dbus XML parser fails to parse XML documents with namespace extensions about haskell-dbus

[rblaze]

The parser only looks for specific attributes and ignores all others, so it shouldn't be bothered by namespaces. Maybe xml-conduit requires some additional setup to handle this kind of document.

Can you make a minimal spec that makes the parser fail with namespaces? A fix would be even better, but I'll look into it when I have time.

[crogers1]

Hey rblaze, I work with tsirakisn. A spec trimmed down and "examplified" from the code we're working with is described below, borrowing from telepathy for enum:

<!DOCTYPE node PUBLIC "-//freedesktop//DTD D-BUS Object Introspection 1.0//EN" "http://www.freedesktop.org/standards/dbus/1.0/introspect.dtd">
<node xmlns:tp="http://telepathy.freedesktop.org/wiki/DbusSpec#extensions-v0" name="/">
  <tp:enum name="EX_ENUM" type="s">
    <tp:enumvalue suffix="EX1" value="ex1"/>
  </tp:enum>
  <interface name="my.example.interface">
    <method name="cool_method">
      <arg type="s" name="argin" direction="in"/>
    </method>
  </interface>
</node>

putting this through parseXML fails. Dropping the enum block, and thus leaving only basic interface, method, and arg tags will allow parseXML to succeed.

Thanks for your time in looking at this.

[rblaze]

It has nothing to do with namespaces, at least in the test case.

Here the parser expects that node's child is either a child node or interface definition. enum is neither, so parsing fails.

Could you try replacing X.many with X.many' and see if it works for you?

[tsirakisn]

@rblaze appreciate the quick turnaround! I gave that change a try and it does indeed parse test document above but still fails to parse my files. Going to dig into this a bit and report back. Thanks again.

[tsirakisn]

Okay, after replacing a few more X.many's with the alternative, my files are parsing. I was initially concerned that ignoring the tags would introduce undesired behavior, but it seems that my binaries are behaving correctly somehow. I think those results are good enough to close this issue, at least for my purposes. Thanks for your help!

[rblaze]

I can patch the parser to make it skip over unknown elements if you send me the full XML file. It already skips unknown attributes and can skip unknown nodes as well.

Just to point out, the Introspection module is not required to operate the library. It is a codegen to produce a service stub. You can write one yourself and save the trouble.

[tsirakisn]

I can patch the parser to make it skip over unknown elements if you send me the full XML file

I have it patched on my end, which is good enough for my purposes. Whether you decide to add formal support is up to you.

Just to point out, the Introspection module is not required to operate the library. It is a codegen to produce a service stub. You can write one yourself and save the trouble.

Ack, good to know

[rblaze]

I'm closing this issue for now. Feel free to send a pull request if you want this fixed on my side.

[tsirakisn]

@rblaze I can submit it if you'd like the fix to be mainlined. I didn't think you'd want it to be.

[rblaze]

Why not? It is possible other people will run into the same problem.

[rblaze]

Could you also add a test case covering your changes? It will prevent breakages in the future, given this code path won't be widely used.

[tsirakisn]

Agreed, I just didn't know if this change in particular was the route you wanted to go for a formal fix (and I am definitely no Haskell expert). I have no problem submitting with a test case 👍