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Trace by default in REPL-driven development

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A repl or nREPL session now turns tail-frame tracing on, so an uncaught error in
evaluated/reloaded code shows a tail-frame backtrace with no JOLT_TRACE set. The
REPL and nREPL catch errors themselves rather than going through the uncaught
reporter, so they now print the history backtrace via a new jolt.host/backtrace-
string (history-only — the live continuation in a REPL is just REPL machinery).

Because the recording is baked in at compile time, only code compiled while a
session is live is traced; reload a namespace to trace already-loaded code.
JOLT_TRACE=1 still forces it on for a whole run (a plain -M:run traces its own
load); JOLT_TRACE=0 forces it off even in a session.

No seed change — jolt.main/jolt.nrepl are runtime-loaded and compile-eval.ss /
source-registry.ss are host files.
This commit is contained in:
Yogthos 2026-07-04 15:23:17 -04:00
parent a3e2365217
commit 7167af4830
6 changed files with 89 additions and 23 deletions
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7
jolt-core/jolt/main.clj
View file

@ -147,6 +147,9 @@
;; loaded — same context a run gets, so (require '[some.lib]) works in the REPL.
(try (apply-project! (deps/resolve-project (project-dir)))
(catch :default _ nil))
;; REPL-driven development: trace by default so an uncaught error in evaluated
;; code shows a tail-frame backtrace, no JOLT_TRACE needed (JOLT_TRACE=0 opts out).
(jolt.host/enable-trace!)
(println (str ";; jolt " (version) " repl — :repl/quit or ^D to exit"))
(loop []
(let [form (repl-read-form)]
@ -160,7 +163,9 @@
(catch :default e
(println "error:" (or (ex-message e)
(try ((resolve 'jolt.host/condition-message) e) (catch :default _ nil))
(pr-str e)))))
(pr-str e)))
(when-let [bt (jolt.host/backtrace-string)]
(print bt))))
(recur)))))))
;; A deps.edn :tasks entry: a string is a shell command; a map is {:main-opts …}.

10
jolt-core/jolt/nrepl.clj
View file

@ -188,7 +188,10 @@
(try (when (and ns-str (not (str/blank? ns-str)) (find-ns (symbol ns-str)))
(in-ns (symbol ns-str)))
(reset! result (load-string code))
(catch :default e (reset! err (err-msg e)))))]
(catch :default e
(reset! err (str (err-msg e)
(when-let [bt (jolt.host/backtrace-string)]
(str "\n" bt)))))))]
{:value (when (nil? @err) (pr-str @result))
:out out
:ns (str (ns-name *ns*))
@ -277,6 +280,11 @@
no-op."
([port] (start port nil))
([port middleware]
;; An nREPL session is REPL-driven development: trace by default so an uncaught
;; error in code evaluated over the connection shows a tail-frame backtrace, with
;; no JOLT_TRACE needed. Covers both `--nrepl-server` and an app that starts its
;; own server under `-M:run` (reload a namespace to trace already-loaded code).
(jolt.host/enable-trace!)
(let [handler (build-handler (resolve-middleware (or middleware [])))
fd (listen-socket port) ; throws on bind/listen failure
stopped (atom false)]