erlang: exit-signal propagation + trap_exit (+11 tests)

lib/erlang/tests/eval.sx

@@ -502,6 +502,65 @@
       (= (len (er-proc-field (er-mk-pid 1) :monitored-by)) 0)))
   true)
 
+;; ── exit-signal propagation + trap_exit ────────────────────────
+(er-eval-test "process_flag default false"
+  (nm (ev "process_flag(trap_exit, true)")) "false")
+(er-eval-test "process_flag returns prev"
+  (nm (ev "process_flag(trap_exit, true), process_flag(trap_exit, false)"))
+  "true")
+
+;; Monitor fires on normal exit.
+(er-eval-test "monitor DOWN normal"
+  (nm (ev "P = spawn(fun () -> ok end), monitor(process, P), receive {'DOWN', _, process, _, R} -> R end"))
+  "normal")
+
+;; Monitor fires on abnormal exit.
+(er-eval-test "monitor DOWN abnormal"
+  (nm (ev "P = spawn(fun () -> exit(boom) end), monitor(process, P), receive {'DOWN', _, process, _, R} -> R end"))
+  "boom")
+
+;; Monitor's ref appears in DOWN message.
+(er-eval-test "monitor DOWN ref matches"
+  (nm (ev "P = spawn(fun () -> exit(bye) end), Ref = monitor(process, P), receive {'DOWN', Ref, process, _, _} -> ok_match end"))
+  "ok_match")
+
+;; Two monitors -> both fire.
+(er-eval-test "two monitors both fire"
+  (ev "P = spawn(fun () -> exit(crash) end), monitor(process, P), monitor(process, P), receive {'DOWN', _, _, _, _} -> ok end, receive {'DOWN', _, _, _, _} -> 2 end")
+  2)
+
+;; trap_exit + link + abnormal exit -> {'EXIT', From, Reason} message.
+(er-eval-test "trap_exit catches abnormal"
+  (nm (ev "process_flag(trap_exit, true), P = spawn(fun () -> exit(boom) end), link(P), receive {'EXIT', _, R} -> R end"))
+  "boom")
+
+;; trap_exit + link + normal exit -> {'EXIT', From, normal}.
+(er-eval-test "trap_exit catches normal"
+  (nm (ev "process_flag(trap_exit, true), P = spawn(fun () -> ok end), link(P), receive {'EXIT', _, R} -> R end"))
+  "normal")
+
+;; Cascade exit: A links B, B dies abnormally, A dies with same reason.
+(er-eval-test "cascade reason"
+  (do
+    (ev "A = spawn(fun () -> B = spawn(fun () -> exit(crash) end), link(B), receive forever -> ok end end), receive after 0 -> ok end")
+    (nm (er-proc-field (er-mk-pid 1) :exit-reason)))
+  "crash")
+
+;; Normal exit doesn't cascade (without trap_exit) — A's body returns
+;; "survived" via the `after` clause and A dies normally.
+(er-eval-test "normal exit no cascade"
+  (do
+    (ev "A = spawn(fun () -> B = spawn(fun () -> ok end), link(B), receive {'EXIT', _, _} -> got_exit after 50 -> survived end end), receive after 0 -> ok end")
+    (list
+      (nm (er-proc-field (er-mk-pid 1) :exit-reason))
+      (nm (er-proc-field (er-mk-pid 1) :exit-result))))
+  (list "normal" "survived"))
+
+;; Monitor without trap_exit: monitored proc abnormal doesn't kill the monitor.
+(er-eval-test "monitor doesn't cascade"
+  (nm (ev "P = spawn(fun () -> exit(boom) end), monitor(process, P), receive {'DOWN', _, _, _, _} -> alive end"))
+  "alive")
+
 (define
   er-eval-test-summary
   (str "eval " er-eval-test-pass "/" er-eval-test-count))