fix: [#1949] Implement implicit closing of elements per HTML spec by TrevorBurnham · Pull Request #2007 · capricorn86/happy-dom

TrevorBurnham · 2026-01-19T22:53:22Z

Fixes #1949

This PR fixes the HTML parser to correctly handle malformed HTML involving  elements. Per the HTML spec,  elements should be implicitly closed when certain block-level elements are encountered.

Problem

When parsing malformed HTML like testing with </div>new line, happy-dom produced:

<p>testing with <p>new line</p></p>

But browsers produce:

<p>testing with </p><p>new line</p>

Changes

`packages/happy-dom/src/config/HTMLElementConfig.ts`

Updated the  element configuration from anyDescendants to noForbiddenFirstLevelDescendants with a list of elements that should implicitly close :

p: {
    className: 'HTMLParagraphElement',
    contentModel: HTMLElementConfigContentModelEnum.noForbiddenFirstLevelDescendants,
    forbiddenDescendants: [
        'address', 'article', 'aside', 'blockquote', 'details', 'dialog',
        'div', 'dl', 'fieldset', 'figcaption', 'figure', 'footer', 'form',
        'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'header', 'hgroup', 'hr',
        'main', 'menu', 'nav', 'ol', 'p', 'pre', 'section', 'table', 'ul'
    ]
}

Implementation Details

The fix follows the WHATWG HTML Standard which specifies that a  element's end tag can be omitted (implicitly closed) when followed by these elements:

address, article, aside, blockquote, details, dialog, div, dl, fieldset, figcaption, figure, footer, form, h1, h2, h3, h4, h5, h6, header, hgroup, hr, main, menu, nav, ol, p, pre, search, section, table, ul

The implementation leverages the existing noForbiddenFirstLevelDescendants content model, which is already used by elements like <dd>, <dt>, and <option>.

Test Coverage

Original issue: stray </div> with nested 
Multiple  elements closing each other
Block-level elements closing  (div, h1, ul, table, section, hr, blockquote)
Inline elements NOT closing  (span, a, strong)
Nested structures
Stray end tags
Fragment parsing

…r HTML spec

capricorn86

Thank you for your contribution @TrevorBurnham! ⭐

1. Upgrade to [jQuery 4.0](https://blog.jquery.com/2026/01/17/jquery-4-0-0/). Two of the removed APIs are in use by fomantic, but there are [polyfills present](https://github.com/go-gitea/gitea/blob/a3a3e581aa387969ce6410ab54c4775e9023ec40/web_src/fomantic/build/components/dropdown.js#L15-L17) so it continues to work. 2. Remove manual naming of webpack chunks. I was running into below webpack error and I see no reason for this manual chunk naming which is prone to naming collisions. Also, the webpack build now shows all output assets. This change will result in longer asset filenames, but webpack should now be able to guarentee that the names are without collisions. ```` ERROR in SplitChunksPlugin Cache group "defaultVendors" conflicts with existing chunk. Both have the same name "--------" and existing chunk is not a parent of the selected modules. Use a different name for the cache group or make sure that the existing chunk is a parent (e. g. via dependOn). HINT: You can omit "name" to automatically create a name. BREAKING CHANGE: webpack < 5 used to allow to use an entrypoint as splitChunk. This is no longer allowed when the entrypoint is not a parent of the selected modules. Remove this entrypoint and add modules to cache group's 'test' instead. If you need modules to be evaluated on startup, add them to the existing entrypoints (make them arrays). See migration guide of more info. 3. Fix test issue related to `p > div` which is invalid as per HTML spec because `div` is not [phrasing content](https://html.spec.whatwg.org/multipage/dom.html#phrasing-content-2) and therefor can not be a descendant of `p`. This is related to capricorn86/happy-dom#2007. 4. Add webpack globals 5. Remove obsolete docs glob 6. fix security issue for `seroval` package 7. disable [vitest isolate](https://vitest.dev/config/isolate.html) for 30% faster JS tests, which are all pure.

…w flow content Fixes capricorn86#2052 ## Problem The caption element was incorrectly configured with contentModel: textOrComments, which only allowed text nodes and comments. Per the HTML spec, caption elements should contain flow content (inline and block elements), except table elements. This caused elements like , , , etc. to be incorrectly moved outside the caption during parsing. ## Changes ### packages/happy-dom/src/config/HTMLElementConfig.ts Updated caption element configuration to match the HTML spec and follow the same pattern as td/th elements: - Changed contentModel from textOrComments to noForbiddenFirstLevelDescendants - Added forbiddenDescendants: table structure elements (table, tbody, thead, tfoot, tr, td, th, col, colgroup) - Added permittedParents: ['table'] to ensure caption only appears in tables ### packages/happy-dom/test/html-parser/HTMLParser.malformedHTML.test.ts Added comprehensive test coverage for caption element content model: - Inline elements preservation (b, strong, em, span, a) - Nested inline elements - Block-level elements (p, div) - Table element prohibition - Content serialization - permittedParents validation (wrong parent, standalone, correct parent) ## Implementation Details This fix follows the same pattern as PR capricorn86#2007 for paragraph elements, using the existing noForbiddenFirstLevelDescendants content model. While this doesn't recursively check deeply nested table elements, it matches the existing codebase patterns and handles the vast majority of real-world cases. Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

…w flow content Fixes capricorn86#2052 ## Problem The caption element was incorrectly configured with contentModel: textOrComments, which only allowed text nodes and comments. Per the HTML spec, caption elements should contain flow content (inline and block elements), except table elements. This caused elements like , , , etc. to be incorrectly moved outside the caption during parsing. ## Changes ### packages/happy-dom/src/config/HTMLElementConfig.ts Updated caption element configuration to match the HTML spec and follow the same pattern as td/th elements: - Changed contentModel from textOrComments to noForbiddenFirstLevelDescendants - Added forbiddenDescendants: table structure elements (table, tbody, thead, tfoot, tr, td, th, col, colgroup) - Added permittedParents: ['table'] to ensure caption only appears in tables ### packages/happy-dom/test/html-parser/HTMLParser.malformedHTML.test.ts Added comprehensive test coverage for caption element content model: - Inline elements preservation (b, strong, em, span, a) - Nested inline elements - Block-level elements (p, div) - Table element prohibition - Content serialization - permittedParents validation (wrong parent, standalone, correct parent) ## Implementation Details This fix follows the same pattern as PR capricorn86#2007 for paragraph elements, using the existing noForbiddenFirstLevelDescendants content model. While this doesn't recursively check deeply nested table elements, it matches the existing codebase patterns and handles the vast majority of real-world cases.

…ent (#2058) Fixes #2052 ## Problem The caption element was incorrectly configured with contentModel: textOrComments, which only allowed text nodes and comments. Per the HTML spec, caption elements should contain flow content (inline and block elements), except table elements. This caused elements like , , , etc. to be incorrectly moved outside the caption during parsing. ## Changes ### packages/happy-dom/src/config/HTMLElementConfig.ts Updated caption element configuration to match the HTML spec and follow the same pattern as td/th elements: - Changed contentModel from textOrComments to noForbiddenFirstLevelDescendants - Added forbiddenDescendants: table structure elements (table, tbody, thead, tfoot, tr, td, th, col, colgroup) - Added permittedParents: ['table'] to ensure caption only appears in tables ### packages/happy-dom/test/html-parser/HTMLParser.malformedHTML.test.ts Added comprehensive test coverage for caption element content model: - Inline elements preservation (b, strong, em, span, a) - Nested inline elements - Block-level elements (p, div) - Table element prohibition - Content serialization - permittedParents validation (wrong parent, standalone, correct parent) ## Implementation Details This fix follows the same pattern as PR #2007 for paragraph elements, using the existing noForbiddenFirstLevelDescendants content model. While this doesn't recursively check deeply nested table elements, it matches the existing codebase patterns and handles the vast majority of real-world cases.

…w flow content (capricorn86#2058) Fixes capricorn86#2052 ## Problem The caption element was incorrectly configured with contentModel: textOrComments, which only allowed text nodes and comments. Per the HTML spec, caption elements should contain flow content (inline and block elements), except table elements. This caused elements like , , , etc. to be incorrectly moved outside the caption during parsing. ## Changes ### packages/happy-dom/src/config/HTMLElementConfig.ts Updated caption element configuration to match the HTML spec and follow the same pattern as td/th elements: - Changed contentModel from textOrComments to noForbiddenFirstLevelDescendants - Added forbiddenDescendants: table structure elements (table, tbody, thead, tfoot, tr, td, th, col, colgroup) - Added permittedParents: ['table'] to ensure caption only appears in tables ### packages/happy-dom/test/html-parser/HTMLParser.malformedHTML.test.ts Added comprehensive test coverage for caption element content model: - Inline elements preservation (b, strong, em, span, a) - Nested inline elements - Block-level elements (p, div) - Table element prohibition - Content serialization - permittedParents validation (wrong parent, standalone, correct parent) ## Implementation Details This fix follows the same pattern as PR capricorn86#2007 for paragraph elements, using the existing noForbiddenFirstLevelDescendants content model. While this doesn't recursively check deeply nested table elements, it matches the existing codebase patterns and handles the vast majority of real-world cases.

TrevorBurnham requested a review from capricorn86 as a code owner January 19, 2026 22:53

fix: [capricorn86#1949] Implement implicit closing of elements pe…

539c9fc

…r HTML spec

TrevorBurnham force-pushed the 1949-fix branch from 529567f to 539c9fc Compare January 19, 2026 23:36

capricorn86 approved these changes Jan 20, 2026

View reviewed changes

capricorn86 merged commit 63b8f3d into capricorn86:master Jan 20, 2026
3 checks passed

silverwind mentioned this pull request Jan 22, 2026

Update JS dependencies, adjust webpack config, misc fixes go-gitea/gitea#36431

Merged

atzzCokeK mentioned this pull request Feb 6, 2026

fix: [#2052] Correct caption element content model to allow flow content #2058

Merged

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fix: [#1949] Implement implicit closing of <p> elements per HTML spec#2007

fix: [#1949] Implement implicit closing of <p> elements per HTML spec#2007
capricorn86 merged 1 commit intocapricorn86:masterfrom
TrevorBurnham:1949-fix

TrevorBurnham commented Jan 19, 2026

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TrevorBurnham commented Jan 19, 2026

Problem

Changes

packages/happy-dom/src/config/HTMLElementConfig.ts

Implementation Details

Test Coverage

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`packages/happy-dom/src/config/HTMLElementConfig.ts`