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HTML Parser fails if you have the same attribute twice

See original GitHub issue

Describe the bug

It seems that if you have the same attribute twice, the HTML parser to fail. (Tested it with class=, data-a= and x=. It fails for all of them.)

Reproduction

(Repro on Stackblitz.)

<!DOCTYPE html>
<div class="a" class="b"></div>

Output:

[vite] Internal server error: Unable to parse {"file":"/index.html","line":2,"column":16}
1  |  <!DOCTYPE html>
2  |  <div class="a" class="b"></div>
   |                 ^
3  |  
      at traverseHtml (/home/projects/vitejs-vite-wv2wbb/node_modules/vite/dist/node/chunks/dep-e0fe87f8.js:21240:15)
      at async devHtmlHook (/home/projects/vitejs-vite-wv2wbb/node_modules/vite/dist/node/chunks/dep-e0fe87f8.js:57001:5)
      at async applyHtmlTransforms (/home/projects/vitejs-vite-wv2wbb/node_modules/vite/dist/node/chunks/dep-e0fe87f8.js:21550:21)
      at async viteIndexHtmlMiddleware (/home/projects/vitejs-vite-wv2wbb/node_modules/vite/dist/node/chunks/dep-e0fe87f8.js:57065:28)

System Info

Stackblitz.

Used Package Manager

npm

Logs

No response

Validations

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Check that there isn’t already an issue that reports the same bug to avoid creating a duplicate.
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The provided reproduction is a minimal reproducible example of the bug.

Issue Analytics

State:
Created 2 years ago
Comments:11 (7 by maintainers)

Top GitHub Comments

5reactions

yyx990803commented, Dec 13, 2021

https://html.spec.whatwg.org/multipage/syntax.html#attributes-2

Quote:

There must never be two or more attributes on the same start tag whose names are an ASCII case-insensitive match for each other.

If your markup contains duplicated attributes, you should fix it. If your tool is generating duplicated attributes, it’s a bug in that tool and you should ask that tool to fix it.

That said, browsers do silently allow duplicated attributes, so Vite should not break the build because of it. But still.

4reactions

surmacommented, Dec 8, 2021

If the same attribute is specified multiple times, the first one wins.

I am running into this because I’m using vite to optimize and bundle the output from 11ty. Lots my HTML is programmatically generated and happens to have duplicate attributes.