Non-deterministic root attribute ordering during XML encoding

[JoshBashed]

Summary

XMLCoder currently does not guarantee deterministic ordering of root XML attributes during encoding. This makes encoded XML output unstable across runs and complicates snapshot testing or byte-for-byte comparisons.

Note

This issue was generated using AI tooling.

Problem

When doing encoding tests for XML, I need to disable inclusion of rootAttributes for testing because their ordering is not deterministic.

For example, the same encoded object may produce different attribute ordering between runs:

<Package xmlns="..." xmlns:uap="..." IgnorableNamespaces="uap" />

and:

<Package IgnorableNamespaces="uap" xmlns:uap="..." xmlns="..." />

Even though these are semantically equivalent XML documents, the resulting byte output differs, which causes snapshot or equality-based tests to fail.

Currently, I need to use a workaround similar to:

static func encodeXMLData(
  _ manifest: XMLData,
  disablingRootAttributesForTesting: Bool = false
)

Expected Behavior

Encoded XML attribute ordering should be deterministic across runs.

Possible solutions could include:

• Preserving insertion order
• Sorting attributes before serialization
• Providing a configurable ordering strategy

Impact

This affects:

• Snapshot testing
• Byte-for-byte output comparisons
• Reproducible build workflows
• Stable XML fixture generation

It also forces downstream consumers to omit root attributes during tests, reducing test coverage of the final encoded XML output.

Additional Context

I understand XML attribute order is not semantically meaningful according to the XML specification. However, deterministic output is still important for testing and reproducibility purposes.