app

{"record":{"id":"f63480fdc91a65f1","repo":"leptos-rs/leptos","slug":"missing-head-element","errorCode":null,"errorMessage":"missing element","messagePattern":"missing element","errorType":"panic","errorClass":null,"httpStatus":null,"severity":"error","filePath":"meta/src/lib.rs","lineNumber":122,"sourceCode":" pub(crate) cursor: Arc>>,\n}\n\nimpl MetaContext {\n /// Creates an empty [`MetaContext`].\n pub fn new() -> Self {\n Default::default()\n }\n}\n\npub(crate) const HEAD_MARKER_COMMENT: &str = \"HEAD\";\n/// Return value of [`Node::node_type`] for a comment.\n/// https://developer.mozilla.org/en-US/docs/Web/API/Node/nodeType#node.comment_node\nconst COMMENT_NODE: u16 = 8;\n\nimpl Default for MetaContext {\n fn default() -> Self {\n let build_cursor: fn() -> SendWrapper = || {\n let head = document().head().expect(\"missing element\");\n let mut cursor = None;\n let mut child = head.first_child();\n while let Some(this_child) = child {\n if this_child.node_type() == COMMENT_NODE\n && this_child.text_content().as_deref()\n == Some(HEAD_MARKER_COMMENT)\n {\n cursor = Some(this_child);\n break;\n }\n child = this_child.next_sibling();\n }\n SendWrapper::new(Cursor::new(\n cursor\n .expect(\n \"no leptos_meta HEAD marker comment found. Did you \\\n include the component in the of \\\n your server-rendered app?\",","sourceCodeStart":104,"sourceCodeEnd":140,"githubUrl":"https://github.com/leptos-rs/leptos/blob/32d20f6c9d517451d77beb68d88c7716823dac41/meta/src/lib.rs#L104-L140","documentation":"MetaContext::default builds a cursor positioned at the head-marker comment inside so metadata can be injected during hydration. It unwraps document().head(), panicking with \"missing element\" if the current document has no . The library assumes a well-formed HTML document exists when leptos_meta runs on the client.","triggerScenarios":"Constructing MetaContext::default() (directly or via leptos_meta's provider/hydration path) when document().head() returns None — e.g. a document with no section, or running in an environment with an incomplete DOM.","commonSituations":"Custom SSR shells that omit , streaming responses where the head chunk was already consumed/removed, or test DOMs built without head elements.","solutions":["Ensure the document being hydrated contains a element (valid HTML shell).","Create MetaContext only in browser environments where a full document exists.","In tests, build the DOM with a containing the marker comment if you exercise meta hydration.","Do not strip from the served markup before hydration."],"exampleFix":"\n...\n\n\napp\n...","handlingStrategy":"validation","validationCode":"if document().head().is_none() {\n console_error!(\"document has no ; leptos_meta unavailable\");\n return;\n}","typeGuard":"fn has_head() -> bool {\n document().head().is_some()\n}","tryCatchPattern":null,"preventionTips":["Include (with the marker when hydrating meta) in every served document.","Create MetaContext only after DOM readiness in a real browser.","Don't strip the head chunk from streamed SSR output."],"tags":["leptos","meta","dom","hydration"],"backgroundTag":"missing-head-element","analyzedSha":"32d20f6c9d517451d77beb68d88c7716823dac41","analyzedAt":"2026-09-01T18:55:42.580Z","contentChangedAt":null,"schemaVersion":2},"datasetVersion":"2026-09-09T01:17:15.007Z"}