Implement getElementById on Document and DocumentFragment#618
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The polyfill gave ParentNode querySelector and querySelectorAll, but the
NonElementParentNode.getElementById lookup was missing, so
document.getElementById(id) threw "document.getElementById is not a function"
inside a remote environment. Host code is typically type-checked against
lib.dom, which does declare the method, so the gap was invisible to every
static check and surfaced only at runtime in the browser.
Return the first element in tree order whose id attribute matches. Match that
attribute literally rather than delegating to querySelector('#' + id): an id is
a string, not a selector, and the selector tokenizer has no escape handling, so
an id containing '.', ':', '[', or whitespace would parse as a different
selector.
Co-Authored-By: Claude <noreply@anthropic.com>
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closing in favour of #620 |
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Problem
@remote-dom/polyfillgivesParentNodebothquerySelector()andquerySelectorAll(), but theNonElementParentNode.getElementById()lookup is missing. Inside a remote environment,document.getElementById(id)throws:This is a nasty failure mode for host code, because remote code is normally type-checked against
lib.dom, which does declaregetElementById. So the call is type-clean, passes every static check, and only blows up at runtime in the sandbox. We hit exactly this in Shopify's admin: a script handler in a remote view looked up an element by id to call an imperative method on it, typechecked green, and threw as soon as the handler ran.Fix
Implement
getElementById()onDocumentandDocumentFragment(the twoNonElementParentNodehosts per the DOM spec — deliberately not onElement), delegating to a shared helper inshared.ts. This mirrors how the existingquerySelector/querySelectorAlldelegate toselectors.ts.The helper returns the first element in tree order whose
idattribute matches, walking the existingCHILD/NEXTlinks.It matches the
idattribute literally rather than delegating toquerySelector('#' + id). An id is a string, not a selector, and the selector tokenizer inselectors.tshas no escape handling — so an id containing.,:,[, or whitespace would parse as a different selector entirely and silently return the wrong element (or nothing).getElementById('a.b')must find<div id="a.b">, not an<a>with classb.