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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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30
host/chez/source-registry.ss
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@ -145,10 +145,11 @@
;; TCO-truncated non-tail spine.
;; Each frame maps to "ns/name (file:line)" when registered, else its bare name.
;; #f when neither source yields a frame (the caller then prints just the location).
(define (jolt-backtrace-string v)
;; The tail-frame history ring rendered as a backtrace, or #f when tracing is off /
;; empty. A mapped frame is kept; else drop plumbing (same rule as the continuation
;; path) so the two sources read consistently.
(define (jolt-history-backtrace)
(let* ((hist (jolt-trace-snapshot))
;; a mapped frame is always kept; else drop plumbing (same rule as the
;; continuation path) so the two backtrace sources read consistently
(recs (let loop ((ns hist) (acc '()))
(if (null? ns)
(reverse acc)
@ -156,12 +157,23 @@
(loop (cdr ns)
(if (or src (not (srcreg-plumbing-name? nm)))
(cons (cons nm src) acc) acc)))))))
(if (pair? recs)
(jolt-render-recs recs)
(let ((k (jolt-error-continuation v)))
(and k
(let ((recs (jolt-frame-records k)))
(and (pair? recs) (jolt-render-recs recs))))))))
(and (pair? recs) (jolt-render-recs recs))))
(define (jolt-backtrace-string v)
(or (jolt-history-backtrace)
(let ((k (jolt-error-continuation v)))
(and k
(let ((recs (jolt-frame-records k)))
(and (pair? recs) (jolt-render-recs recs)))))))
;; Exposed for the REPL / nREPL error paths, which catch errors themselves instead
;; of going through the uncaught reporter. Returns the " trace:\n<frames>" block
;; from the tail-frame HISTORY only — the live continuation in a REPL is just the
;; REPL's own machinery — or nil when tracing is off (so a caller can when-let).
(def-var! "jolt.host" "backtrace-string"
(lambda ()
(let ((bt (jolt-history-backtrace)))
(if bt (string-append " trace:\n" bt) jolt-nil))))
;; Render an uncaught jolt throw (any value, not just a Chez condition) to a port:
;; an ex-info shows its message + ex-data (+ a host cause); anything else is