Sayid nREPL API

Sayid ships an nREPL middleware (com.billpiel.sayid.nrepl-middleware/wrap-sayid) that exposes its tracing engine over the wire. The bundled Emacs client talks to Sayid exclusively through these ops, and any other editor or tool can do the same.

This document is the reference for that wire API.

Loading the middleware

With Leiningen, add Sayid as a plugin (it registers the middleware automatically):

{:user {:plugins [[mx.cider/sayid "0.2.0"]]}}

Or add the middleware explicitly when you start the server, e.g. with the Clojure CLI / nrepl.server:

(nrepl.server/start-server
 :handler (nrepl.server/default-handler #'com.billpiel.sayid.nrepl-middleware/wrap-sayid))

Conventions

Send a normal nREPL message with an "op" key naming one of the ops below, plus whatever parameters that op takes. Every op terminates the request with a :status of "done", so a synchronous client can block until it arrives.

Ops fall into two shapes:

• Command ops just do their work and reply with :status "done" (no value).
• Query ops reply with a :value, then :status "done".

Response values are already decoded - Sayid encodes them into plain bencode-friendly data (nested lists, strings and numbers) before they go on the wire, so by the time your nREPL client hands you a value it is ordinary data. Do not run it through a reader. A few encoding rules are worth knowing:

• keywords arrive as their bare name strings (:foo -> "foo"),
• booleans arrive as 1 / nil,
• anything Sayid can't represent structurally arrives as its printed string.

If an op throws, the response carries :status #{"error" "done"} along with :err (a stack trace) and :ex (the exception class), the same convention cider-nrepl uses, so the failure surfaces instead of hanging the client.

Several ops resolve "the thing at the cursor" server-side. They take the buffer source (the whole file as a string) plus a 1-based line and column, and Sayid parses the source to find the symbol there. This keeps editors from having to reimplement Clojure-aware symbol resolution.

Applying and managing traces

sayid-trace-fn-at-point

Apply a trace action to the function whose symbol is at the cursor.

param	meaning
action	one of add-outer, add-inner, enable, disable, remove
file	path of the buffer's file
line, column	1-based cursor position
source	the buffer's full text

Replies with the resolved qualified symbol (e.g. "my.ns/my-fn"), or nil when nothing resolves at that position.

sayid-trace-fn

Apply a trace action to an explicitly named function.

param	meaning
action	one of add-outer, add-inner, enable, disable, remove
fn-ns	the function's namespace
fn-name	the function's name

add-outer records calls to the function; add-inner additionally records every expression evaluated inside it. enable/disable flip an existing trace on and off; remove tears it down. Replies with :status "done".

sayid-trace-ns

Apply a trace action to a whole namespace.

param	meaning
action	one of enable, disable, remove
ns	the namespace name

Replies with :status "done".

sayid-all-traces

Apply a trace action to every trace at once.

param	meaning
action	one of enable, disable, remove

Replies with :status "done".

sayid-trace-ns-in-file

Trace the namespace declared in file. Param: file. Replies :status "done".

sayid-trace-ns-by-pattern

Trace every loaded namespace whose name matches a pattern.

param	meaning
ns-pattern	a namespace pattern, where * is a wildcard
ref-ns	a namespace to resolve the pattern relative to

Replies with :status "done".

sayid-trace-all-ns-in-dir

Recursively trace every namespace found under dir. Param: dir. Replies :status "done".

Inspecting recorded calls

sayid-get-workspace

Render the current workspace with the active view. Takes no params. Replies with the rendered tree as a [text text-properties query-args] triple, where text is the printable output, text-properties describes per-span coloring/metadata, and query-args is the printed query that produced it.

sayid-query

Run a query against the workspace. Param: query (a printed Clojure query form). Replies with the same [text properties query-args] triple as sayid-get-workspace.

sayid-query-form-at-point

Query the workspace for the calls that best match the cursor context. Params: file, line. Replies with a [text properties] pair.

sayid-query-by-id

Query for a recorded call by id, optionally with a modifier.

param	meaning
trace-id	the id of the recorded call
mod	a modifier string, e.g. "a" (ancestors), "d" (descendants), optionally with a depth

Replies with a [text properties query-args] triple.

sayid-query-by-fn

Like the above, but selects by function name. Params: fn-name, mod. Replies with a [text properties query-args] triple.

Acting on a recorded call

These operate on a single node in the rendered output, identified by trace-id (and path for nested values).

sayid-gen-instance-expr

Generate an expression that reproduces a recorded call, def-ing its arguments to $s/* vars along the way. Param: trace-id. Replies with the expression string (e.g. "(my.ns/my-fn $s/a $s/b)").

sayid-def-value

Def the value at path within the call trace-id to $s/*. Params: trace-id, path. Replies with a confirmation value.

sayid-pprint-value

Pretty-print the value at path within the call trace-id. Params: trace-id, path. Replies with the pretty-printed text.

Views

sayid-set-view

Select a named view for subsequent rendering. Param: view-name. Replies :status "done".

sayid-toggle-view

Toggle between the default and the verbose view. Takes no params. Replies with the new state.

sayid-get-views

List the registered view names. Takes no params. Replies with the view names.

Workspace lifecycle

sayid-clear-log

Clear the recorded calls but keep the traces in place. Takes no params. Replies :status "done".

sayid-reset-workspace

Remove all traces and clear the recorded calls. Takes no params. Replies :status "done".

Introspection

sayid-version

Replies with the Sayid version string (e.g. "0.2.0").

sayid-get-trace-count

Replies with the number of traces in the workspace.

sayid-get-enabled-trace-count

Replies with the number of currently enabled traces.

sayid-get-meta-at-point

Resolve the symbol at the cursor and report its metadata. Params: source, file, line.

sayid-find-all-ns-roots

Replies with the distinct source roots of the loaded namespaces (e.g. ["src" "test"]), handy for offering a directory to scan.

sayid-show-traced

Render the list of what's currently traced. Optional param: ns (limit to one namespace). Replies with the rendered tree.