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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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25
host/chez/compile-eval.ss
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@ -110,13 +110,24 @@
;; older seed during the first re-mint pass.
(let ((scv (var-deref "jolt.backend-scheme" "set-var-cache!")))
(when (procedure? scv) (scv #t)))
;; JOLT_TRACE opts into tail-frame history: the emitter prepends a frame-recording
;; push to every runtime-compiled fn, and the ring buffer is allocated for this
;; thread. Off by default, so a normal run emits and pays exactly as before.
(when (getenv "JOLT_TRACE")
(let ((stf (var-deref "jolt.backend-scheme" "set-trace-frames!")))
(when (procedure? stf) (stf #t)))
(jolt-trace-enable!))
;; Tail-frame history. Turning it on makes the emitter add a per-fn history push to
;; every fn compiled AFTERWARD, and allocates this thread's ring. Suppressed when
;; JOLT_TRACE is explicitly falsey, so JOLT_TRACE=0 disables it even in dev mode.
(define (jolt-enable-trace!)
(let ((e (getenv "JOLT_TRACE")))
(unless (and e (member e '("0" "false" "no")))
(let ((stf (var-deref "jolt.backend-scheme" "set-trace-frames!")))
(when (procedure? stf) (stf #t)))
(jolt-trace-enable!))))
;; Exposed so the REPL / nREPL entrypoints (jolt.main, jolt.nrepl) can turn tracing
;; on for REPL-driven development without the user setting JOLT_TRACE. Because the
;; push is baked in at compile time, only code compiled after this call is traced —
;; which is exactly the code you eval / reload in a live session.
(def-var! "jolt.host" "enable-trace!" jolt-enable-trace!)
;; Explicit opt-in for a whole run (JOLT_TRACE=1): enable at load, BEFORE any app
;; namespace is compiled, so a plain `-M:run` traces the app's own code too.
(let ((e (getenv "JOLT_TRACE")))
(when (and e (not (member e '("0" "false" "no" "")))) (jolt-enable-trace!)))
;; (with-meta sym m) -> sym, else x — an (ns ^:no-doc name …) yields the name with
;; reader metadata as a with-meta form; strip it to read the bare ns symbol.