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diff --git a/nix/mergePatch/default.nix b/nix/mergePatch/default.nix
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+{ lib, depot, ... }:
+/*
+  JSON Merge-Patch for nix
+  Spec: https://tools.ietf.org/html/rfc7396
+
+  An algorithm for changing and removing fields in nested objects.
+
+  For example, given the following original document:
+
+  {
+  a = "b";
+  c = {
+      d = "e";
+      f = "g";
+  }
+  }
+
+  Changing the value of `a` and removing `f` can be achieved by merging the patch
+
+  {
+  a = "z";
+  c.f = null;
+  }
+
+  which results in
+
+  {
+  a = "z";
+  c = {
+      d = "e";
+  };
+  }
+
+  Pseudo-code:
+  define MergePatch(Target, Patch):
+      if Patch is an Object:
+        if Target is not an Object:
+          Target = {} # Ignore the contents and set it to an empty Object
+        for each Name/Value pair in Patch:
+          if Value is null:
+            if Name exists in Target:
+              remove the Name/Value pair from Target
+          else:
+            Target[Name] = MergePatch(Target[Name], Value)
+        return Target
+      else:
+        return Patch
+*/
+
+let
+  foldlAttrs = op: init: attrs:
+    lib.foldl' op init
+      (lib.mapAttrsToList lib.nameValuePair attrs);
+
+  mergePatch = target: patch:
+    if lib.isAttrs patch
+    then
+      let target' = if lib.isAttrs target then target else { };
+      in foldlAttrs
+        (acc: patchEl:
+          if patchEl.value == null
+          then removeAttrs acc [ patchEl.name ]
+          else acc // {
+            ${patchEl.name} =
+              mergePatch
+                (acc.${patchEl.name} or "unnused")
+                patchEl.value;
+          })
+        target'
+        patch
+    else patch;
+
+  inherit (depot.nix.runTestsuite)
+    runTestsuite
+    it
+    assertEq
+    ;
+
+  tests =
+    let
+      # example target from the RFC
+      testTarget = {
+        a = "b";
+        c = {
+          d = "e";
+          f = "g";
+        };
+      };
+      # example patch from the RFC
+      testPatch = {
+        a = "z";
+        c.f = null;
+      };
+      emptyPatch = it "the empty patch returns the original target" [
+        (assertEq "id"
+          (mergePatch testTarget { })
+          testTarget)
+      ];
+      nonAttrs = it "one side is a non-attrset value" [
+        (assertEq "target is a value means the value is replaced by the patch"
+          (mergePatch 42 testPatch)
+          (mergePatch { } testPatch))
+        (assertEq "patch is a value means it replaces target alltogether"
+          (mergePatch testTarget 42)
+          42)
+      ];
+      rfcExamples = it "the examples from the RFC" [
+        (assertEq "a subset is deleted and overwritten"
+          (mergePatch testTarget testPatch)
+          {
+            a = "z";
+            c = {
+              d = "e";
+            };
+          })
+        (assertEq "a more complicated example from the example section"
+          (mergePatch
+            {
+              title = "Goodbye!";
+              author = {
+                givenName = "John";
+                familyName = "Doe";
+              };
+              tags = [ "example" "sample" ];
+              content = "This will be unchanged";
+            }
+            {
+              title = "Hello!";
+              phoneNumber = "+01-123-456-7890";
+              author.familyName = null;
+              tags = [ "example" ];
+            })
+          {
+            title = "Hello!";
+            phoneNumber = "+01-123-456-7890";
+            author = {
+              givenName = "John";
+            };
+            tags = [ "example" ];
+            content = "This will be unchanged";
+          })
+      ];
+
+      rfcTests =
+        let
+          r = index: target: patch: res:
+            (assertEq "test number ${toString index}"
+              (mergePatch target patch)
+              res);
+        in
+        it "the test suite from the RFC" [
+          (r 1 { "a" = "b"; } { "a" = "c"; } { "a" = "c"; })
+          (r 2 { "a" = "b"; } { "b" = "c"; } { "a" = "b"; "b" = "c"; })
+          (r 3 { "a" = "b"; } { "a" = null; } { })
+          (r 4 { "a" = "b"; "b" = "c"; }
+            { "a" = null; }
+            { "b" = "c"; })
+          (r 5 { "a" = [ "b" ]; } { "a" = "c"; } { "a" = "c"; })
+          (r 6 { "a" = "c"; } { "a" = [ "b" ]; } { "a" = [ "b" ]; })
+          (r 7 { "a" = { "b" = "c"; }; }
+            { "a" = { "b" = "d"; "c" = null; }; }
+            { "a" = { "b" = "d"; }; })
+          (r 8 { "a" = [{ "b" = "c"; }]; }
+            { "a" = [ 1 ]; }
+            { "a" = [ 1 ]; })
+          (r 9 [ "a" "b" ] [ "c" "d" ] [ "c" "d" ])
+          (r 10 { "a" = "b"; } [ "c" ] [ "c" ])
+          (r 11 { "a" = "foo"; } null null)
+          (r 12 { "a" = "foo"; } "bar" "bar")
+          (r 13 { "e" = null; } { "a" = 1; } { "e" = null; "a" = 1; })
+          (r 14 [ 1 2 ]
+            { "a" = "b"; "c" = null; }
+            { "a" = "b"; })
+          (r 15 { }
+            { "a" = { "bb" = { "ccc" = null; }; }; }
+            { "a" = { "bb" = { }; }; })
+        ];
+
+    in
+    runTestsuite "mergePatch" [
+      emptyPatch
+      nonAttrs
+      rfcExamples
+      rfcTests
+    ];
+
+in
+{
+  __functor = _: mergePatch;
+
+  inherit tests;
+}