feat(style/oas2/oas3): autoclose xml empty tags in examples (#11055)

[adrianodpdiaz]

Motivation and Context

Fixes #11055

XML examples generated for schemas whose objects have only attributes (no child elements) were rendered as an open/close tag pair with an empty body (<c>\n</c>, <User id="123" name="bob">\n</User>, etc.), which is misleading — it looks like the element has content when it doesn't — and is not idiomatic XML. Idiomatic tooling renders these as self-closing tags (<c/>, <User id="123" name="bob"/>).

Now generated XML examples for elements with no child content (only attributes, or an empty array of attribute-only items) render as a self-closing tag instead of an empty tag pair with a stray blank line.

This affects both json-schema-2020-12-samples (OAS 3.1) and json-schema-5-samples (OAS 2.0/3.0) sample generators, so both were fixed identically to keep behavior consistent across spec versions, for all supported OAS versions: 2.0, 3.0.x, 3.1.x, and 3.2.x.

Changes

• Added a normalizeXMLContent() helper in both src/core/plugins/json-schema-2020-12-samples/fn/main.js and src/core/plugins/json-schema-5-samples/fn/index.js that recursively walks the sample object before it's handed to the xml package:
  • An empty array collapses to null.
  • An array whose items are all _attr-only objects (no real content) is merged into a single { _attr: {...} } object, so the xml package emits a self-closing tag with attributes instead of an empty tag with children.
  • All other arrays/objects are recursed into unchanged.
• createXMLExample() in both plugins now runs the generated sample through normalizeXMLContent() before passing it to XML(...).
• Updated existing Cypress and Jest tests/fixtures that asserted the old <tag>\n</tag> empty-tag-pair output to expect the new self-closing <tag/> output.

How Has This Been Tested?

• Updated and ran the existing regression tests covering this exact behavior:
  • test/e2e-cypress/e2e/bugs/4943.cy.js (XML example not rendered correctly with oneOf)
  • test/e2e-cypress/e2e/bugs/6627.cy.js (XML example when defined as an array)
  • test/e2e-cypress/e2e/features/oas3-xml.cy.js
  • test/unit/core/plugins/json-schema-2020-12-samples/fn.js
  • test/unit/core/plugins/json-schema-5-samples/fn/index.js
• npm run test:unit passes locally.
• Manually verified via npm run dev that XML examples for attribute-only objects and arrays of attribute-only objects now render as self-closing tags, while objects/arrays with real child content are unaffected.

Screenshots:

Before:

After:

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• [] Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

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• If yes to above: I have updated the documentation accordingly.

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