raco test: add --heartbeat flag

Useful when running many tests in parallel to keep track of a test
that is running especially long (and maybe stuck).

pkgs/compiler-pkgs/compiler-lib/compiler/commands/test.rkt

@@ -31,6 +31,7 @@
 (define table? #f)
 (define fresh-user? #f)
 (define empty-input? #f)
+(define heartbeat-secs #f)
 (define ignore-stderr-patterns null)
 
 (define jobs 0) ; 0 mean "default"
@@ -490,6 +491,24 @@
                              (format " ~s" (format "~a" a)))))
             (flush-output))
           id)))
+     (define heartbeat-sema (make-semaphore))
+     (define heartbeat-t
+       (and heartbeat-secs
+            (thread (lambda ()
+                      (let loop ()
+                        (unless (sync/timeout heartbeat-secs heartbeat-sema)
+                          (call-with-semaphore
+                           ids-lock
+                           (lambda ()
+                             (printf "raco test: ~a[still on ~s]\n"
+                                     (if (jobs . <= . 1)
+                                         ""
+                                         (format "~a " id))
+                                     (let ([m (normalize-module-path p)])
+                                       (if (and (pair? mod) (eq? 'submod (car mod)))
+                                           (list* 'submod m (cddr mod))
+                                           m)))))
+                          (loop)))))))
      (begin0
       (dynamic-require* mod 0
                         #:id (if (jobs . <= . 1)
@@ -501,6 +520,9 @@
                         #:responsible responsible
                         #:lock-name lock-name
                         #:random? random?)
+      (when heartbeat-t
+        (semaphore-post heartbeat-sema)
+        (sync heartbeat-t))
       (call-with-semaphore
        ids-lock
        (lambda ()
@@ -972,6 +994,9 @@
  [("--quiet" "-q")
   "Suppress `raco test: ...' message"
   (set! quiet? #t)]
+ [("--heartbeat")
+  "Periodically report that a test is still running"
+  (set! heartbeat-secs 5)]
  [("--table" "-t")
   "Print a summary table"
   (set! table? #t)]

pkgs/racket-pkgs/racket-doc/scribblings/raco/test.scrbl

@@ -120,24 +120,28 @@ The @exec{raco test} command accepts several flags:
       example) does @emph{not} change for each test process.}
 
  @item{@DFlag{empty-stdin}
-       --- provide an empty stdin to each test program.}
+       --- Provide an empty stdin to each test program.}
 
  @item{@Flag{Q} or @DFlag{quiet-program}
-       --- suppresses output from each test program.}
+       --- Suppresses output from each test program.}
 
  @item{@Flag{e} or @DFlag{check-stderr}
-       --- count any stderr output as a test failure.}
+       --- Count any stderr output as a test failure.}
 
  @item{@DPFlag{ignore-stderr} @nonterm{pattern}
-       --- don't count stderr output as a test failure if it matches
+       --- Don't count stderr output as a test failure if it matches
        @nonterm{pattern}.  This flag can be used multiple times, and
        stderr output is treated as success as long as it matches any
        one @nonterm{pattern}.}
 
  @item{@Flag{q} or @DFlag{quiet}
-       --- suppresses output of progress information, responsible
+       --- Suppresses output of progress information, responsible
        parties, and varying output (see @secref["test-responsible"]).}
 
+ @item{@DFlag{heartbeat}
+       --- Periodically report that a test is still running after
+       the test has been running at least 5 seconds.}
+
  @item{@DFlag{table} or @Flag{t}
        --- Print a summary table after all tests. If a test uses
        @racketmodname[rackunit], or if a test at least uses