Tracing Function Execution

You can trace the arguments supplied to, and the result values produced by functions using C-c M-t v. CIDER will prompt you for the name of the function you want to trace, defaulting to the previous top-level definition.

Invoking C-c M-t v again for the same function will result in the function being untraced.

You can also use C-c M-t n to toggle tracing on and off for an entire namespace.

Since it’s easy to lose track of what you’ve traced, cider-list-traced displays all the currently traced vars and namespaces in a buffer, and cider-untrace-all clears every trace at once.

By default the trace output lands in the REPL, mixed in with everything else. cider-trace opens a dedicated *cider-trace* buffer instead: trace some functions, call them, and their calls and return values stream into that buffer live, indented to show the call nesting. Kill the buffer to stop streaming.

The cider-trace buffer with a nested call tree

Inside the buffer:

TAB (or a click) on a call line folds or unfolds the nested calls between it and its return, so you can collapse the noise and keep just the call and its result; F and U fold and unfold everything at once.
n and p move between calls.
. (or clicking a function’s name) jumps to its definition.

The same actions are available from the CIDER Trace menu.

All of these require a recent enough cider-nrepl.