Fix delay initial conditions again. (#4296)

src/core/operators/delay.ml

@@ -29,6 +29,7 @@ class delay ~initial (source : source) delay =
   object (self)
     inherit operator ~name:"delay" [source]
     val mutable last_track = if initial then Unix.time () else 0.
+    val mutable first_track = true
     method fallible = true
     method remaining = source#remaining
 
@@ -44,7 +45,9 @@ class delay ~initial (source : source) delay =
     method private generate_frame =
       let frame = source#get_frame in
       match self#split_frame frame with
-        | buf, Some _ when last_track = 0. && Frame.position buf = 0 -> frame
+        | buf, Some _ when first_track && Frame.position buf = 0 ->
+            first_track <- false;
+            frame
         | buf, Some _ ->
             last_track <- Unix.time ();
             buf

tests/regression/GH4281-2.liq

@@ -1,31 +1,23 @@
-d = sine()
+d = sequence([sine(duration=3.), sine(duration=3.)])
 d = metadata.map(update=false, (fun (_) -> [("title", "delay")]), d)
 
-f = sine()
+f = sequence([sine(duration=3.), sine(duration=3.)])
 f = metadata.map(update=false, (fun (_) -> [("title", "fallback")]), f)
 
-s = fallback([delay(initial=true, 60.0, d), f])
+s = fallback([delay(initial=true, 1., d), f])
 
-is_done = ref(false)
+meta = ref([])
 
 s.on_metadata(
   fun (m) ->
     begin
+      meta := [...meta(), m["title"]]
       if
-        not is_done()
+        meta() == ["fallback", "delay", "fallback", "delay"]
       then
-        if
-          m["title"] == "fallback"
-        then
-          begin
-            is_done := true
-            test.pass()
-          end
-        else
-          test.fail()
-        end
+        test.pass()
       end
     end
 )
 
-output.dummy(s)
+output.dummy(fallible=true, s)

tests/regression/GH4281.liq

@@ -1,31 +1,23 @@
-d = sine()
+d = sequence([sine(duration=3.), sine(duration=3.)])
 d = metadata.map(update=false, (fun (_) -> [("title", "delay")]), d)
 
-f = sine()
+f = sequence([sine(duration=3.), sine(duration=3.)])
 f = metadata.map(update=false, (fun (_) -> [("title", "fallback")]), f)
 
-s = fallback([delay(60.0, d), f])
+s = fallback([delay(1., d), f])
 
-is_done = ref(false)
+meta = ref([])
 
 s.on_metadata(
   fun (m) ->
     begin
+      meta := [...meta(), m["title"]]
       if
-        not is_done()
+        meta() == ["delay", "fallback", "delay", "fallback"]
       then
-        if
-          m["title"] == "delay"
-        then
-          begin
-            is_done := true
-            test.pass()
-          end
-        else
-          test.fail()
-        end
+        test.pass()
       end
     end
 )
 
-output.dummy(s)
+output.dummy(fallible=true, s)