Add with-logging-to-port to unstable.

original commit: 8d96133681a1302c9395485b969049c9a072d552

collects/unstable/logging.rkt

@@ -0,0 +1,38 @@
+#lang racket/base
+
+(require racket/contract)
+
+(define (with-logging-to-port port level proc)
+  (let* ([logger    (make-logger #f (current-logger))]
+         [receiver  (make-log-receiver logger level)]
+         [stop-chan (make-channel)]
+         [t (thread (lambda ()
+                      (define (output-event l)
+                        (displayln (vector-ref l 1) ; actual message
+                                   port))
+                      (define (clear-events)
+                        (let ([l (sync/timeout 0 receiver)])
+                          (when l ; still something to read
+                            (output-event l)
+                            (clear-events))))
+                      (let loop ()
+                        (let ([l (sync receiver stop-chan)])
+                          (cond [(eq? l 'stop)
+                                 ;; we received all the events we were supposed
+                                 ;; to get, read them all (w/o waiting), then
+                                 ;; stop
+                                 (clear-events)]
+                                [else ; keep going
+                                 (output-event l)
+                                 (loop)])))))])
+    (begin0
+        (parameterize ([current-logger logger])
+          (proc))
+      (channel-put stop-chan 'stop) ; stop the receiver thread
+      (thread-wait t))))
+
+(provide/contract [with-logging-to-port
+                   (-> output-port?
+                       (or/c 'fatal 'error 'warning 'info 'debug)
+                       (-> any)
+                       any)])