commit cd7026359549cf0ee6efa7de256c52e31a80e3de
Author: Simon Bruder <simon@sbruder.de>
Date:   Thu Jan 21 15:53:58 2021 +0100

    vapoursynth: add withPlugins interface
    
    Since nixpkgs does not currently have an attribute set with plugins, the
    usage differes from python-style withPackages as it accepts a list
    instead of a function as a parameter.
    
    Using plugins in other programs that require vapoursynth (like `vsedit`)
    can be achieved by adding it to the plugin list (e.g.
    `vapoursynth.withPlugins [ vapoursynth-editor … ]`) or by passing the
    `VAPOURSYNTH_PLUGIN_PATH` variable.

diff --git a/pkgs/development/libraries/vapoursynth/default.nix b/pkgs/development/libraries/vapoursynth/default.nix
index 93f8d3c5ae5..6723868746d 100644
--- a/pkgs/development/libraries/vapoursynth/default.nix
+++ b/pkgs/development/libraries/vapoursynth/default.nix
@@ -1,4 +1,6 @@
-{ lib, stdenv, fetchFromGitHub, pkg-config, autoreconfHook, makeWrapper
+{ lib, stdenv, fetchFromGitHub, pkg-config, autoreconfHook
+, symlinkJoin, makeWrapper
+, vapoursynth
 , zimg, libass, python3, libiconv
 , ApplicationServices
 , ocrSupport ?  false, tesseract ? null
@@ -21,6 +23,10 @@ stdenv.mkDerivation rec {
     sha256 = "1krfdzc2x2vxv4nq9kiv1c09hgj525qn120ah91fw2ikq8ldvmx4";
   };
 
+  patches = [
+    ./plugin-path-environment-variable.patch
+  ];
+
   nativeBuildInputs = [ pkg-config autoreconfHook makeWrapper ];
   buildInputs = [
     zimg libass
@@ -42,6 +48,30 @@ stdenv.mkDerivation rec {
     # wrapper, what python3 version was used to build vapoursynth so
     # the right python3.sitePackages will be used there.
     inherit python3;
+
+    withPlugins = plugins:
+      let
+        pythonEnvironment = python3.buildEnv.override { extraLibs = plugins; };
+      in
+      symlinkJoin {
+        name = "${vapoursynth.name}-with-plugins";
+        paths = [ vapoursynth ] ++ plugins;
+        buildInputs = [ makeWrapper ];
+        postBuild = ''
+          for symlink in $out/bin/*; do
+            # remove the original symlink
+            original="$(realpath "$symlink")"
+            rm "$symlink"
+
+            makeWrapper "$original" "$symlink" \
+              --set VAPOURSYNTH_PLUGIN_PATH $out/lib/vapoursynth \
+              --prefix PYTHONPATH : ${pythonEnvironment}/${python3.sitePackages}
+          done
+        '';
+
+        # passthrus must be specified here, again
+        passthru = { inherit python3; };
+      };
   };
 
   postInstall = ''
@@ -54,7 +84,6 @@ stdenv.mkDerivation rec {
     homepage    = "http://www.vapoursynth.com/";
     license     = licenses.lgpl21;
     platforms   = platforms.x86_64;
-    maintainers = with maintainers; [ rnhmjoj tadeokondrak ];
+    maintainers = with maintainers; [ rnhmjoj sbruder tadeokondrak ];
   };
-
 }
diff --git a/pkgs/development/libraries/vapoursynth/plugin-path-environment-variable.patch b/pkgs/development/libraries/vapoursynth/plugin-path-environment-variable.patch
new file mode 100644
index 00000000000..80f98633d7f
--- /dev/null
+++ b/pkgs/development/libraries/vapoursynth/plugin-path-environment-variable.patch
@@ -0,0 +1,16 @@
+diff --git a/src/core/vscore.cpp b/src/core/vscore.cpp
+index 2d29844d..fd4cbea5 100644
+--- a/src/core/vscore.cpp
++++ b/src/core/vscore.cpp
+@@ -1351,6 +1351,11 @@ VSCore::VSCore(int threads) :
+     } // If neither exists, an empty string will do.
+ #endif
+ 
++    const char *pluginPath = getenv("VAPOURSYNTH_PLUGIN_PATH");
++    if (pluginPath) {
++        loadAllPluginsInPath((std::string)pluginPath, filter);
++    }
++
+     VSMap *settings = readSettings(configFile);
+     const char *error = vs_internal_vsapi.getError(settings);
+     if (error) {

diff --git a/pkgs/development/libraries/vapoursynth/default.nix b/pkgs/development/libraries/vapoursynth/default.nix
index 2bc0d00b521..70fd297610a 100644
--- a/pkgs/development/libraries/vapoursynth/default.nix
+++ b/pkgs/development/libraries/vapoursynth/default.nix
@@ -1,5 +1,5 @@
 { lib, stdenv, fetchFromGitHub, pkg-config, autoreconfHook, makeWrapper
-, runCommandCC, runCommand, vapoursynth, writeText, patchelf
+, runCommandCC, runCommand, vapoursynth, writeText, patchelf, buildEnv
 , zimg, libass, python3, libiconv
 , ApplicationServices
 , ocrSupport ?  false, tesseract ? null
@@ -60,6 +60,12 @@ stdenv.mkDerivation rec {
 
       deepPlugins = plugins ++ (getRecursivePropagatedBuildInputs plugins);
 
+      pluginsEnv = buildEnv {
+        name = "vapoursynth-plugins-env";
+        pathsToLink = [ "/lib/vapoursynth" ];
+        paths = deepPlugins;
+      };
+
       pluginLoader = let
         source = writeText "vapoursynth-nix-plugins.c" ''
           void VSLoadPluginsNix(void (*load)(void *data, const char *path), void *data) {
@@ -102,6 +108,10 @@ stdenv.mkDerivation rec {
               --replace "${vapoursynth}" "$out"
       done
 
+      for binaryPlugin in ${pluginsEnv}/lib/vapoursynth/*; do
+          ln -s $binaryPlugin $out/''${binaryPlugin#"${pluginsEnv}/"}
+      done
+
       for pythonPlugin in ${pythonEnvironment}/${python3.sitePackages}/*; do
           ln -s $pythonPlugin $out/''${pythonPlugin#"${pythonEnvironment}/"}
       done