Regression test for #4159

src/core/sources/debug_sources.ml

@@ -58,4 +58,28 @@ let _ =
     ~descr:
       "A source that errors during its initialization phase, used for testing \
        and debugging." ~flags:[`Experimental] ~return_t [] (fun _ ->
-      (new fail_init :> Source.source))
+      new fail_init)
+
+class is_ready s =
+  object (self)
+    inherit Source.operator ~name:"is_ready" [s]
+    method seek_source = (self :> Source.source)
+    method fallible = true
+    method private can_generate_frame = true
+    method self_sync = (`Static, None)
+    method remaining = 0
+    method abort_track = ()
+    method generate_frame = if s#is_ready then s#get_frame else self#empty_frame
+  end
+
+let _ =
+  let return_t = Lang.frame_t (Lang.univ_t ()) Frame.Fields.empty in
+  Lang.add_operator ~base:Modules.debug "is_ready" ~category:`Input
+    ~descr:
+      "A source that always produces an empty frame when the underlying source \
+       is not ready, used for testing and debugging."
+    ~flags:[`Experimental] ~return_t
+    [("", Lang.source_t return_t, None, None)]
+    (fun p ->
+      let s = Lang.to_source (List.assoc "" p) in
+      new is_ready s)

tests/regression/GH4159.liq

@@ -0,0 +1,5 @@
+s = debug.is_ready(sine(duration=0.2))
+
+s = source.dynamic(track_sensitive=false, {s})
+
+output.dummy(fallible=true, on_stop=test.pass, s)

tests/regression/dune.inc

@@ -735,6 +735,22 @@
   (:run_test ../run_test.exe))
  (action (run %{run_test} GH4144.liq liquidsoap %{test_liq} GH4144.liq)))
 
+(rule
+ (alias citest)
+ (package liquidsoap)
+ (deps
+  GH4159.liq
+  ../media/all_media_files
+  ../../src/bin/liquidsoap.exe
+  ../streams/file1.png
+  ../streams/file1.mp3
+  ./theora-test.mp4
+  (package liquidsoap)
+  (source_tree ../../src/libs)
+  (:test_liq ../test.liq)
+  (:run_test ../run_test.exe))
+ (action (run %{run_test} GH4159.liq liquidsoap %{test_liq} GH4159.liq)))
+
 (rule
  (alias citest)
  (package liquidsoap)