otel P1: span model + API (with-span, parent stack, ring buffer)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/host/tests/otel.sx

@@ -0,0 +1,74 @@
+;; lib/host/tests/otel.sx — P1: span model + API. A span dict
+;; {:trace :span :parent :name :t0 :t1 :attrs :events}; otel/with-span records
+;; t0/t1 and pushes/pops a dynamic parent stack so nesting builds the tree; a
+;; bounded ring buffer (record!/recent, cap, drop-oldest); current-span/current-trace.
+
+(define host-ot-pass 0)
+(define host-ot-fail 0)
+(define host-ot-fails (list))
+
+(define
+  host-ot-test
+  (fn
+    (name actual expected)
+    (if
+      (= actual expected)
+      (set! host-ot-pass (+ host-ot-pass 1))
+      (begin
+        (set! host-ot-fail (+ host-ot-fail 1))
+        (append! host-ot-fails {:name name :actual actual :expected expected})))))
+
+;; ── nested with-span builds the parent tree ─────────────────────────
+(otel/reset!)
+(otel/with-span "root" {}
+  (fn () (otel/with-span "child" {} (fn () 42))))
+
+(define host-ot-sp (otel/recent))
+(define host-ot-child (first host-ot-sp))   ;; inner span completes+records first
+(define host-ot-root (nth host-ot-sp 1))
+
+(host-ot-test "two spans recorded" (len host-ot-sp) 2)
+(host-ot-test "child name" (get host-ot-child :name) "child")
+(host-ot-test "root name" (get host-ot-root :name) "root")
+(host-ot-test "child parent is root span" (get host-ot-child :parent) (get host-ot-root :span))
+(host-ot-test "root has no parent" (get host-ot-root :parent) nil)
+(host-ot-test "same trace" (= (get host-ot-child :trace) (get host-ot-root :trace)) true)
+(host-ot-test "root t1 >= t0" (>= (get host-ot-root :t1) (get host-ot-root :t0)) true)
+(host-ot-test "root has attrs" (get host-ot-root :attrs) {})
+(host-ot-test "root has events list" (get host-ot-root :events) (list))
+
+;; ── attrs are carried through ───────────────────────────────────────
+(otel/reset!)
+(otel/with-span "req" {:http.method "GET" :http.route "/feed"} (fn () nil))
+(host-ot-test "attrs carried"
+  (get (get (first (otel/recent)) :attrs) :http.method) "GET")
+
+;; ── current-span / current-trace track the dynamic stack ────────────
+(otel/reset!)
+(host-ot-test "no current span outside" (otel/current-span) nil)
+(host-ot-test "no current trace outside" (otel/current-trace) nil)
+(otel/with-span "x" {}
+  (fn ()
+    (begin
+      (host-ot-test "current span set inside" (not (= (otel/current-span) nil)) true)
+      (host-ot-test "current trace set inside" (not (= (otel/current-trace) nil)) true)
+      nil)))
+(host-ot-test "no current span after" (otel/current-span) nil)
+
+;; ── ring buffer caps at N, drops oldest ─────────────────────────────
+(otel/reset!)
+(otel/set-cap! 3)
+(for-each (fn (i) (otel/record! {:span i :name "s"})) (list 1 2 3 4 5))
+(host-ot-test "ring capped at 3" (len (otel/recent)) 3)
+(host-ot-test "oldest dropped" (get (first (otel/recent)) :span) 3)
+(host-ot-test "newest kept" (get (last (otel/recent)) :span) 5)
+(otel/set-cap! 1000)
+
+(define
+  host-ot-tests-run!
+  (fn
+    ()
+    {:total (+ host-ot-pass host-ot-fail)
+     :passed host-ot-pass
+     :failed host-ot-fail
+     :fails host-ot-fails}))