Extract Codegen code from the react_native_pods to its own file (#34176)

Summary:
Pull Request resolved: #34176

It extracts the code related to the codegen from the main `react_native_pods` script to a dedicated file, adding also tests.

## Changelog

[iOS][Changed] - Move codegen in separate files

Differential Revision: D37755818

fbshipit-source-id: b0dccea0228abef532c63f0f7047bfe17ec170c8

Author: Riccardo Cipolleschi

scripts/cocoapods/__tests__/codegen-test.rb

@@ -10,6 +10,7 @@
 require_relative "./test_utils/FileMock.rb"
 require_relative "./test_utils/DirMock.rb"
 require_relative "./test_utils/systemUtils.rb"
+require_relative "./test_utils/CodegenUtilsMock.rb"
 
 class CodegenTests < Test::Unit::TestCase
     :third_party_provider_header
@@ -182,4 +183,60 @@ def testCheckAndGenerateEmptyThirdPartyProvider_whenBothMissing_buildCodegen()
             ]
         })
     end
+
+    # ================= #
+    # Test - RunCodegen #
+    # ================= #
+    def testRunCodegen_whenNewArchEnabled_runsCodegen
+        # Arrange
+        app_path = "~/app"
+        config_file = ""
+        codegen_utils_mock = CodegenUtilsMock.new()
+
+        # Act
+        run_codegen!(app_path, config_file, :new_arch_enabled => true, :codegen_utils => codegen_utils_mock)
+
+        # Assert
+        assert_equal(codegen_utils_mock.use_react_native_codegen_discovery_params, [{
+            :app_path=>"~/app",
+            :codegen_disabled=>false,
+            :codegen_output_dir=>"build/generated/ios",
+            :config_file_dir=>"",
+            :fabric_enabled=>false,
+            :react_native_path=>"../node_modules/react-native"
+        }])
+        assert_equal(codegen_utils_mock.get_react_codegen_spec_params, [])
+        assert_equal(codegen_utils_mock.generate_react_codegen_spec_params, [])
+    end
+
+    def testRunCodegen_whenNewArchDisabled_runsCodegen
+        # Arrange
+        app_path = "~/app"
+        config_file = ""
+        package_json_file = "~/app/package.json"
+        codegen_specs = { "name" => "React-Codegen" }
+        codegen_utils_mock = CodegenUtilsMock.new(:react_codegen_spec => codegen_specs)
+
+        # Act
+        run_codegen!(
+            app_path,
+            config_file,
+            :new_arch_enabled => false,
+            :fabric_enabled => true,
+            :package_json_file => package_json_file,
+            :codegen_utils => codegen_utils_mock)
+
+        # Assert
+        assert_equal(codegen_utils_mock.use_react_native_codegen_discovery_params, [])
+        assert_equal(codegen_utils_mock.get_react_codegen_spec_params, [{
+            :fabric_enabled => true,
+            :package_json_file => "~/app/package.json",
+            :script_phases => nil
+        }])
+        assert_equal(codegen_utils_mock.generate_react_codegen_spec_params, [{
+            :codegen_output_dir=>"build/generated/ios",
+            :react_codegen_spec=>{"name"=>"React-Codegen"}
+        }])
+
+    end
 end