Fix mutual recursion between autocue and replaygain metadata resolvers.

CHANGES.md

@@ -16,8 +16,10 @@ Changed:
   is also passed. Add a configuration key to disable this mechanism.
   (#4235, #2676)
 
-Changed:
+Fixed:
 
+- Fixed request resolution loop when enabling both `autcue`
+  and `replaygain` metadata resolvers (#4245, fixed in #4246)
 - Convert all ICY (icecast) metadata from `input.http` to `utf8`.
 
 ---

src/core/builtins/builtins_resolvers.ml

@@ -21,6 +21,13 @@
  *****************************************************************************)
 
 let decoder_metadata = Lang.add_module ~base:Modules.decoder "metadata"
+let reentrant_decoders = ref []
+
+let _ =
+  Lang.add_builtin ~base:decoder_metadata "reentrant" ~category:`Liquidsoap
+    ~descr:"Return the list of reentrant decoders." []
+    (Lang.list_t Lang.string_t) (fun _ ->
+      Lang.list (List.map Lang.string !reentrant_decoders))
 
 let _ =
   let resolver_t =
@@ -47,6 +54,13 @@ let _ =
         Some
           "Decode files that have the file extensions in this list. Accept any \
            file if `null`." );
+      ( "reentrant",
+        Lang.bool_t,
+        Some (Lang.bool false),
+        Some
+          "Set to `true` to indicate that the decoder needs to resolve a \
+           request. Such decoders need to be mutually exclusive to avoid \
+           request resolution loops!" );
       ("", Lang.string_t, None, Some "Format/resolver's name.");
       ( "",
         resolver_t,
@@ -70,6 +84,7 @@ let _ =
           (List.assoc "file_extensions" p)
       in
       let log = Log.make ["decoder"; "metadata"] in
+      let reentrant = Lang.to_bool (List.assoc "reentrant" p) in
       let priority = Lang.to_int_getter (List.assoc "priority" p) in
       let resolver ~metadata ~extension ~mime fname =
         if
@@ -88,6 +103,7 @@ let _ =
       in
       Plug.register Request.mresolvers format ~doc:""
         { Request.priority; resolver };
+      if reentrant then reentrant_decoders := format :: !reentrant_decoders;
       Lang.unit)
 
 let add_playlist_parser ~format name (parser : Playlist_parser.parser) =

src/libs/autocue.liq

@@ -775,7 +775,7 @@ def autocue.internal.implementation(
             fade_out_type?: string,
             fade_out_curve?: float,
             start_next?: float,
-            extra_metadata?: [(string * string)]
+            extra_metadata?: [(string*string)]
           }
         )
       end
@@ -823,7 +823,10 @@ def file.autocue.metadata(~request_metadata, uri) =
       )
     end
 
-  r = request.create(excluded_metadata_resolvers=["autocue"], uri)
+  r =
+    request.create(
+      excluded_metadata_resolvers=decoder.metadata.reentrant(), uri
+    )
 
   if
     not request.resolve(r)
@@ -1059,6 +1062,7 @@ def enable_autocue_metadata() =
     mime_types=mime_types,
     file_extensions=file_extensions,
     priority=settings.autocue.metadata.priority,
+    reentrant=true,
     "autocue",
     autocue_metadata
   )

src/libs/replaygain.liq

@@ -76,7 +76,7 @@ def replaces file.replaygain(~id=null(), ~compute=true, ~ratio=50., file_name) =
   id = string.id.default(default="file.replaygain", id)
   file_name_quoted = string.quote(file_name)
 
-  _metadata = file.metadata(exclude=["replaygain_track_gain"], file_name)
+  _metadata = file.metadata(exclude=decoder.metadata.reentrant(), file_name)
   gain = metadata.replaygain(_metadata)
 
   if
@@ -138,5 +138,7 @@ def enable_replaygain_metadata(~compute=true, ~ratio=50.) =
     end
   end
 
-  decoder.metadata.add("replaygain_track_gain", replaygain_metadata)
+  decoder.metadata.add(
+    reentrant=true, "replaygain_track_gain", replaygain_metadata
+  )
 end

tests/regression/GH4246.liq

@@ -0,0 +1,6 @@
+enable_replaygain_metadata()
+enable_autocue_metadata()
+
+audio = once(single("../media/@shine[channels=2].mp3"))
+
+output.dummy(fallible=true, on_start=test.pass, audio)

tests/regression/dune.inc

@@ -767,6 +767,22 @@
   (:run_test ../run_test.exe))
  (action (run %{run_test} GH4163.liq liquidsoap %{test_liq} GH4163.liq)))
 
+(rule
+ (alias citest)
+ (package liquidsoap)
+ (deps
+  GH4246.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} GH4246.liq liquidsoap %{test_liq} GH4246.liq)))
+
 (rule
  (alias citest)
  (package liquidsoap)