[spec-api]: XMLParser does not decode `
` by default

[JiaqiZhang-Dev]

Describe the bug

Context

• Go's nightly build pipeline failed with this test XMLModelWithTextValue_Put.
• The root cause is Go's encoding/xml encodes \n in xml as 
, The dev version of @typespec/spec-api (0.1.0-dev.3) switched its XML parser from xml2js to fast-xml-parser in this pr. XMLParser() with default options leaves 
 as a literal string, so spector's comparison of the request body against the expected value fails.

Fix

• The XMLParser may need to add those config processEntities: true, htmlEntities: true, and trimValues: false to support 
 characters. https://github.com/microsoft/typespec/blob/main/packages/spec-api/src/request-validations.ts#L67

Reproduction

// repro.mjs
// Demonstrates that fast-xml-parser does not decode 
 (numeric char ref for \n)
// by default, which causes Spector XML payload comparison to fail when the Go SDK
// encodes newlines in chardata fields as 
 (valid per XML spec, encoding/xml default).

import { XMLParser } from "fast-xml-parser";

// Go's encoding/xml serializes a chardata field containing "\n  text\n"
// as the following wire XML:
const wireXml = "<root>&#xA;  This is some text.&#xA;</root>";

// Expected value (what the TypeSpec spec / Go test expects):
const expected = "\n  This is some text.\n";

const defaultResult  = new XMLParser().parse(wireXml).root;
const fixedResult    = new XMLParser({ processEntities: true, htmlEntities: true, trimValues: false })
                         .parse(wireXml).root;

console.log("wire XML  :", wireXml);
console.log("expected  :", JSON.stringify(expected));
console.log("default   :", JSON.stringify(defaultResult),  defaultResult  === expected ? "✅" : "❌ MISMATCH");
console.log("with fix  :", JSON.stringify(fixedResult),    fixedResult    === expected ? "✅" : "❌ MISMATCH");

Expected output:

wire XML  : <root>&#xA;  This is some text.&#xA;</root>
expected  : "\n  This is some text.\n"
default   : "&#xA;  This is some text.&#xA;" ❌ MISMATCH
with fix  : "\n  This is some text.\n" ✅

Checklist

• Follow our Code of Conduct
• Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion.
• The provided reproduction is a minimal reproducible example of the bug.

[JiaqiZhang-Dev]

solved by removing new lines: https://github.com/Azure/autorest.go/pull/1917/changes