[Bug] Unable to measure code action items size in shadow DOM

Open

#5,195 opened on Jan 19, 2026 0 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 2/5
Estimated time: 1-3 hours
Newbie friendliness: 48/100

Issue type: Bug
Clarity: Mostly clear
Activity status: Stale
Tech stack: typescript
Domain: frontend, web-dev

Research direction

Start at src/vs/platform/actionWidget/browser/actionList.ts around line 335, using the linked Monaco playground reproduction to inspect code-action sizing inside a shadow DOM. Verify the ownerDocument lookup and compare the result with the non-shadow-DOM example. Done means the code-action widget measures correctly in the shadow-DOM reproduction without changing the existing behavior outside it.

Written by the indexing model from the issue text.

Description

Reproducible in vscode.dev or in VS Code Desktop?

Not reproducible in vscode.dev or VS Code Desktop

Reproducible in the monaco editor playground?

Not reproducible in the monaco editor playground

Monaco Editor Playground Link

https://microsoft.github.io/monaco-editor/playground.html?source=v0.56.0-dev-20260119#XQAAAAL1BgAAAAAAAABBqQkHQ5Njdzmwfsp38WgHbUZ87XjZjkxRizxr48ySgyi1PHCopus5pzZ7nawcrO5v4hy0XAl_3CXCteK4RAZFtaNdMXqkOZoPPiDAs-gkmIquc5pyjUumlWqnSkiNMTdQQ9v7R00eaMZQ_GTKVhQI0QLmk5jCpaBGvl4WNCwDIeFNu3TRBJ9ZDLqbRGReSGaQF5akvXu_kDrWww1uceBcVlB4ckZ_GdXAuGbhfmC1nKin0Yk2_Cc6tlWHBx7g6-cRxihzVjpes_w8zht0dzFnSi0yMyx3fC3TiAAYzAhodLvOMgYoZB-KJCT0gGfV2BukQG2IM-ak3_ZG2ut7-TacSgRyrvWomod61_c6e9bulYaVA6UaTXqZW_jXTRca2fz4NKrHQR6Tk-tMNAnCrsK1kJFAfcRUPGQUTm0kKSlMTsubZFLEcl_N9ridjdXBuyb8lEcFRMM71pPUZu9i107wa0LEztttazrdr6qAtzojY9ZZXconTY4ETYVvbbJMYmNzopjwWL_IcT5ZR1oYQc3Uv_v0iZSa6Ibf8lUY6jyigzQTSRfLBb6H73O2U90ueJRO4Zdm814XIa8ZKRb19kDi44RSUNj3EUDVc0rvNBEfUVOAjZa_bZrQPo7iu16pQfimnSkP3L6QsOmOdo0ut8rJSNoDbLJt-N9waxQ1oCIURYLBAn9-ca-ZsxGNY_BROVGrb3zxWrYe48A_AsZfnn1WASjuKcx-nMa5RnZNfpa2VYK7LOEkudE44T0jqsxQMlRapcIxrXQvHxs_Davh9f_reM6DA9XVMQMiBQShGUrotfr5WPPFMfwJOGLBGUErztGejV3NtWl99KTH5Fd5MknUKIqzKODpDouZQcApc1yCh83ZBdQR1kiY4lbWZQLYkEyWKQivrFRxG9_h4UvvNtRgIkprQXR2e9QJWWDE9WhzeqVxJAURk5CEqalwaeKiOFbg-IsZnk4SrHDUTW1oTdOYj0kn5SG-QcwSp3gzIdkX_CLq3zHjtSSqT0EX4SOmLJz9KxvBE80Kwb7NwsrwMoVM5t7Lpj6FmFdkXuSGyeP0put-iSw22Vj2SzWZYRy4ZOGaLNAYol0E9KF0BkduYCe-T2CniFVvDS5X7mlayYZVnGXImpU0hSVB8gt8AokjZddJDzC0U7m6PzDUgQiK3WmN1nYdpgAF-7EgFSamPXciU5Agl7h329Cop__3hT6c

Monaco Editor Playground Code

<div>Hello World</div>

Reproduction Steps

Press Ctrl + . to show code actions.

Actual (Problematic) Behavior

Expected Behavior

What it looks like without a shadow dom wrapper.

Link: https://microsoft.github.io/monaco-editor/playground.html?source=v0.56.0-dev-20260119#XQAAAAJfAwAAAAAAAABBqQkHQ5NjdMjwa-jY7SIQ9S7DNlzs5W-mwj0fe1ZCDRFc9ws9XQE0SJE1jc2VKxhaLFIw9vEWSxW3yscw4KS44Or1jwBJ-cPayCQY4iC3FrkE9a7POHp3QG-jDr4FdR5dywU6Cn5I9YaMjRMGQGA__k81gg9A2vBYtwcfkNcLjY1fAijAVzYoU7vvchF3wxVKn7IjFPRRmquBv0vVAskdYhJy1kwQEDMdwHjMb9B1kusQL9jSRgpdEUS6qHoehhHZ0sHHvjSzizTsRby6fDUYR0h3qT57SAT6xmWbhWCjKVIHoUCkPoChhUfvR9gLlhQB7FmRqq_aCvvZly5YuOVQ7Ocvr5sXYc4Baqv5wza_Z8HUVKGktoy-_oAF43mCim2nGz1VCj5ozQLrPFYsPwl9s4QhZPBw-EcVxUBhC__mj1jDP61tAuHmHgLfEnh9Ame0xDWGBd1Jg-1x3wXmGBvmADKZlYCwFW0U3dliCuPkLPF5-m_8byag98Dacg2cqn2BJcz-JBreCOwFwOJexxoCUgzHR_NvqxI-VJyVH7Tta_3oVmXN4pxgVNnTF3e0Xr7hisnTuIkayM-DX_-6YJp_egdsF4quptEQpIRom1NMATEzDrPVl0OqNe_xzYO22EH2sryybez9EG-H_zZ4ZQA

Additional Context

Change .ownerDocument to .getRootNode() fixes this issue.

https://github.com/microsoft/vscode/blob/6b921dda5c679c6ca1928a4505567c533ede72f9/src/vs/platform/actionWidget/browser/actionList.ts#L335

Dominant language: JavaScript
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Merged PRs (30d): 1

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