parse_xml function : text key added when it should not for single nodes

[ScriptToddler]

Hello,

Problem

There appears to be an inconsistency with text_key in parse_xml function

Whenever a chain of an "even" number of single child is present, the text key seems to be forcibly added even when it should not.
E.g. :

• <root><a>test</a></root> results in { "root": { "a": { "text": "test" } } } instead of expected { "root": { "a": "test" } }
  https://playground.vrl.dev/?state=eyJwcm9ncmFtIjoiLnhtbF9wYXJzZWQgPSBwYXJzZV94bWwhKC5tZXNzYWdlKSIsImV2ZW50Ijp7Im1lc3NhZ2UiOiI8cm9vdD48YT50ZXN0PC9hPjwvcm9vdD4ifSwiaXNfanNvbmwiOmZhbHNlLCJlcnJvciI6bnVsbH0%3D
• <root><a><a1>test</a1></a></root> results in expected { "root": { "a": { "a1": "test" } } }
  https://playground.vrl.dev/?state=eyJwcm9ncmFtIjoiLnhtbF9wYXJzZWQgPSBwYXJzZV94bWwhKC5tZXNzYWdlKSIsImV2ZW50Ijp7Im1lc3NhZ2UiOiI8cm9vdD48YT48YTE%2BdGVzdDwvYTE%2BPC9hPjwvcm9vdD4ifSwiaXNfanNvbmwiOmZhbHNlLCJlcnJvciI6bnVsbH0%3D
• <root><a><a1><a2>test</a2></a1></a></root> results in { "root": { "a": { "a1": { "a2": { "text": "test" } } } } } instead of expected { "root": { "a": { "a1": { "a2": "test" } } } }
  https://playground.vrl.dev/?state=eyJwcm9ncmFtIjoiLnhtbF9wYXJzZWQgPSBwYXJzZV94bWwhKC5tZXNzYWdlKSIsImV2ZW50Ijp7Im1lc3NhZ2UiOiI8cm9vdD48YT48YTE%2BPGEyPnRlc3Q8L2EyPjwvYTE%2BPC9hPjwvcm9vdD4ifSwiaXNfanNvbmwiOmZhbHNlLCJlcnJvciI6bnVsbH0%3D
• similarly, if you add a sibling to the <a> node, the <a1> node then is nested with a text key
  https://playground.vrl.dev/?state=eyJwcm9ncmFtIjoiLnhtbF9wYXJzZWQgPSBwYXJzZV94bWwhKC5tZXNzYWdlKSIsImV2ZW50Ijp7Im1lc3NhZ2UiOiI8cm9vdD48YT48YTE%2BdGVzdDwvYTE%2BPC9hPjxiPmZvbzwvYj48L3Jvb3Q%2BIn0sImlzX2pzb25sIjpmYWxzZSwiZXJyb3IiOm51bGx9

Investigation (might be mistaken)

I tried to investigate the issue and it seems to me the problem stems from the recurse implementation with single nodes, and precisely this line

vrl/src/stdlib/parse_xml.rs

Line 356 in e58ac80

Value::Object(recurse(node)),

When recursing the value of the node which would then incorrectly add the text key later on at this step (if I am not mistaken) :

vrl/src/stdlib/parse_xml.rs

Line 296 in e58ac80

for n in node.children().filter(|n| n.is_element() || n.is_text()) {

The problem seems to be fixed on my end if instead of the recurse, the process_node function is instead called on the node, with no regression seen so far.
I have proposed such a fix on a branch on my forked version of the project there https://github.com/vectordotdev/vrl/compare/main...ScriptToddler:vrl:fix/parse_xml_unique_child_text?expand=1 along with tests highlighting the issue.

I may be mistaken, in which case you may just discard what I said in this last part

Thank you,

[jszwedko]

Thanks for the thorough report @ScriptToddler ! I haven't reviewed the code changes, but the output for your example inputs definitely highlights the issue. We can review the code change if you want to open a PR.

[ScriptToddler]

Hi @jszwedko,
As suggested I opened a PR (#849) with my proposal, but then again not sure if it is the best way to fix the issue (but it does work for me with no regression seen thus far)