New code generation documentation

README.md

@@ -29,9 +29,7 @@ pip install -r requirements.txt -c constraints.txt
 
 ### Pinned versions
 
-For development we currently use Jammy as our build platform.
-And all python versions are pinned in the constraints file to make sure that things are reproducible.
-To upgrade the system validate that things are working and then use `pip freeze > constraints.txt` to lock in the versions to upgrade.
+For development we currently use Jammy as our build platform. ANd all python versions are pinned in the constraints file to make sure that things are reproducible. To upgrade the system validate that things are working and then use `pip freeze > constraints.txt` to lock in the versions to upgrade.
 
 ## Building HTML
 

source/Concepts/Advanced/About-Internal-Interfaces.rst

@@ -201,16 +201,20 @@ of CMake and Ament. To simplify the explanation of this mechanism let's separate
 -  ``Generator`` projects, which are the ones that have the templates and logic to generate code.
 -  ``Interface`` projects, which are the ones that need code to be generated, they have the parameters to generate code.
 
-For instance, typesupport packages that generate code for a particular dds implementation are *Generator* packages, same case that rosidl which
+For instance, typesupport packages that generate code for a particular dds implementation are ``Generator`` packages, same case that rosidl which
 generates code from ros idl (.msg, .action, etc) files.
 
-*Interface* projects are typically projects that define messages, actions and services. Which have .msg files with rosidl defined on them which are
-used by *Generator* projects to create code. A package that calls rosidl_generate_interfaces CMake macro is a *Interface* project.
+``Interface`` projects are typically projects that define messages, actions and services. Which have .msg files with rosidl defined on them which are
+used by ``Interface`` projects to crete code. A package that calls rosidl_generate_interfaces CMake macro is a ``Interface`` project.
 
 Code generation workflow
-------------------------
+-------------------------
+
+On workspace build, the ``generator`` packages, registers portions of CMake code as an ament_extension under different keys:
 
-On workspace build, the *generator* packages, registers a portion of CMake code as an ament_extension under 'rosidl_generate_idl_interfaces' key.
+-  ``rosidl_create_type_descriptions_extensions`` : Calls type support description extensions(generate hashes for typessupports)
+-  ``rosidl_write_generator_arguments_extensions``: Generate the arguments files.
+-  ``rosidl_generate_idl_interfaces``: After files are generated, create artifacts, export dependencies.
 
 Hook registration on CodeGenerator project build
 
@@ -221,28 +225,40 @@ Hook registration on CodeGenerator project build
     participant ament_package
     participant ament_register_extension
     CodeGenerator_cmake->>ament_package: CONFIG_EXTRAS
+    ament_package->>ament_register_extension: rosidl_create_type_descriptions_extensions, cmake_code_hook
+    ament_package->>ament_register_extension: rosidl_write_generator_arguments_extensions, cmake_code_hook
     ament_package->>ament_register_extension: rosidl_generate_idl_interfaces, cmake_code_hook
     Note right of ament_package: Execute a cmake.in template with variables and a cmake code hook.
 
 
-When the *interface* package, during its build process, calls the 'rosidl_generate_interfaces' macro, the extensions that were registered for each of the
-*generator* packages, get called. Said extensions have the code to generate sources for each of the IDL interfaces. Then, code is added to an artifact
-(a library) and dependiences are exported for code to be build and installed.
+When the ``interface`` package, during its build process, calls the 'rosidl_generate_interfaces' macro, the extensions that were registered for each of the
+``generator`` packages, get called. On 'rosidl_write_generator_arguments_extensions' arguments files are generated with all parameters required to call the templates engine.
+After collecting all the arguments files, the extension calls the template engine for all the arguments files at once. Once code is generated,
+the 'rosidl_generate_idl_interfaces' extensiones are called to get code added to an artifact (a library) and export dependiences.
 
 .. mermaid::
 
     sequenceDiagram
     participant project_with_rosidl_files
     participant rosidl_generate_interfaces
+    participant rosidl_create_type_descriptions_extensions_HOOK
     participant rosidl_generate_idl_interfaces_HOOK
+    participant rosidl_write_generator_arguments_extensions_HOOK
     participant generate_arguments_file
     participant rosidl_generator
     project_with_rosidl_files->>rosidl_generate_interfaces: path_to_idl_files
-    loop ForEach Hook
-        rosidl_generate_interfaces->>rosidl_generate_idl_interfaces_HOOK: path_to_idl_files, parameters
-        rosidl_generate_idl_interfaces_HOOK->>generate_arguments_file: template_parameters
+    loop ForEach rosidl_create_type_descriptions_extensions Hook
+        rosidl_generate_interfaces->>rosidl_create_type_descriptions_extensions_HOOK: path_to_idl_files, parameters
+    end
+    loop ForEach rosidl_write_generator_arguments_extensions Hook
+        rosidl_generate_interfaces->>rosidl_write_generator_arguments_extensions_HOOK: path_to_idl_files, parameters
         activate generate_arguments_file
-        generate_arguments_file->>rosidl_generate_idl_interfaces_HOOK: arguments_file
+        rosidl_write_generator_arguments_extensions_HOOK->>generate_arguments_file: path_to_idl_files, parameters
+        generate_arguments_file->>rosidl_write_generator_arguments_extensions_HOOK: arguments_file
         deactivate generate_arguments_file
-        rosidl_generate_idl_interfaces_HOOK->>rosidl_generator: arguments_file
+        rosidl_write_generator_arguments_extensions_HOOK->>rosidl_generate_interfaces: arguments_file
+    end
+    rosidl_generate_interfaces->>rosidl_generator: [arguments_files]
+    loop ForEach rosidl_generate_idl_interfaces Hook
+        rosidl_generate_interfaces->>rosidl_generate_idl_interfaces_HOOK: generated_files
     end