flymake nil)
(setq lsp-enable-snippet nil)
(setq lsp-idle-delay 0.100)

(require 'lsp-ui)
(add-hook 'lsp-mode-hook 'lsp-ui-mode)
(add-hook 'scheme-mode-hook 'flycheck-mode)

(setq gc-cons-threshold 100000000)
(setq read-process-output-max (* 1024 1024))

(add-to-list 'load-path "~/.emacs.d/swish-lint")
(add-to-list 'exec-path "~/.emacs.d/swish-lint")
(require 'lsp-swish)

To use Swish-Lint's indentation, bind swish-indent-sexp in your scheme mode hook:

(add-hook 'scheme-mode-hook
  (function
   (lambda ()
     (local-set-key (kbd "C-M-q") 'swish-indent-sexp))))

Design

Swish-Lint uses a client/server architecture. The client provides the LSP support. The server maintains a central database called "The Tower". All good sourcerers keep their knowledge in a tower.

Each time you open a new project, the client scans the code for definitions and references then updates the tower. This allows features like "goto definition" to jump from one code base to another.

Swish-Lint attempts to deal with incomplete code. It reads your code using Chez Scheme's reader. When that fails, it attempts to extract identifiers using regular expressions. This means that "Find references" and highlighting may not provide lexical context or semantics you expect from the language itself.

Swish-Lint generates a set of keywords to use for completions by invoking swish, scheme, and petite stopping upon success. Swish is not required, and can be removed from your PATH to run in a "Chez Scheme-Only mode".

Diagnosing Problems

Client-side

Swish-Lint writes output to stderr which is available in a dedicated Emacs buffer. The output is helpful diagnosing protocol or performance problems.

Server-side

The tower uses an in-memory database and is automatically started when a client starts. An internal web server provides an aggregate view of client logs. See the logs here: http://localhost:51342/?limit=100

Normally the tower's database is stored in memory only. If "goto definition" or "find references" provides unexpected behavior, you can start the tower manually and write the database to disk for analysis.

The following command starts the tower, writes the database to disk, and writes diagnostic messages to the terminal:

./swish-lint --tower -v --tower-db tower.db3

Known Issues

Performance can always be improved.

"Find references" and "goto definition" apply trivial search rules. Lexical scope and language semantics are ignored.

Chez Scheme's code can fool Swish-Lint. The Chez Scheme code is complex. Swish-Lint is simple. Your mileage will vary.

becls / swish-lint