Linter: Implement actionview-no-silent-helper rule

javascript/packages/linter/docs/rules/README.md

@@ -4,6 +4,7 @@ This page contains documentation for all Herb Linter rules.
 
 ## Available Rules
 
+- [`actionview-no-silent-helper`](./actionview-no-silent-helper.md) - Disallow silent ERB tags for Action View helpers
 - [`erb-comment-syntax`](./erb-comment-syntax.md) - Disallow Ruby comments immediately after ERB tags
 - [`erb-no-case-node-children`](./erb-no-case-node-children.md) - Don't use `children` for `case/when` and `case/in` nodes
 - [`erb-no-conditional-html-element`](./erb-no-conditional-html-element.md) - Disallow conditional HTML elements

javascript/packages/linter/docs/rules/actionview-no-silent-helper.md

@@ -0,0 +1,57 @@
+# Linter Rule: Disallow silent ERB tags for Action View helpers
+
+**Rule:** `actionview-no-silent-helper`
+
+## Description
+
+Action View helpers like `link_to`, `form_with`, and `content_tag` must use output ERB tags (`<%= %>`) so their rendered HTML is included in the page. Using silent ERB tags (`<% %>`) discards the helper's output entirely.
+
+## Rationale
+
+Action View helpers generate HTML that needs to be rendered into the template. When a helper is called with a silent ERB tag (`<% %>`), the return value is evaluated but silently discarded, meaning the generated HTML never appears in the output. This is almost always a mistake and can lead to confusing bugs where elements are missing from the page with no obvious cause. Using `<%= %>` ensures the helper's output is properly rendered.
+
+## Examples
+
+### ✅ Good
+
+```erb
+<%= link_to "Home", root_path %>
+```
+
+```erb
+<%= form_with model: @user do |f| %>
+  <%= f.text_field :name %>
+<% end %>
+```
+
+```erb
+<%= button_to "Delete", user_path(@user), method: :delete %>
+```
+
+```erb
+<%= content_tag :div, "Hello", class: "greeting" %>
+```
+
+### 🚫 Bad
+
+```erb
+<% link_to "Home", root_path %>
+```
+
+```erb
+<% form_with model: @user do |f| %>
+  <%= f.text_field :name %>
+<% end %>
+```
+
+```erb
+<% button_to "Delete", user_path(@user), method: :delete %>
+```
+
+```erb
+<% content_tag :div, "Hello", class: "greeting" %>
+```
+
+## References
+
+* [Rails Action View Helpers documentation](https://api.rubyonrails.org/classes/ActionView/Helpers.html)

javascript/packages/linter/src/rules.ts

@@ -1,41 +1,43 @@
 import type { RuleClass } from "./types.js"
 
+import { ActionViewNoSilentHelperRule } from "./rules/actionview-no-silent-helper.js"
+
 import { ERBCommentSyntax } from "./rules/erb-comment-syntax.js";
 import { ERBNoCaseNodeChildrenRule } from "./rules/erb-no-case-node-children.js"
-import { ERBNoInlineCaseConditionsRule } from "./rules/erb-no-inline-case-conditions.js"
 import { ERBNoConditionalHTMLElementRule } from "./rules/erb-no-conditional-html-element.js"
-import { ERBNoDuplicateBranchElementsRule } from "./rules/erb-no-duplicate-branch-elements.js"
 import { ERBNoConditionalOpenTagRule } from "./rules/erb-no-conditional-open-tag.js"
+import { ERBNoDuplicateBranchElementsRule } from "./rules/erb-no-duplicate-branch-elements.js"
 import { ERBNoEmptyTagsRule } from "./rules/erb-no-empty-tags.js"
-import { ERBNoInterpolatedClassNamesRule } from "./rules/erb-no-interpolated-class-names.js"
 import { ERBNoExtraNewLineRule } from "./rules/erb-no-extra-newline.js"
 import { ERBNoExtraWhitespaceRule } from "./rules/erb-no-extra-whitespace-inside-tags.js"
-import { ERBNoOutputControlFlowRule } from "./rules/erb-no-output-control-flow.js"
-import { ERBNoThenInControlFlowRule } from "./rules/erb-no-then-in-control-flow.js"
-import { ERBNoSilentTagInAttributeNameRule } from "./rules/erb-no-silent-tag-in-attribute-name.js"
-import { ERBNoTrailingWhitespaceRule } from "./rules/erb-no-trailing-whitespace.js"
-import { ERBPreferImageTagHelperRule } from "./rules/erb-prefer-image-tag-helper.js"
-import { ERBRequireTrailingNewlineRule } from "./rules/erb-require-trailing-newline.js"
-import { ERBRequireWhitespaceRule } from "./rules/erb-require-whitespace-inside-tags.js"
+import { ERBNoInlineCaseConditionsRule } from "./rules/erb-no-inline-case-conditions.js"
+import { ERBNoInstanceVariablesInPartialsRule } from "./rules/erb-no-instance-variables-in-partials.js"
+import { ERBNoInterpolatedClassNamesRule } from "./rules/erb-no-interpolated-class-names.js"
 import { ERBNoJavascriptTagHelperRule } from "./rules/erb-no-javascript-tag-helper.js"
+import { ERBNoOutputControlFlowRule } from "./rules/erb-no-output-control-flow.js"
+import { ERBNoOutputInAttributeNameRule } from "./rules/erb-no-output-in-attribute-name.js"
+import { ERBNoOutputInAttributePositionRule } from "./rules/erb-no-output-in-attribute-position.js"
 import { ERBNoRawOutputInAttributeValueRule } from "./rules/erb-no-raw-output-in-attribute-value.js"
+import { ERBNoSilentTagInAttributeNameRule } from "./rules/erb-no-silent-tag-in-attribute-name.js"
 import { ERBNoStatementInScriptRule } from "./rules/erb-no-statement-in-script.js"
+import { ERBNoThenInControlFlowRule } from "./rules/erb-no-then-in-control-flow.js"
+import { ERBNoTrailingWhitespaceRule } from "./rules/erb-no-trailing-whitespace.js"
 import { ERBNoUnsafeJSAttributeRule } from "./rules/erb-no-unsafe-js-attribute.js"
 import { ERBNoUnsafeRawRule } from "./rules/erb-no-unsafe-raw.js"
 import { ERBNoUnsafeScriptInterpolationRule } from "./rules/erb-no-unsafe-script-interpolation.js"
+import { ERBPreferImageTagHelperRule } from "./rules/erb-prefer-image-tag-helper.js"
+import { ERBRequireTrailingNewlineRule } from "./rules/erb-require-trailing-newline.js"
+import { ERBRequireWhitespaceRule } from "./rules/erb-require-whitespace-inside-tags.js"
 import { ERBRightTrimRule } from "./rules/erb-right-trim.js"
-import { ERBNoOutputInAttributePositionRule } from "./rules/erb-no-output-in-attribute-position.js"
-import { ERBNoOutputInAttributeNameRule } from "./rules/erb-no-output-in-attribute-name.js"
 import { ERBStrictLocalsCommentSyntaxRule } from "./rules/erb-strict-locals-comment-syntax.js"
-import { ERBNoInstanceVariablesInPartialsRule } from "./rules/erb-no-instance-variables-in-partials.js"
 import { ERBStrictLocalsRequiredRule } from "./rules/erb-strict-locals-required.js"
 
-import { HerbDisableCommentValidRuleNameRule } from "./rules/herb-disable-comment-valid-rule-name.js"
-import { HerbDisableCommentNoRedundantAllRule } from "./rules/herb-disable-comment-no-redundant-all.js"
-import { HerbDisableCommentNoDuplicateRulesRule } from "./rules/herb-disable-comment-no-duplicate-rules.js"
-import { HerbDisableCommentMissingRulesRule } from "./rules/herb-disable-comment-missing-rules.js"
 import { HerbDisableCommentMalformedRule } from "./rules/herb-disable-comment-malformed.js"
+import { HerbDisableCommentMissingRulesRule } from "./rules/herb-disable-comment-missing-rules.js"
+import { HerbDisableCommentNoDuplicateRulesRule } from "./rules/herb-disable-comment-no-duplicate-rules.js"
+import { HerbDisableCommentNoRedundantAllRule } from "./rules/herb-disable-comment-no-redundant-all.js"
 import { HerbDisableCommentUnnecessaryRule } from "./rules/herb-disable-comment-unnecessary.js"
+import { HerbDisableCommentValidRuleNameRule } from "./rules/herb-disable-comment-valid-rule-name.js"
 
 import { HTMLAllowedScriptTypeRule } from "./rules/html-allowed-script-type.js"
 import { HTMLAnchorRequireHrefRule } from "./rules/html-anchor-require-href.js"
@@ -72,49 +74,52 @@ import { HTMLNoTitleAttributeRule } from "./rules/html-no-title-attribute.js"
 import { HTMLNoUnderscoresInAttributeNamesRule } from "./rules/html-no-underscores-in-attribute-names.js"
 import { HTMLRequireClosingTagsRule } from "./rules/html-require-closing-tags.js"
 import { HTMLTagNameLowercaseRule } from "./rules/html-tag-name-lowercase.js"
-import { TurboPermanentRequireIdRule } from "./rules/turbo-permanent-require-id.js"
+
+import { ParserNoErrorsRule } from "./rules/parser-no-errors.js"
 
 import { SVGTagNameCapitalizationRule } from "./rules/svg-tag-name-capitalization.js"
 
-import { ParserNoErrorsRule } from "./rules/parser-no-errors.js"
+import { TurboPermanentRequireIdRule } from "./rules/turbo-permanent-require-id.js"
 
 export const rules: RuleClass[] = [
+  ActionViewNoSilentHelperRule,
+
   ERBCommentSyntax,
   ERBNoCaseNodeChildrenRule,
-  ERBNoInlineCaseConditionsRule,
   ERBNoConditionalHTMLElementRule,
-  ERBNoDuplicateBranchElementsRule,
   ERBNoConditionalOpenTagRule,
+  ERBNoDuplicateBranchElementsRule,
   ERBNoEmptyTagsRule,
-  ERBNoInterpolatedClassNamesRule,
   ERBNoExtraNewLineRule,
   ERBNoExtraWhitespaceRule,
-  ERBNoOutputControlFlowRule,
-  ERBNoThenInControlFlowRule,
-  ERBNoSilentTagInAttributeNameRule,
-  ERBNoTrailingWhitespaceRule,
-  ERBPreferImageTagHelperRule,
-  ERBRequireTrailingNewlineRule,
-  ERBRequireWhitespaceRule,
+  ERBNoInlineCaseConditionsRule,
+  ERBNoInstanceVariablesInPartialsRule,
+  ERBNoInterpolatedClassNamesRule,
   ERBNoJavascriptTagHelperRule,
+  ERBNoOutputControlFlowRule,
+  ERBNoOutputInAttributeNameRule,
+  ERBNoOutputInAttributePositionRule,
   ERBNoRawOutputInAttributeValueRule,
+  ERBNoSilentTagInAttributeNameRule,
   ERBNoStatementInScriptRule,
+  ERBNoThenInControlFlowRule,
+  ERBNoTrailingWhitespaceRule,
   ERBNoUnsafeJSAttributeRule,
   ERBNoUnsafeRawRule,
   ERBNoUnsafeScriptInterpolationRule,
+  ERBPreferImageTagHelperRule,
+  ERBRequireTrailingNewlineRule,
+  ERBRequireWhitespaceRule,
   ERBRightTrimRule,
-  ERBNoOutputInAttributePositionRule,
-  ERBNoOutputInAttributeNameRule,
-  ERBNoInstanceVariablesInPartialsRule,
   ERBStrictLocalsCommentSyntaxRule,
   ERBStrictLocalsRequiredRule,
 
-  HerbDisableCommentValidRuleNameRule,
-  HerbDisableCommentNoRedundantAllRule,
-  HerbDisableCommentNoDuplicateRulesRule,
-  HerbDisableCommentMissingRulesRule,
   HerbDisableCommentMalformedRule,
+  HerbDisableCommentMissingRulesRule,
+  HerbDisableCommentNoDuplicateRulesRule,
+  HerbDisableCommentNoRedundantAllRule,
   HerbDisableCommentUnnecessaryRule,
+  HerbDisableCommentValidRuleNameRule,
 
   HTMLAllowedScriptTypeRule,
   HTMLAnchorRequireHrefRule,
@@ -151,9 +156,10 @@ export const rules: RuleClass[] = [
   HTMLNoUnderscoresInAttributeNamesRule,
   HTMLRequireClosingTagsRule,
   HTMLTagNameLowercaseRule,
-  TurboPermanentRequireIdRule,
+
+  ParserNoErrorsRule,
 
   SVGTagNameCapitalizationRule,
 
-  ParserNoErrorsRule,
+  TurboPermanentRequireIdRule,
 ]

javascript/packages/linter/src/rules/actionview-no-silent-helper.ts

@@ -0,0 +1,58 @@
+import { ParserRule } from "../types.js"
+import { BaseRuleVisitor } from "./rule-utils.js"
+import { isERBOpenTagNode, isERBOutputNode } from "@herb-tools/core"
+
+import type { UnboundLintOffense, LintContext, FullRuleConfig } from "../types.js"
+import type { ParseResult, HTMLElementNode, ParserOptions } from "@herb-tools/core"
+
+class ActionViewNoSilentHelperVisitor extends BaseRuleVisitor {
+  visitHTMLElementNode(node: HTMLElementNode): void {
+    this.checkActionViewHelper(node)
+    super.visitHTMLElementNode(node)
+  }
+
+  private checkActionViewHelper(node: HTMLElementNode): void {
+    if (!node.element_source || node.element_source === "HTML") return
+    if (!isERBOpenTagNode(node.open_tag)) return
+    if (isERBOutputNode(node.open_tag)) return
+
+    const tagOpening = node.open_tag.tag_opening?.value
+
+    if (!tagOpening) return
+
+    const helperName = node.element_source.includes("#")
+      ? node.element_source.split("#").pop()
+      : node.element_source
+
+    this.addOffense(
+      `Avoid using \`${tagOpening} %>\` with \`${helperName}\`. Use \`<%= %>\` to ensure the helper's output is rendered.`,
+      node.open_tag.location,
+    )
+  }
+}
+
+export class ActionViewNoSilentHelperRule extends ParserRule {
+  static ruleName = "actionview-no-silent-helper"
+
+  get defaultConfig(): FullRuleConfig {
+    return {
+      enabled: true,
+      severity: "error"
+    }
+  }
+
+  get parserOptions(): Partial<ParserOptions> {
+    return {
+      track_whitespace: true,
+      action_view_helpers: true,
+    }
+  }
+
+  check(result: ParseResult, context?: Partial<LintContext>): UnboundLintOffense[] {
+    const visitor = new ActionViewNoSilentHelperVisitor(this.ruleName, context)
+
+    visitor.visit(result.value)
+
+    return visitor.offenses
+  }
+}