vapoursynth: Simplify plugin loading (#332800)

pkgs/by-name/va/vapoursynth/nix-plugin-loader.patch

@@ -1,28 +0,0 @@
-diff --git a/src/core/vscore.cpp b/src/core/vscore.cpp
-index 73e2eafc..66a01326 100644
---- a/src/core/vscore.cpp
-+++ b/src/core/vscore.cpp
-@@ -1779,6 +1779,12 @@ void VSCore::isPortableInit() {
- }
- #endif
- 
-+void __attribute__((weak)) VSLoadPluginsNix(void (*load)(VSCore *core, const std::filesystem::path &), VSCore *);
-+
-+static void VSLoadPluginsNixCallback(VSCore *core, const std::filesystem::path &path) {
-+    core->loadAllPluginsInPath(path);
-+}
-+
- VSCore::VSCore(int flags) :
-     numFilterInstances(1),
-     numFunctionInstances(0),
-@@ -1890,6 +1896,10 @@ VSCore::VSCore(int flags) :
- #endif
-     }
- 
-+    if (VSLoadPluginsNix != nullptr) {
-+        VSLoadPluginsNix(VSLoadPluginsNixCallback, this);
-+    };
-+
-     VSMap *settings = readSettings(configFile);
-     const char *error = vs_internal_vsapi.mapGetError(settings);
-     if (error) {

pkgs/by-name/va/vapoursynth/package.nix

@@ -8,7 +8,6 @@
   runCommandCC,
   runCommand,
   vapoursynth,
-  writeText,
   buildEnv,
   zimg,
   libass,
@@ -29,8 +28,6 @@ stdenv.mkDerivation rec {
     hash = "sha256-T2bCVNH0dLM9lFYChXzvD6AJM3xEtOVCb2tI10tIXJs=";
   };
 
-  patches = [ ./nix-plugin-loader.patch ];
-
   nativeBuildInputs = [
     pkg-config
     autoreconfHook
@@ -53,6 +50,7 @@ stdenv.mkDerivation rec {
     ];
 
   enableParallelBuilding = true;
+  doInstallCheck = true;
 
   passthru = rec {
     # If vapoursynth is added to the build inputs of mpv and then
@@ -66,7 +64,6 @@ stdenv.mkDerivation rec {
         lib
         python3
         buildEnv
-        writeText
         runCommandCC
         stdenv
         runCommand
@@ -83,6 +80,14 @@ stdenv.mkDerivation rec {
     };
   };
 
+  postPatch = ''
+    # Export weak symbol nixPluginDir to permit override of default plugin path
+    sed -E -i \
+      -e 's/(VS_PATH_PLUGINDIR)/(nixPluginDir ? nixPluginDir : \1)/g' \
+      -e '1i\extern char const __attribute__((weak)) nixPluginDir[];' \
+      src/core/vscore.cpp
+  '';
+
   postInstall = ''
     wrapProgram $out/bin/vspipe \
         --prefix PYTHONPATH : $out/${python3.sitePackages}
@@ -92,6 +97,18 @@ stdenv.mkDerivation rec {
     mkdir $out/lib/vapoursynth
   '';
 
+  installCheckPhase = ''
+    runHook preInstallCheck
+
+    libv="$out/lib/libvapoursynth${stdenv.hostPlatform.extensions.sharedLibrary}"
+    if ! $NM -g -P "$libv" | grep -q '^nixPluginDir w'; then
+      echo "Weak symbol nixPluginDir is missing from $libv." >&2
+      exit 1
+    fi
+
+    runHook postInstallCheck
+  '';
+
   meta = with lib; {
     broken = stdenv.hostPlatform.isDarwin; # see https://github.com/NixOS/nixpkgs/pull/189446 for partial fix
     description = "Video processing framework with the future in mind";

pkgs/by-name/va/vapoursynth/plugin-interface.nix

@@ -2,7 +2,6 @@
   lib,
   python3,
   buildEnv,
-  writeText,
   runCommandCC,
   stdenv,
   runCommand,
@@ -35,29 +34,19 @@ let
     paths = deepPlugins;
   };
 
-  pluginLoader =
-    let
-      source = writeText "vapoursynth-nix-plugins.cpp" ''
-        #include <filesystem>
-
-        struct VSCore;
-
-        void VSLoadPluginsNix(void (*load)(VSCore *, const std::filesystem::path &), VSCore *core) {
-        ${lib.concatMapStrings (
-          path: ''load(core, std::filesystem::u8path("${path}/lib/vapoursynth"));''
-        ) deepPlugins}
-        }
-      '';
-    in
-    runCommandCC "vapoursynth-plugin-loader"
+  # Override default plugin path through nixPluginDir symbol
+  nixPlugins =
+    runCommandCC "libvapoursynth-nix-plugins${ext}"
       {
         executable = true;
         preferLocalBuild = true;
         allowSubstitutes = false;
+        src = ''
+          char const nixPluginDir[] = "${pluginsEnv}/lib/vapoursynth";
+        '';
       }
       ''
-        mkdir -p $out/lib
-        $CXX -std=c++17 -shared -fPIC ${source} -o "$out/lib/libvapoursynth-nix-plugins${ext}"
+        $CC -x c -shared -fPIC - -o "$out" <<<"$src"
       '';
 
   ext = stdenv.hostPlatform.extensions.sharedLibrary;
@@ -123,9 +112,7 @@ runCommand "${vapoursynth.name}-with-plugins"
             ${vapoursynth}/$binaryFile
     done
 
-    ln -s \
-        ${pluginLoader}/lib/libvapoursynth-nix-plugins${ext} \
-        $out/lib/libvapoursynth-nix-plugins${ext}
+    ln -s ${nixPlugins} $out/lib/libvapoursynth-nix-plugins${ext}
     ln -s ${vapoursynth}/include $out/include
     ln -s ${vapoursynth}/lib/vapoursynth/* $out/lib/vapoursynth
     ln -s \