Dev meeting – debugging XQuery and XSLT – 8th January 2021

In the dev meeting today, we talked about debugging XQuery.

XQuery is a query language (primarily) for XML (in very loose terms, it’s like SQL for XML). Reece is the developer of an IntelliJ IDEA plugin that supports development of XQuery in IDEA. The latest changes he’s made to it allow it to be used for debugging XQuery in MarkLogic.

In IDEA, after installing his plugin, you need to set up an XQuery Run/Debug configuration for the MarkLogic server you are debugging. Then, you can run an XQuery file from within IDEA against MarkLogic, and it will display the output in the MarkLogic console.

Using standard IDEA breakpoints, you can add a breakpoint to an XQuery expression. Then, you can debug, which shows the stack frame, and the current variables and their values.

There is some complexity in working out the stack frames for eval expressions, which dynamically execute XQuery code in strings. Inigo expressed the opinion that this was generally a bad idea anyway.

At the moment, it’s not possible to debug into X-Ray XQuery tests, but Reece is doing further work to make it possible to run X-Ray tests easily from IDEA, which would also include work to make X-Ray tests debuggable.

Reece is also working on debug support for Saxon, which will support debugging in XQuery and in XSLT via Saxon.