Add AsyncPropsManager JavaScript code generation

- Add async_props_setup_js helper method to generate AsyncPropsManager setup code
- Generate code when async_props_block is present in render_options
- Initialize AsyncPropsManager and store in sharedExecutionContext
- Add tests for both async_props_setup_js and render method

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: AbanoubGhadban

react_on_rails_pro/lib/react_on_rails_pro/server_rendering_js_code.rb

@@ -46,6 +46,21 @@ def generate_rsc_payload_js_function(render_options)
         JS
       end
 
+      # Generates JavaScript code for async props setup when incremental rendering is enabled
+      # @param render_options [Object] Options that control the rendering behavior
+      # @return [String] JavaScript code that sets up AsyncPropsManager or empty string
+      def async_props_setup_js(render_options)
+        return "" unless render_options.internal_option(:async_props_block)
+
+        <<-JS
+          if (ReactOnRails.isRSCBundle) {
+            var { props: propsWithAsyncProps, asyncPropManager } = ReactOnRails.addAsyncPropsCapabilityToComponentProps(usedProps);
+            usedProps = propsWithAsyncProps;
+            sharedExecutionContext.set("asyncPropsManager", asyncPropManager);
+          }
+        JS
+      end
+
       # Main rendering function that generates JavaScript code for server-side rendering
       # @param props_string [String] JSON string of props to pass to the React component
       # @param rails_context [String] JSON string of Rails context data
@@ -84,6 +99,7 @@ def render(props_string, rails_context, redux_stores, react_component_name, rend
           #{ssr_pre_hook_js}
           #{redux_stores}
           var usedProps = typeof props === 'undefined' ? #{props_string} : props;
+          #{async_props_setup_js(render_options)}
           return ReactOnRails[#{render_function_name}]({
             name: componentName,
             domNodeId: '#{render_options.dom_id}',

react_on_rails_pro/spec/react_on_rails_pro/server_rendering_js_code_spec.rb

@@ -0,0 +1,119 @@
+# frozen_string_literal: true
+
+require_relative "spec_helper"
+require "react_on_rails_pro/server_rendering_js_code"
+
+RSpec.describe ReactOnRailsPro::ServerRenderingJsCode do
+  describe ".async_props_setup_js" do
+    context "when async_props_block is NOT present in render_options" do
+      let(:render_options) do
+        instance_double(
+          ReactOnRails::ReactComponent::RenderOptions,
+          internal_option: nil
+        )
+      end
+
+      it "returns empty string" do
+        result = described_class.async_props_setup_js(render_options)
+
+        expect(result).to eq("")
+      end
+    end
+
+    context "when async_props_block is present in render_options" do
+      let(:async_props_block) { proc { { data: "async_data" } } }
+      let(:render_options) do
+        instance_double(
+          ReactOnRails::ReactComponent::RenderOptions,
+          internal_option: async_props_block
+        )
+      end
+
+      it "returns JavaScript code that sets up AsyncPropsManager" do
+        result = described_class.async_props_setup_js(render_options)
+
+        expect(result).to include("ReactOnRails.isRSCBundle")
+        expect(result).to include("ReactOnRails.addAsyncPropsCapabilityToComponentProps(usedProps)")
+        expect(result).to include("propsWithAsyncProps")
+        expect(result).to include("asyncPropManager")
+        expect(result).to include('sharedExecutionContext.set("asyncPropsManager", asyncPropManager)')
+        expect(result).to include("usedProps = propsWithAsyncProps")
+      end
+    end
+  end
+
+  describe ".render" do
+    let(:props_string) { '{"name":"Test"}' }
+    let(:rails_context) { '{"serverSide":true}' }
+    let(:redux_stores) { "" }
+    let(:react_component_name) { "TestComponent" }
+
+    context "when async_props_block is present" do
+      let(:async_props_block) { proc { { data: "async_data" } } }
+      let(:render_options) do
+        instance_double(
+          ReactOnRails::ReactComponent::RenderOptions,
+          internal_option: async_props_block,
+          streaming?: false,
+          dom_id: "TestComponent-0",
+          trace: false
+        )
+      end
+
+      before do
+        allow(ReactOnRailsPro.configuration).to receive(:enable_rsc_support).and_return(false)
+        allow(ReactOnRailsPro.configuration).to receive(:throw_js_errors).and_return(false)
+        allow(ReactOnRailsPro.configuration).to receive(:rendering_returns_promises).and_return(false)
+        allow(ReactOnRailsPro.configuration).to receive(:ssr_pre_hook_js).and_return(nil)
+      end
+
+      it "includes async props setup JavaScript in the generated code" do
+        result = described_class.render(
+          props_string,
+          rails_context,
+          redux_stores,
+          react_component_name,
+          render_options
+        )
+
+        expect(result).to include("var usedProps = typeof props === 'undefined' ?")
+        expect(result).to include("ReactOnRails.isRSCBundle")
+        expect(result).to include("ReactOnRails.addAsyncPropsCapabilityToComponentProps(usedProps)")
+        expect(result).to include('sharedExecutionContext.set("asyncPropsManager", asyncPropManager)')
+      end
+    end
+
+    context "when async_props_block is NOT present" do
+      let(:render_options) do
+        instance_double(
+          ReactOnRails::ReactComponent::RenderOptions,
+          internal_option: nil,
+          streaming?: false,
+          dom_id: "TestComponent-0",
+          trace: false
+        )
+      end
+
+      before do
+        allow(ReactOnRailsPro.configuration).to receive(:enable_rsc_support).and_return(false)
+        allow(ReactOnRailsPro.configuration).to receive(:throw_js_errors).and_return(false)
+        allow(ReactOnRailsPro.configuration).to receive(:rendering_returns_promises).and_return(false)
+        allow(ReactOnRailsPro.configuration).to receive(:ssr_pre_hook_js).and_return(nil)
+      end
+
+      it "does NOT include async props setup JavaScript in the generated code" do
+        result = described_class.render(
+          props_string,
+          rails_context,
+          redux_stores,
+          react_component_name,
+          render_options
+        )
+
+        expect(result).to include("var usedProps = typeof props === 'undefined' ?")
+        expect(result).not_to include("ReactOnRails.addAsyncPropsCapabilityToComponentProps")
+        expect(result).not_to include("asyncPropManager")
+      end
+    end
+  end
+end