Synthetic XML feed cases: five first errors a parser reports and one well-formed file that loses fields

The invented snippets and their first errors

This is a synthetic worked example with invented values, not a customer case or a supplier's file. Results marked computed were produced with Python's standard library on invented input. Each snippet is two or three lines. The messages below were produced by Python's built-in XML parser; other parsers word them differently, but the position of the first error is the useful part.

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case                         first error reported
unescaped ampersand           not well-formed (invalid token): line 2, column 18
  <item><name>Nuts & Bolts</name></item>
closing tag in a different case   mismatched tag: line 2, column 19
  <item><Name>Hinge</name></item>
control character (U+000B)    not well-formed (invalid token): line 2, column 17
text after the root element   junk after document element: line 4, column 0
bytes not valid in declared UTF-8   not well-formed (invalid token): line 2, column 15
  (declared utf-8; file bytes were Latin-1)

A well-formed file that still loses fields

The file below parses without error. The price lives in the Google namespace, and the name is a CDATA section whose text looks like markup and contains an ampersand. A text-matching importer looking for a plain price tag finds none and stores the name with its angle brackets treated as tags. A real parser with the namespace declared returns the price 4.20 GBP and the name Hinge <brass> & steel, as computed.

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<feed xmlns:g="http://base.google.com/ns/1.0">
<item><g:price>4.20 GBP</g:price>
<name><![CDATA[Hinge <brass> & steel]]></name></item>
</feed>

parser result: {g}price = '4.20 GBP'; name = 'Hinge <brass> & steel'

The assertions an importer test should make

Assert that the well-formed file stores both values exactly. Assert that each broken snippet is rejected as a whole, with the line and column of its first error in the message, and that the stored products are identical before and after the attempt. Assert that a document declaring an entity or an external resource is refused or left unexpanded, because Python's documentation warns that attacker-controlled XML can exhaust memory through entity expansion. These are authored expectations; no supplier's feed was read.

What this example does not show

It does not show how any supplier produces its XML, nor does it repair a broken file. A file that is not well-formed is the supplier's to correct; the specification treats it as a fatal error, and repairing it by text substitution can store wrong products.

Use it to specify a priced enquiry

If your importer fails one of these, the fixed job xml-supplier-feed-parse-errors-import is £295 for one importer path and one named supplier layout. Send a redacted sample and the exact parse message first, never real price lists, credentials or code. Prices are untested proposals, and payment follows the agreed checks and your sign-off. Nothing is booked or charged by an enquiry.