Formatter & linter

super-slim format [PATH…]           # rewrite templates in place
super-slim format --check [PATH…]   # list the ones it would rewrite, exit 1 if any

One layout: two spaces per level, - code and = output spacing, p = output after a tag, no redundant div, no trailing whitespace, single blank lines, one final newline. Text blocks move as a whole, so the whitespace they render stays put.

Before writing a file, the formatter compiles the template before and after, and refuses if the Ruby differs: formatting cannot change a page. A refused file is reported and left untouched, and the command exits 1.

With format: max_line_length in .super-slim.yml, longer lines are wrapped: a tag’s attributes one per line inside attribute_delimiters (() by default, or [], {}), then the arguments of its Ruby code after each comma, which Slim reads as a line that goes on. When the line opens a block, its arguments go four spaces deeper, apart from the block’s children. Lines already spread over several lines stay as they are, and a wrap is only kept when Prism reads the same compiled Ruby.

a.btn(
  href=edit_post_path(post)
  data-turbo-frame="modal"
) = t ".edit",
  title: post.title

Paths default to the current directory; .git, node_modules, tmp and vendor are skipped.

$ super-slim lint [PATH…]
app/views/posts/_card.html.slim:3: [ImageAlt] Describe the image with `alt`, or mark it decorative with `alt=""`

33 rules taken from slim-lint, haml-lint, erb_lint, Herb and eslint-plugin-jsx-a11y: layout, template hygiene, Ruby in templates, Rails conventions, HTML and accessibility. It exits 1 when it reports an offense.

The Ruby inside templates is RuboCop’s job. SuperSlim ships a RuboCop plugin that hands it each - and = line, code attribute, splat, #{} interpolation and ruby: block, read by SuperSlim’s own parser:

# .rubocop-slim.yml
inherit_from: .rubocop.yml
plugins:
  - super-slim
AllCops:
  Include:
    - "**/*.slim"

$ bundle exec rubocop -c .rubocop-slim.yml app
app/views/posts/show.html.slim:4:20: C: [Correctable] Style/StringLiterals: Prefer single-quoted strings…

Offenses point at their line and column in the .slim file, and --autocorrect writes back into it. The cops that cannot hold in a template, such as indentation across lines or frozen string comments, are off for .slim files. It replaces rubocop-slim, and with it slimi and Temple.

Both commands read .super-slim.yml from the current directory. Every key is optional:

tailwind_classes: true     # read templates the way the app compiles them

format:
  max_line_length: 120     # wrap longer lines, default off
  attribute_delimiters: "{}" # around wrapped attributes: "()", "[]" or "{}", default "()"

linters:
  LineLength:
    max: 150                 # default 120
  ConsecutiveControlStatements:
    max: 3                   # lines of `-` before asking for a ruby: block, default 2
  ButtonType:
    enabled: true            # off by default: ButtonType, EmbeddedEngines, HardcodedText, InlineStyles, StrictLocals, UnescapedOutput
  DeprecatedClasses:
    preset: bootstrap5       # Bootstrap 4 classes that Bootstrap 5.3 renamed or dropped
    classes:
      media: ~               # drops an entry of the preset
      legacy-*: modern-*     # a prefix: legacy-card becomes modern-card
  DeprecatedAttributes:
    preset: bootstrap5       # data-toggle becomes data-bs-toggle, and so on
  EmbeddedEngines:
    enabled: true
    forbidden_engines: [javascript, css]
  HardcodedText:
    enabled: true
    include: ["app/views/shop/**/*.slim"]   # every rule takes include: and exclude: globs
  InlineStyles:
    enabled: true
    exclude: ["app/views/*_mailer/**/*"]   # relative to .super-slim.yml
  InstanceVariables:
    enabled: false

# .github/workflows/lint.yml
- run: bundle exec super-slim format --check app
- run: bundle exec super-slim lint app
- run: bundle exec rubocop -c .rubocop-slim.yml app

Both print one line per file or offense, path:line: [Rule] message for the linter, and exit 0 when there is nothing to report, 1 otherwise, 64 on a usage error.