fix: attr-value-no-duplication (#1667)

Author: coliff

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "htmlhint",
-  "version": "1.6.1",
+  "version": "1.6.2",
   "description": "The Static Code Analysis Tool for your HTML",
   "keywords": [
     "html",

package.json

@@ -20,8 +20,12 @@ export default {
         // Skip content, media, and style attributes entirely
         if (
           attr.name.toLowerCase() === 'content' ||
+          attr.name.toLowerCase() === 'd' ||
           attr.name.toLowerCase() === 'media' ||
-          attr.name.toLowerCase() === 'style'
+          attr.name.toLowerCase() === 'sizes' ||
+          attr.name.toLowerCase() === 'src' ||
+          attr.name.toLowerCase() === 'style' ||
+          attr.name.toLowerCase().startsWith('on') // Skip all event handlers (onclick, onchange, etc.)
         ) {
           continue
         }

src/core/rules/attr-value-no-duplication.ts

@@ -98,4 +98,25 @@ describe(`Rules: ${ruleId}`, () => {
     const messages = HTMLHint.verify(code, ruleOptions)
     expect(messages.length).toBe(0)
   })
+
+  it('Script src attribute should be skipped entirely', () => {
+    const code =
+      '<script src="data:text/javascript,window.analytics = window.analytics || function() { (window.analytics.q = window.analytics.q || []).push(arguments) }"></script>'
+    const messages = HTMLHint.verify(code, ruleOptions)
+    expect(messages.length).toBe(0)
+  })
+
+  it('Sizes attribute should be skipped entirely', () => {
+    const code =
+      '<source type="" sizes="(min-width: 1rem) 1vw, (min-width: 2rem) 2vw" srcset="">'
+    const messages = HTMLHint.verify(code, ruleOptions)
+    expect(messages.length).toBe(0)
+  })
+
+  it('Event handler attributes should be skipped entirely', () => {
+    const code =
+      "<button onclick=\"trackEvent('click'); validateForm(); trackEvent('click');\">Submit</button>"
+    const messages = HTMLHint.verify(code, ruleOptions)
+    expect(messages.length).toBe(0)
+  })
 })

test/rules/attr-value-no-duplication.spec.js

@@ -5,6 +5,10 @@ description: The release notes for HTMLHint, see what's changed with each new ve
 
 import { Badge } from '@astrojs/starlight/components'
 
+## 1.6.2 _(2025-06-18)_
+
+- <Badge text="Fix" size="small" variant="danger" /> Improve [`attr-value-no-duplication`](/rules/attr-value-no-duplication/) logic
+
 ## 1.6.1 _(2025-06-17)_
 
 - <Badge text="Fix" size="small" variant="danger" /> Improve SARIF report formatting

website/src/content/docs/changelog.mdx

@@ -14,7 +14,7 @@ hero:
       variant: minimal
 banner:
   content: |
-    v1.6.1 is now available! Check the <a href="/changelog/">changelog</a> to see what's new.
+    v1.6.2 is now available! Check the <a href="/changelog/">changelog</a> to see what's new.
 tableOfContents: false
 lastUpdated: false
 editUrl: false

website/src/content/docs/index.mdx

@@ -31,6 +31,22 @@ Level: <Badge text="Error" variant="danger" />
 <div class="btn btn-primary btn-large">Button</div>
 ```
 
+```html
+<source type="" sizes="(min-width: 1rem) 1vw, (min-width: 2rem) 2vw" srcset="">
+```
+
+## Excluded attributes
+
+The following attributes are excluded from this rule and will not trigger errors even if they contain duplicate values:
+
+- `content` - Common for meta tags that may contain duplicate keywords
+- `d` - Used in SVG path data which may contain repetitive pattern data
+- `media` - Used for media queries which have special parsing rules
+- `on*` - All event handlers (onclick, onkeydown, etc.) that may contain legitimate duplicate JavaScript operations
+- `sizes` - Used in responsive images with complex viewport conditions
+- `src` - URLs and data URIs that might legitimately contain repeated patterns
+- `style` - Inline CSS which has its own syntax and may contain duplicate property names
+
 ### The following patterns are considered rule violations:
 
 ```html
@@ -42,7 +58,7 @@ Level: <Badge text="Error" variant="danger" />
 ```
 
 ```html
-<div class="btn    primary   btn">Button</div>
+<div class="btn  primary btn">Button</div>
 ```
 
 ## Why does this rule exist?

website/src/content/docs/rules/attr-value-no-duplication.mdx

@@ -23,10 +23,9 @@ This rule prevents the use of HTML tags that have been deprecated and are consid
 
 ### Obsolete tags include:
 
-- `applet`, `acronym`, `bgsound`, `dir`, `frame`, `frameset`, `noframes`
-- `isindex`, `keygen`, `listing`, `menuitem`, `nextid`, `noembed`
-- `plaintext`, `rb`, `rtc`, `strike`, `xmp`, `basefont`, `big`
-- `blink`, `center`, `font`, `marquee`, `multicol`, `nobr`, `spacer`, `tt`
+`acronym`, `applet`, `basefont`, `bgsound`, `big`, `blink`, `center`, `dir`, `font`, `frame`, `frameset`,
+`isindex`, `keygen`, `listing`, `marquee`, `menuitem`, `multicol`, `nextid`, `nobr`, `noembed`, `noframes`,
+`plaintext`, `rb`, `rtc`, `spacer`, `strike`, `tt`, `xmp`
 
 ### The following patterns are **not** considered rule violations