Linter Rules

This page contains documentation for all Herb Linter rules.

Available Rules

Accessibility

• a11y-avoid-generic-link-text - Avoid generic link text like "Click here" or "Read more"
• a11y-disabled-attribute - Prevent usage of the disabled attribute on unsupported elements
• a11y-nested-interactive-elements - Disallow nesting interactive elements
• a11y-no-accesskey-attribute - Prevent usage of the accesskey attribute
• a11y-no-aria-label-misuse - Prevent aria-label and aria-labelledby on non-interactive elements
• a11y-no-aria-unsupported-elements - Prevent usage of ARIA on unsupported elements
• a11y-no-autofocus-attribute - Prevent usage of the autofocus attribute
• a11y-no-redundant-image-alt - Prevent redundant words in <img> alt attributes
• a11y-svg-has-accessible-text - Require accessible text on <svg> elements

Action View

• actionview-no-helper-shadowing - Disallow shadowing Action View helpers with block variables
• actionview-no-implicit-polymorphic-url - Prefer explicit route helpers over implicit polymorphic URLs
• actionview-no-redundant-local-assigns - Disallow local_assigns reads that the strict locals declaration already answers
• actionview-no-silent-helper - Disallow silent ERB tags for Action View helpers
• actionview-no-silent-render - Disallow calling render without outputting the result
• actionview-no-unnecessary-html-safe - Disallow calling .html_safe on String literals
• actionview-no-unnecessary-tag-attributes - Disallow unnecessary attributes on Action View tag helpers
• actionview-no-unused-strict-locals - Disallow strict locals that are never used in the partial
• actionview-no-void-element-content - Disallow content arguments for void Action View elements
• actionview-prefer-collection-render - Prefer collection rendering over rendering a partial in a loop
• actionview-strict-locals-first-line - Require strict locals on the first line of partials with a blank line after.
• actionview-strict-locals-partial-only - Only allow strict local definitions in partial files.

ERB

• erb-comment-syntax - Disallow Ruby comments immediately after ERB tags
• erb-no-case-node-children - Don't use children for case/when and case/in nodes
• erb-no-commented-out-output-tags - Disallow commented-out ERB output tags (<%#=, <%# =)
• erb-no-debug-output - Disallow debug output methods (p, pp, puts, print, debug) in ERB templates
• erb-no-conditional-html-element - Disallow conditional HTML elements
• erb-no-conditional-open-tag - Disallow conditional HTML open tags
• erb-no-duplicate-branch-elements - Disallow duplicate elements across conditional branches
• erb-no-empty-control-flow - Disallow empty ERB control flow blocks
• erb-no-empty-tags - Disallow empty ERB tags
• erb-no-extra-newline - Disallow extra newlines.
• erb-no-extra-whitespace-inside-tags - Disallow multiple consecutive spaces inside ERB tags
• erb-no-inline-case-conditions - Disallow inline case/when and case/in conditions in a single ERB tag
• erb-no-instance-variables-in-partials - Disallow instance variables in partials
• erb-no-interpolated-class-names - Disallow ERB interpolation inside CSS class names
• erb-no-javascript-tag-helper - Disallow javascript_tag helper
• erb-no-output-control-flow - Prevents outputting control flow blocks
• erb-no-output-in-attribute-name - Disallow ERB output in attribute names
• erb-no-output-in-attribute-position - Disallow ERB output in attribute position
• erb-no-raw-output-in-attribute-value - Disallow <%== in attribute values
• erb-no-shadowed-block-argument - Disallow block arguments that shadow an enclosing binding
• erb-no-silent-statement - Disallow silent ERB statements
• erb-no-silent-tag-in-attribute-name - Disallow ERB silent tags in HTML attribute names
• erb-no-sleep - Disallow sleep in ERB templates
• erb-no-statement-in-script - Disallow ERB statements inside <script> tags
• erb-no-then-in-control-flow - Disallow then in ERB control flow expressions
• erb-no-trailing-whitespace - Disallow trailing whitespace at end of lines.
• erb-no-unsafe-js-attribute - Disallow unsafe ERB output in JavaScript attributes
• erb-no-unsafe-raw - Disallow raw() and .html_safe in ERB output
• erb-no-unsafe-script-interpolation - Disallow unsafe ERB output inside <script> tags
• erb-no-unused-block-argument - Disallow unused block arguments in ERB blocks
• erb-no-unused-expressions - Disallow unused expressions in silent ERB tags
• erb-no-unused-literals - Disallow Ruby literals in ERB without output
• erb-prefer-direct-output - Prefer direct ERB output over string interpolation
• erb-prefer-do-end-blocks - Prefer do ... end over { ... } for blocks that span multiple ERB tags
• erb-prefer-each-over-map - Prefer each over map when the result is discarded
• erb-prefer-explicit-conditionals - Prefer explicit if/unless blocks over inline conditions in ERB output tags
• erb-prefer-image-tag-helper - Prefer image_tag helper over <img> with ERB expressions
• erb-require-trailing-newline - Enforces that all HTML+ERB template files end with exactly one trailing newline character.
• erb-require-whitespace-inside-tags - Requires whitespace around ERB tags
• erb-right-trim - Enforce consistent right-trimming syntax.
• erb-strict-locals-comment-syntax - Enforce strict locals comment syntax.
• erb-strict-locals-required - Require strict locals in Rails partials.

Herb

• herb-disable-comment-malformed - Detect malformed herb:disable comments.
• herb-disable-comment-missing-rules - Require rule names in herb:disable comments.
• herb-disable-comment-no-duplicate-rules - Disallow duplicate rule names in herb:disable comments.
• herb-disable-comment-no-redundant-all - Disallow redundant use of all in herb:disable comments.
• herb-disable-comment-unnecessary - Detect unnecessary herb:disable comments.
• herb-disable-comment-valid-rule-name - Validate rule names in herb:disable comments.

HTML

• html-allowed-script-type - Restrict allowed type attributes for <script> tags
• html-anchor-require-href - Requires an href attribute on anchor tags
• html-aria-attribute-must-be-valid - Disallow invalid or unknown aria-* attributes.
• html-aria-label-is-well-formatted - aria-label must be well-formatted
• html-aria-level-must-be-valid - aria-level must be between 1 and 6
• html-aria-role-heading-requires-level - Requires aria-level when supplying a role
• html-aria-role-must-be-valid - The role attribute must have a valid WAI-ARIA Role.
• html-attribute-double-quotes - Enforces double quotes for attribute values
• html-attribute-equals-spacing - No whitespace around = in HTML attributes
• html-attribute-values-require-quotes - Requires quotes around attribute values
• html-avoid-both-disabled-and-aria-disabled - Avoid using both disabled and aria-disabled attributes
• html-body-only-elements - Require content elements inside <body>.
• html-boolean-attributes-no-value - Prevents values on boolean attributes
• html-details-has-summary - Require <summary> in <details> elements
• html-head-only-elements - Require head-scoped elements inside <head>.
• html-iframe-has-title - iframe elements must have a title attribute
• html-img-require-alt - Requires alt attributes on <img> tags
• html-input-require-autocomplete - Require autocomplete attributes on <input> tags.
• html-navigation-has-label - Navigation landmarks must have accessible labels
• html-no-abstract-roles - No abstract ARIA roles
• html-no-aria-hidden-on-body - No aria-hidden on <body>
• html-no-aria-hidden-on-focusable - Focusable elements should not have aria-hidden="true"
• html-no-block-inside-inline - Prevents block-level elements inside inline elements
• html-no-duplicate-attributes - Prevents duplicate attributes on HTML elements
• html-no-duplicate-ids - Prevents duplicate IDs within a document
• html-no-duplicate-meta-names - Duplicate <meta> name attributes are not allowed.
• html-no-empty-attributes - Attributes must not have empty values
• html-no-empty-headings - Disallow empty heading elements
• html-no-nested-forms - Prevents nested form elements, including Rails form helpers
• html-no-nested-links - Prevents nested anchor tags
• html-no-positive-tab-index - Avoid positive tabindex values
• html-no-self-closing - Disallow self closing tags
• html-no-unescaped-entities - Disallow unescaped HTML entities
• html-no-unknown-tag - Disallow unknown HTML tags
• html-no-space-in-tag - Disallow spaces in HTML tags
• html-no-title-attribute - Avoid using the title attribute
• html-no-underscores-in-attribute-names - Disallow underscores in HTML attribute names
• html-require-closing-tags - Require closing tags for non-void HTML elements
• html-require-script-nonce - Require nonce attribute on script tags and helpers
• html-tag-name-lowercase - Enforces lowercase tag names in HTML

Parser

• parser-no-errors - Disallow parser errors in HTML+ERB documents

Source

• source-indentation - Indent with spaces instead of tabs.

SVG

• svg-tag-name-capitalization - Enforces proper camelCase capitalization for SVG elements

Turbo

• turbo-permanent-no-misleading-value - Disallow misleading values on data-turbo-permanent
• turbo-permanent-require-id - Require id attribute on elements with data-turbo-permanent

Contributing

To add a new linter rule:

1. Create the rule class implementing the Rule interface
2. Add comprehensive tests in test/rules/
3. Add documentation in docs/rules/
4. Update the main linter to include the rule by default (if appropriate)

See html-tag-name-lowercase.ts for an example implementation.