fix: carry hook context between before and after hooks

lib/open_feature/client.ex

@@ -258,7 +258,7 @@ defmodule OpenFeature.Client do
     }
 
     try do
-      before_hooks(all_hooks, hook_context, opts)
+      hook_context = before_hooks(all_hooks, hook_context, opts)
 
       short_circuit_if_not_ready(client)
 
@@ -341,10 +341,19 @@ defmodule OpenFeature.Client do
   defp before_hooks(hooks, hook_context, opts) do
     hook_hints = Keyword.get(opts, :hook_hints, %{})
 
-    Enum.each(hooks, fn
-      %Hook{before: nil} -> :ok
-      %Hook{before: before} -> before.(hook_context, hook_hints)
-    end)
+    context =
+      Enum.reduce(hooks, hook_context.context, fn
+        %Hook{before: nil}, context ->
+          context
+
+        %Hook{before: before}, context ->
+          case before.(hook_context, hook_hints) do
+            data when is_map(data) -> Map.merge(context, data)
+            _other -> context
+          end
+      end)
+
+    Map.put(hook_context, :context, context)
   end
 
   defp after_hooks(hooks, hook_context, evaluation_details, opts) do

test/unit/open_feature/client_test.exs

@@ -255,6 +255,37 @@ defmodule OpenFeature.ClientTest do
       assert_receive :hook_called
     end
 
+    test "context from before hook is carried to after hook", %{client: client} do
+      parent = self()
+      context = %{key: "value"}
+      key = "key"
+      default = true
+
+      hook = %Hook{
+        before: fn _hook_context, _hints ->
+          send(parent, :before_hook_called)
+          %{key: "other data"}
+        end,
+        after: fn hook_context, _details, _hints ->
+          assert_receive :provider_called
+          assert hook_context.context[:key] == "other data"
+          send(parent, :after_hook_called)
+        end
+      }
+
+      expect(Provider, :resolve_value, 1, fn _provider, _type, _key, _default, _context ->
+        assert_receive :before_hook_called
+        send(parent, :provider_called)
+        {:ok, %ResolutionDetails{value: true}}
+      end)
+
+      client = Client.add_hooks(client, [hook])
+
+      Client.get_boolean_value(client, key, default, context: context)
+
+      assert_receive :after_hook_called
+    end
+
     test "does not resolve value if an error occurs in before hooks", %{client: client} do
       parent = self()
       context = %{key: "value"}