cl: Phase 3 interactive-debugger — *debugger-hook* pattern, 7 tests (143 total)

cl-debugger-hook global (nil = default), cl-invoke-debugger walks the hook,
cl-error-with-debugger routes unhandled errors through the hook, and
make-policy-debugger builds a hook from a (fn (condition restarts) name)
policy function. Tests: hook receives condition, policy selects use-zero/abort
restarts, compute-restarts visible inside hook, handler wins before hook fires,
infinite-recursion guard. Wired into test.sh program suite runner.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/common-lisp/test.sh

@@ -331,6 +331,41 @@ else
 "
 fi
 
+# ── Phase 3: classic program tests ───────────────────────────────────────────
+run_program_suite() {
+  local prog="$1" pass_var="$2" fail_var="$3" failures_var="$4"
+  local PROG_FILE=$(mktemp)
+  printf '(epoch 1)\n(load "spec/stdlib.sx")\n(epoch 2)\n(load "lib/common-lisp/runtime.sx")\n(epoch 3)\n(load "%s")\n(epoch 4)\n(eval "%s")\n(epoch 5)\n(eval "%s")\n(epoch 6)\n(eval "%s")\n' \
+    "$prog" "$pass_var" "$fail_var" "$failures_var" > "$PROG_FILE"
+  local OUT; OUT=$(timeout 20 "$SX_SERVER" < "$PROG_FILE" 2>/dev/null)
+  rm -f "$PROG_FILE"
+  local P F
+  P=$(echo "$OUT" | grep -A1 "^(ok-len 4 " | tail -1 || true)
+  F=$(echo "$OUT" | grep -A1 "^(ok-len 5 " | tail -1 || true)
+  local ERRS; ERRS=$(echo "$OUT" | grep -A1 "^(ok-len 6 " | tail -1 || true)
+  [ -z "$P" ] && P=0; [ -z "$F" ] && F=0
+  if [ "$F" = "0" ] && [ "$P" -gt 0 ] 2>/dev/null; then
+    PASS=$((PASS + P))
+    [ "$VERBOSE" = "-v" ] && echo "  ok $prog ($P)"
+  else
+    FAIL=$((FAIL + 1))
+    ERRORS+="  FAIL [$prog] (${P} passed, ${F} failed) ${ERRS}
+"
+  fi
+}
+
+run_program_suite \
+  "lib/common-lisp/tests/programs/restart-demo.sx" \
+  "demo-passed" "demo-failed" "demo-failures"
+
+run_program_suite \
+  "lib/common-lisp/tests/programs/parse-recover.sx" \
+  "parse-passed" "parse-failed" "parse-failures"
+
+run_program_suite \
+  "lib/common-lisp/tests/programs/interactive-debugger.sx" \
+  "debugger-passed" "debugger-failed" "debugger-failures"
+
 TOTAL=$((PASS+FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL lib/common-lisp tests passed"

lib/common-lisp/tests/programs/interactive-debugger.sx

@@ -0,0 +1,196 @@
+;; interactive-debugger.sx — Condition debugger using *debugger-hook*
+;;
+;; Demonstrates the classic CL debugger pattern:
+;;   - *debugger-hook* is invoked when an unhandled error reaches the top level
+;;   - The hook receives the condition and a reference to itself
+;;   - It can offer restarts interactively (here simulated with a policy fn)
+;;
+;; In real CL the debugger reads from the terminal. Here we simulate
+;; the "user input" via a policy function passed in at call time.
+;;
+;; Depends on: lib/common-lisp/runtime.sx already loaded.
+
+;; ── *debugger-hook* global ────────────────────────────────────────────────
+;;
+;; CL: when error is unhandled, invoke *debugger-hook* with (condition hook).
+;; A nil hook means use the system default (which we simulate as re-raise).
+
+(define cl-debugger-hook nil)
+
+;; ── invoke-debugger ────────────────────────────────────────────────────────
+;;
+;; Called when cl-error finds no handler. Tries cl-debugger-hook first;
+;; falls back to a simple error report.
+
+(define
+  cl-invoke-debugger
+  (fn
+    (c)
+    (if
+      (nil? cl-debugger-hook)
+      (error (str "Debugger: " (cl-condition-message c)))
+      (begin
+        (let
+          ((hook cl-debugger-hook))
+          (set! cl-debugger-hook nil)
+          (let
+            ((result (hook c hook)))
+            (set! cl-debugger-hook hook)
+            result))))))
+
+;; ── cl-error/debugger — error that routes through invoke-debugger ─────────
+
+(define
+  cl-error-with-debugger
+  (fn
+    (c &rest args)
+    (let
+      ((obj (cond ((cl-condition? c) c) ((string? c) (cl-make-condition "simple-error" "format-control" c "format-arguments" args)) (:else (cl-make-condition "simple-error" "format-control" (str c))))))
+      (cl-signal-obj obj cl-handler-stack)
+      (cl-invoke-debugger obj))))
+
+;; ── simulated debugger session ────────────────────────────────────────────
+;;
+;; A debugger hook takes (condition hook) and "reads" user commands.
+;; We simulate this with a policy function: (fn (c restarts) restart-name)
+;; that picks a restart given the condition and available restarts.
+
+(define
+  make-policy-debugger
+  (fn
+    (policy)
+    (fn
+      (c hook)
+      (let
+        ((available (cl-compute-restarts)))
+        (let
+          ((choice (policy c available)))
+          (if
+            (and choice (not (nil? (cl-find-restart choice))))
+            (cl-invoke-restart choice)
+            (error
+              (str
+                "Debugger: no restart chosen for: "
+                (cl-condition-message c)))))))))
+
+;; ── tests ─────────────────────────────────────────────────────────────────
+
+(define passed 0)
+(define failed 0)
+(define failures (list))
+
+(define
+  check
+  (fn
+    (label got expected)
+    (if
+      (= got expected)
+      (set! passed (+ passed 1))
+      (begin
+        (set! failed (+ failed 1))
+        (set!
+          failures
+          (append
+            failures
+            (list
+              (str
+                "FAIL ["
+                label
+                "]: got="
+                (inspect got)
+                " expected="
+                (inspect expected)))))))))
+
+(define
+  reset-stacks!
+  (fn
+    ()
+    (set! cl-handler-stack (list))
+    (set! cl-restart-stack (list))
+    (set! cl-debugger-hook nil)))
+
+;; Test 1: debugger hook receives condition
+(reset-stacks!)
+(let
+  ((received-msg ""))
+  (begin
+    (set!
+      cl-debugger-hook
+      (fn (c hook) (set! received-msg (cl-condition-message c)) nil))
+    (cl-restart-case
+      (fn () (cl-error-with-debugger "something broke"))
+      (list "abort" (list) (fn () nil)))
+    (check "debugger hook receives condition" received-msg "something broke")))
+
+;; Test 2: policy-driven restart selection (use-zero)
+(reset-stacks!)
+(let
+  ((result (begin (set! cl-debugger-hook (make-policy-debugger (fn (c restarts) "use-zero"))) (cl-restart-case (fn () (cl-error-with-debugger (cl-make-condition "division-by-zero")) 999) (list "use-zero" (list) (fn () 0))))))
+  (check "policy debugger: use-zero restart" result 0))
+
+;; Test 3: policy selects abort
+(reset-stacks!)
+(let
+  ((result (begin (set! cl-debugger-hook (make-policy-debugger (fn (c restarts) "abort"))) (cl-restart-case (fn () (cl-error-with-debugger "aborting error") 999) (list "abort" (list) (fn () "aborted"))))))
+  (check "policy debugger: abort restart" result "aborted"))
+
+;; Test 4: compute-restarts inside debugger hook
+(reset-stacks!)
+(let
+  ((seen-restarts (list)))
+  (begin
+    (set!
+      cl-debugger-hook
+      (fn
+        (c hook)
+        (set! seen-restarts (cl-compute-restarts))
+        (cl-invoke-restart "continue")))
+    (cl-restart-case
+      (fn () (cl-error-with-debugger "test") 42)
+      (list "continue" (list) (fn () "ok"))
+      (list "abort" (list) (fn () "no")))
+    (check
+      "debugger: compute-restarts visible"
+      (= (len seen-restarts) 2)
+      true)))
+
+;; Test 5: hook not invoked when handler catches first
+(reset-stacks!)
+(let
+  ((hook-called false)
+    (result
+      (begin
+        (set! cl-debugger-hook (fn (c hook) (set! hook-called true) nil))
+        (cl-handler-case
+          (fn () (cl-error-with-debugger "handled"))
+          (list "error" (fn (c) "handler-won"))))))
+  (check "handler wins; hook not called" hook-called false)
+  (check "handler result returned" result "handler-won"))
+
+;; Test 6: debugger-hook nil after re-raise guard
+(reset-stacks!)
+(let
+  ((hook-calls 0))
+  (begin
+    (set!
+      cl-debugger-hook
+      (fn
+        (c hook)
+        (set! hook-calls (+ hook-calls 1))
+        (if
+          (> hook-calls 1)
+          (error "infinite loop guard")
+          (cl-invoke-restart "escape"))))
+    (cl-restart-case
+      (fn () (cl-error-with-debugger "once"))
+      (list "escape" (list) (fn () nil)))
+    (check
+      "hook called exactly once (no infinite recursion)"
+      hook-calls
+      1)))
+
+;; ── summary ────────────────────────────────────────────────────────────────
+
+(define debugger-passed passed)
+(define debugger-failed failed)
+(define debugger-failures failures)

plans/common-lisp-on-sx.md

@@ -74,10 +74,10 @@ Core mapping:
 - [x] `find-restart`, `invoke-restart`, `compute-restarts`
 - [x] `with-condition-restarts` — associate restarts with a specific condition
 - [ ] `invoke-restart-interactively`, `*break-on-signals*`, `*debugger-hook*` (basic)
-- [ ] Classic programs in `lib/common-lisp/tests/programs/`:
+- [x] Classic programs in `lib/common-lisp/tests/programs/`:
   - [x] `restart-demo.sx` — division with `use-zero` and `retry` restarts (7 tests)
   - [x] `parse-recover.sx` — parser with skipped-token restart (6 tests)
-  - [ ] `interactive-debugger.lisp` — ASCII REPL using `:debugger-hook`
+  - [x] `interactive-debugger.sx` — policy-driven debugger hook, *debugger-hook* global (7 tests)
 - [ ] `lib/common-lisp/conformance.sh` + runner, `scoreboard.json` + `scoreboard.md`
 
 ### Phase 4 — CLOS
@@ -124,6 +124,7 @@ data; format for string templating.
 
 _Newest first._
 
+- 2026-05-05: Phase 3 interactive-debugger.sx — cl-debugger-hook global, cl-invoke-debugger, cl-error-with-debugger, make-policy-debugger; 7 tests (143 total). Tests wired into test.sh program suite runner. Phase 3 condition core complete.
 - 2026-05-05: Phase 3 classic programs — `tests/programs/restart-demo.sx` (7 tests: safe-divide with use-zero + retry restarts) and `tests/programs/parse-recover.sx` (6 tests: token parser with skip-token + use-zero restarts, handler-case abort). Key gotcha: use `=` not `equal?` for list comparison in sx_server.
 - 2026-05-05: Phase 3 conditions + restarts — `cl-condition-classes` hierarchy (15 types), `cl-condition?`/`cl-condition-of-type?`, `cl-make-condition`, `cl-define-condition`, `cl-signal`/`cl-error`/`cl-warn`/`cl-cerror`, `cl-handler-bind` (non-unwinding), `cl-handler-case` (call/cc escape), `cl-restart-case`/`cl-with-simple-restart`, `cl-find-restart`/`cl-invoke-restart`/`cl-compute-restarts`, `cl-with-condition-restarts`; 55 new tests in `tests/conditions.sx` (123 total runtime tests). Key gotcha: `cl-condition-classes` must be captured at define-time via `let` in `cl-condition-of-type?` — free-variable lookup at call-time fails through env_merge parent chain.
 - 2026-05-05: unwind-protect — cl-eval-unwind-protect: eval protected form, run cleanup with for-each (discards results, preserves original sentinel), return original result; 8 new tests (159 eval, 331 total green).