build/chip/chip_codegen.gni - third_party/github/project-chip/connectedhomeip - Git at Google

 # Copyright (c) 2022 Project CHIP Authors
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 # http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.

 import("//build_overrides/build.gni")
 import("//build_overrides/chip.gni")
 import("//build_overrides/pigweed.gni")

 import("$dir_pw_build/python.gni")
 import("${chip_root}/scripts/py_matter_idl/files.gni")

 declare_args() {
   # Location where code has been pre-generated
   chip_code_pre_generated_directory = ""
 }

 # Code generation that will happen at build time.
 #
 # uses `scripts/codegen.py` for code generation.
 template("_chip_build_time_codegen") {
   _name = target_name
   _generator = invoker.generator

   config("${_name}_config") {
     include_dirs = [ target_gen_dir ]
   }

   pw_python_action("${_name}_codegen") {
     script = "${chip_root}/scripts/codegen.py"

     # TODO: this seems to touch internals. Is this ok? speeds up builds!
     _pw_internal_run_in_venv = false

     _idl_file = invoker.input
     _expected_outputs = "${target_gen_dir}/${_name}.expected.outputs"

     write_file(_expected_outputs, invoker.outputs, "list lines")

     args = [
       "--generator",
       _generator,
       "--output-dir",
       rebase_path(target_gen_dir, root_build_dir),
       "--expected-outputs",
       rebase_path(_expected_outputs, root_build_dir),
       rebase_path(_idl_file, root_build_dir),
     ]

     inputs = [
       _idl_file,
       _expected_outputs,
     ]

     # ensure any change in codegen files will result in a rebuild
     inputs += matter_idl_generator_files

     sources = [ _idl_file ]

     outputs = []
     foreach(name, invoker.outputs) {
       outputs += [ "${target_gen_dir}/${name}" ]
     }
   }

   source_set(_name) {
     sources = []
     foreach(name, invoker.outputs) {
       sources += [ "${target_gen_dir}/${name}" ]
     }

     public_configs = [ ":${_name}_config" ]

     if (defined(invoker.public_configs)) {
       public_configs += invoker.public_configs
     }

     forward_variables_from(invoker, [ "deps" ])

     if (!defined(deps)) {
       deps = []
     }
     deps += [ ":${_name}_codegen" ]
   }
 }

 # Code generation that will happen at build time.
 #
 # variables:
 #   input
 #     The ".zap" file to use to start the code generation
 #
 #   generator
 #     Name of the generator to use. Supported variants:
 #        - "app-templates"
 #
 #
 #
 #   deps, public_configs
 #     Forwarded to the resulting source set
 #
 #
 # uses `zap` for code generation.
 template("_chip_build_time_zapgen") {
   _name = target_name
   _generator = invoker.generator

   config("${_name}_config") {
     include_dirs = [ "${target_gen_dir}/zapgen/" ]
   }

   assert(_generator == "app-templates")

   if (_generator == "app-templates") {
     _template_path =
         rebase_path("${chip_root}/src/app/zap-templates/app-templates.json")

     _partials_dir = "${chip_root}/src/app/zap-templates/partials"
     _template_dir = "${chip_root}/src/app/zap-templates/templates/app"

     # TODO: unclear how to maintain these: there is no parser that can figure
     #       out links of template files and zap files and such
     _extra_dependencies = [
       "${_partials_dir}/header.zapt",
       "${_partials_dir}/im_command_handler_cluster_commands.zapt",

       # Application templates, actually generating files
       "${_template_dir}/access.zapt",
       "${_template_dir}/CHIPClientCallbacks.zapt",
       "${_template_dir}/CHIPClusters.zapt",
       "${_template_dir}/endpoint_config.zapt",
       "${_template_dir}/gen_config.zapt",
       "${_template_dir}/im-cluster-command-handler.zapt",
     ]

     _output_subdir = "zap-generated"
   }

   pw_python_action("${_name}_zap_pregen") {
     script = "${chip_root}/scripts/tools/zap/generate.py"

     # TODO: this seems to touch internals. Is this ok? speeds up builds!
     _pw_internal_run_in_venv = false

     _idl_file = invoker.input

     args = [
       "--no-prettify-output",
       "--templates",
       _template_path,
       "--output-dir",
       rebase_path(target_gen_dir) + "/zap_pregen/" + _output_subdir,

       # TODO: lock file support should be removed as this serializes zap
       # (slower), however this is currently done because on Darwin zap startup
       # may conflict and error out with:
       #    Error: EEXIST: file already exists, mkdir '/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/pkg/465fcc8a6282e28dc7a166859d5814d34e2fb94249a72fa9229033b5b32dff1a'
       "--lock-file",
       rebase_path("${root_out_dir}/zap_gen.lock"),
       "--parallel",
       _idl_file,
     ]

     inputs = [
       _idl_file,
       _template_path,
     ]
     inputs += _extra_dependencies

     # ensure any change in codegen files will result in a rebuild
     inputs += matter_idl_generator_files

     sources = [ _idl_file ]

     outputs = []
     foreach(name, invoker.outputs) {
       outputs += [ "${target_gen_dir}/zap_pregen/${name}" ]
     }

     forward_variables_from(invoker, [ "prune_outputs" ])
     if (defined(prune_outputs)) {
       foreach(name, prune_outputs) {
         outputs += [ "${target_gen_dir}/zap_pregen/${name}" ]
       }
     }
   }

   # This action ensures that any "extra" files generated by zap codegen
   # are actually deleted.
   #
   # This is to avoid double-codegen of configurations like endpoint config
   # or access credentials being generated for both "controller client" and
   # application-specific
   pw_python_action("${_name}_files") {
     # TODO: this seems to touch internals. Is this ok? speeds up builds!
     _pw_internal_run_in_venv = false

     script = "${chip_root}/scripts/tools/zap/prune_outputs.py"

     _keep_file = rebase_path("${target_gen_dir}/${_name}.keep.outputs")
     write_file(_keep_file, invoker.outputs, "list lines")

     args = [
       "--keep",
       _keep_file,
       "--input-dir",
       rebase_path("${target_gen_dir}/zap_pregen/"),
       "--output-dir",
       rebase_path("${target_gen_dir}/zapgen/"),
     ]

     inputs = []
     foreach(name, invoker.outputs) {
       inputs += [ "${target_gen_dir}/zap_pregen/${name}" ]
     }

     outputs = []
     foreach(name, invoker.outputs) {
       outputs += [ "${target_gen_dir}/zapgen/${name}" ]
     }

     deps = [ ":${_name}_zap_pregen" ]
   }

   source_set(_name) {
     sources = []
     foreach(name, invoker.outputs) {
       sources += [ "${target_gen_dir}/zapgen/${name}" ]
     }

     public_configs = [ ":${_name}_config" ]

     if (defined(invoker.public_configs)) {
       public_configs += invoker.public_configs
     }

     forward_variables_from(invoker, [ "deps" ])

     if (!defined(public_deps)) {
       public_deps = []
     }
     public_deps += [
       ":${_name}_files",
       ":${_name}_zap_pregen",
     ]
   }
 }

 # Defines a target that runs code generation based on
 # scripts/codegen.py
 #
 # Arguments:
 #   input
 #     The ".matter" file to use to start the code generation
 #
 #   generator
 #     Name of the generator to use (e.g. java-jni, java-class, cpp-app)
 #
 #   outputs
 #     Explicit names of the expected outputs. Enforced to validate that
 #     expected outputs are generated when processing input files.
 #
 #   deps, public_configs
 #     Forwarded to the resulting source set
 #
 # Command line parameters:
 #
 #  chip_code_pre_generated_directory:
 #     - If this is set, generation will NOT happen at compile time but rather
 #       the code generation is assumed to have already happened and reside in
 #       the given location.
 #     - The TOP LEVEL directory is assumed to be given. Actual location for
 #       individual generators is expected to be of the form
 #       <top_dir>/<matter_path>/<generator>
 #
 # NOTE: content of "outputs" is verified to match the output of codegen.py
 #       exactly. It is not inferred on purpose, to make build-rules explicit
 #       and verifiable (even though codegen.py can at runtime report its outputs)
 #
 #       To find the list of generated files, you can run codegen.py with the
 #       "--name-only" argument
 #
 # NOTE:
 #   the result of the target_name WILL BE a `source_set`. Treat it as such.
 #
 # Example usage:
 #
 #  chip_codegen("java-jni-generate") {
 #    input = "controller-clusters.matter"
 #    generator = "java-jni"
 #
 #    outputs = [
 #       "jni/IdentifyClient-ReadImpl.cpp",
 #       "jni/IdentifyClient-InvokeSubscribeImpl.cpp",
 #       # ... more to follow
 #    ]
 #  }
 #
 template("chip_codegen") {
   if (chip_code_pre_generated_directory == "") {
     _chip_build_time_codegen(target_name) {
       forward_variables_from(invoker,
                              [
                                "deps",
                                "generator",
                                "input",
                                "outputs",
                                "public_configs",
                              ])
     }
   } else {
     _name = target_name

     # This constructs a path like:
     #  FROM all-clusters-app.matter (inside examples/all-clusters-app/all-clusters-common/)
     #  USING "cpp-app" for generator:
     #    => ${pregen_dir}/examples/all-clusters-app/all-clusters-common/all-clusters-app/codegen/cpp-app
     _generation_dir =
         chip_code_pre_generated_directory + "/" +
         string_replace(rebase_path(invoker.input, chip_root), ".matter", "") +
         "/codegen/" + invoker.generator

     config("${_name}_config") {
       include_dirs = [ "${_generation_dir}" ]
     }

     source_set(_name) {
       public_configs = [ ":${_name}_config" ]

       if (defined(invoker.public_configs)) {
         public_configs += invoker.public_configs
       }

       forward_variables_from(invoker, [ "deps" ])

       sources = []
       foreach(name, invoker.outputs) {
         sources += [ "${_generation_dir}/${name}" ]
       }
     }
   }
 }

 # Defines a target that runs code generation based on
 # scripts/codegen.py
 #
 # Arguments:
 #   input
 #     The ".matter" file to use to start the code generation
 #
 #   generator
 #     Name of the generator to use (e.g. java-jni, java-class, cpp-app)
 #
 #   outputs
 #     Explicit names of the expected outputs. Enforced to validate that
 #     expected outputs are generated when processing input files.
 #
 #   deps, public_configs
 #     Forwarded to the resulting source set
 #
 # Command line parameters:
 #
 #  chip_code_pre_generated_directory:
 #     - If this is set, generation will NOT happen at compile time but rather
 #       the code generation is assumed to have already happened and reside in
 #       the given location.
 #     - The TOP LEVEL directory is assumed to be given. Actual location for
 #       individual generators is expected to be of the form
 #       <top_dir>/<matter_path>/<generator>
 #
 # NOTE: content of "outputs" is verified to match the output of codegen.py
 #       exactly. It is not inferred on purpose, to make build-rules explicit
 #       and verifiable (even though codegen.py can at runtime report its outputs)
 #
 #       To find the list of generated files, you can run codegen.py with the
 #       "--name-only" argument
 #
 # NOTE:
 #   the result of the target_name WILL BE a `source_set`. Treat it as such.
 #
 # Example usage:
 #
 #  chip_codegen("java-jni-generate") {
 #    input = "controller-clusters.matter"
 #    generator = "java-jni"
 #
 #    outputs = [
 #       "jni/IdentifyClient-ReadImpl.cpp",
 #       "jni/IdentifyClient-InvokeSubscribeImpl.cpp",
 #       # ... more to follow
 #    ]
 #  }
 #
 template("chip_zapgen") {
   if (chip_code_pre_generated_directory == "") {
     _chip_build_time_zapgen(target_name) {
       forward_variables_from(invoker,
                              [
                                "deps",
                                "generator",
                                "input",
                                "outputs",
                                "public_configs",
                                "prune_outputs",
                              ])
     }
   } else {
     _name = target_name

     # This contstructs a path like:
     #  FROM all-clusters-app.zap (inside examples/all-clusters-app/all-clusters-common/)
     #  USING "cpp-app" for generator:
     #    => ${pregen_dir}/examples/all-clusters-app/all-clusters-common/all-clusters-app/codegen/cpp-app
     _generation_dir =
         chip_code_pre_generated_directory + "/" +
         string_replace(rebase_path(invoker.input, chip_root), ".zap", "") +
         "/zap/" + invoker.generator

     config("${_name}_config") {
       include_dirs = [ "${_generation_dir}" ]
     }

     # Pick up only the headers and mark them available to use
     # Specifically controller seems to require header files but NOT cpp (does)
     # not want to include cpp compilation of IM command handler data
     source_set("${_name}_headers") {
       sources = []
       foreach(name, invoker.outputs) {
         if (get_path_info(name, "extension") == "h") {
           sources += [ "${_generation_dir}/${name}" ]
         }
       }

       # Ugly, but references WILL reference back into main code.
       check_includes = false
     }

     # need to have consistent naming. Make sure "files" exists
     action("${_name}_files") {
       script = "${chip_root}/scripts/tools/zap/check_file_existence.py"

       _output_name = "${target_gen_dir}/${_name}_files_checked.stamp"

       args = [
         "--touch",
         rebase_path(_output_name),
       ]
       outputs = [ _output_name ]

       foreach(name, invoker.outputs) {
         args += [
           "--exists",
           rebase_path("${_generation_dir}/${name}"),
         ]
       }

       # Depending on the files gets access to the headers
       public_deps = [ ":${_name}_headers" ]
     }

     source_set(_name) {
       forward_variables_from(invoker,
                              [
                                "deps",
                                "public_configs",
                                "prune_outputs",
                              ])
       if (!defined(public_configs)) {
         public_configs = []
       }
       public_configs += [ ":${_name}_config" ]

       sources = []
       foreach(name, invoker.outputs) {
         sources += [ "${_generation_dir}/${name}" ]
       }

       # Ugly, but references WILL reference back into main code.
       check_includes = false
     }
   }
 }
	# Copyright (c) 2022 Project CHIP Authors
	#
	# Licensed under the Apache License, Version 2.0 (the "License");
	# you may not use this file except in compliance with the License.
	# You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an "AS IS" BASIS,
	# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	# See the License for the specific language governing permissions and
	# limitations under the License.

	import("//build_overrides/build.gni")
	import("//build_overrides/chip.gni")
	import("//build_overrides/pigweed.gni")

	import("$dir_pw_build/python.gni")
	import("${chip_root}/scripts/py_matter_idl/files.gni")

	declare_args() {
	# Location where code has been pre-generated
	chip_code_pre_generated_directory = ""
	}

	# Code generation that will happen at build time.
	#
	# uses `scripts/codegen.py` for code generation.
	template("_chip_build_time_codegen") {
	_name = target_name
	_generator = invoker.generator

	config("${_name}_config") {
	include_dirs = [ target_gen_dir ]
	}

	pw_python_action("${_name}_codegen") {
	script = "${chip_root}/scripts/codegen.py"

	# TODO: this seems to touch internals. Is this ok? speeds up builds!
	_pw_internal_run_in_venv = false

	_idl_file = invoker.input
	_expected_outputs = "${target_gen_dir}/${_name}.expected.outputs"

	write_file(_expected_outputs, invoker.outputs, "list lines")

	args = [
	"--generator",
	_generator,
	"--output-dir",
	rebase_path(target_gen_dir, root_build_dir),
	"--expected-outputs",
	rebase_path(_expected_outputs, root_build_dir),
	rebase_path(_idl_file, root_build_dir),
	]

	inputs = [
	_idl_file,
	_expected_outputs,
	]

	# ensure any change in codegen files will result in a rebuild
	inputs += matter_idl_generator_files

	sources = [ _idl_file ]

	outputs = []
	foreach(name, invoker.outputs) {
	outputs += [ "${target_gen_dir}/${name}" ]
	}
	}

	source_set(_name) {
	sources = []
	foreach(name, invoker.outputs) {
	sources += [ "${target_gen_dir}/${name}" ]
	}

	public_configs = [ ":${_name}_config" ]

	if (defined(invoker.public_configs)) {
	public_configs += invoker.public_configs
	}

	forward_variables_from(invoker, [ "deps" ])

	if (!defined(deps)) {
	deps = []
	}
	deps += [ ":${_name}_codegen" ]
	}
	}

	# Code generation that will happen at build time.
	#
	# variables:
	# input
	# The ".zap" file to use to start the code generation
	#
	# generator
	# Name of the generator to use. Supported variants:
	# - "app-templates"
	#
	#
	#
	# deps, public_configs
	# Forwarded to the resulting source set
	#
	#
	# uses `zap` for code generation.
	template("_chip_build_time_zapgen") {
	_name = target_name
	_generator = invoker.generator

	config("${_name}_config") {
	include_dirs = [ "${target_gen_dir}/zapgen/" ]
	}

	assert(_generator == "app-templates")

	if (_generator == "app-templates") {
	_template_path =
	rebase_path("${chip_root}/src/app/zap-templates/app-templates.json")

	_partials_dir = "${chip_root}/src/app/zap-templates/partials"
	_template_dir = "${chip_root}/src/app/zap-templates/templates/app"

	# TODO: unclear how to maintain these: there is no parser that can figure
	# out links of template files and zap files and such
	_extra_dependencies = [
	"${_partials_dir}/header.zapt",
	"${_partials_dir}/im_command_handler_cluster_commands.zapt",

	# Application templates, actually generating files
	"${_template_dir}/access.zapt",
	"${_template_dir}/CHIPClientCallbacks.zapt",
	"${_template_dir}/CHIPClusters.zapt",
	"${_template_dir}/endpoint_config.zapt",
	"${_template_dir}/gen_config.zapt",
	"${_template_dir}/im-cluster-command-handler.zapt",
	]

	_output_subdir = "zap-generated"
	}

	pw_python_action("${_name}_zap_pregen") {
	script = "${chip_root}/scripts/tools/zap/generate.py"

	# TODO: this seems to touch internals. Is this ok? speeds up builds!
	_pw_internal_run_in_venv = false

	_idl_file = invoker.input

	args = [
	"--no-prettify-output",
	"--templates",
	_template_path,
	"--output-dir",
	rebase_path(target_gen_dir) + "/zap_pregen/" + _output_subdir,

	# TODO: lock file support should be removed as this serializes zap
	# (slower), however this is currently done because on Darwin zap startup
	# may conflict and error out with:
	# Error: EEXIST: file already exists, mkdir '/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/pkg/465fcc8a6282e28dc7a166859d5814d34e2fb94249a72fa9229033b5b32dff1a'
	"--lock-file",
	rebase_path("${root_out_dir}/zap_gen.lock"),
	"--parallel",
	_idl_file,
	]

	inputs = [
	_idl_file,
	_template_path,
	]
	inputs += _extra_dependencies

	# ensure any change in codegen files will result in a rebuild
	inputs += matter_idl_generator_files

	sources = [ _idl_file ]

	outputs = []
	foreach(name, invoker.outputs) {
	outputs += [ "${target_gen_dir}/zap_pregen/${name}" ]
	}

	forward_variables_from(invoker, [ "prune_outputs" ])
	if (defined(prune_outputs)) {
	foreach(name, prune_outputs) {
	outputs += [ "${target_gen_dir}/zap_pregen/${name}" ]
	}
	}
	}

	# This action ensures that any "extra" files generated by zap codegen
	# are actually deleted.
	#
	# This is to avoid double-codegen of configurations like endpoint config
	# or access credentials being generated for both "controller client" and
	# application-specific
	pw_python_action("${_name}_files") {
	# TODO: this seems to touch internals. Is this ok? speeds up builds!
	_pw_internal_run_in_venv = false

	script = "${chip_root}/scripts/tools/zap/prune_outputs.py"

	_keep_file = rebase_path("${target_gen_dir}/${_name}.keep.outputs")
	write_file(_keep_file, invoker.outputs, "list lines")

	args = [
	"--keep",
	_keep_file,
	"--input-dir",
	rebase_path("${target_gen_dir}/zap_pregen/"),
	"--output-dir",
	rebase_path("${target_gen_dir}/zapgen/"),
	]

	inputs = []
	foreach(name, invoker.outputs) {
	inputs += [ "${target_gen_dir}/zap_pregen/${name}" ]
	}

	outputs = []
	foreach(name, invoker.outputs) {
	outputs += [ "${target_gen_dir}/zapgen/${name}" ]
	}

	deps = [ ":${_name}_zap_pregen" ]
	}

	source_set(_name) {
	sources = []
	foreach(name, invoker.outputs) {
	sources += [ "${target_gen_dir}/zapgen/${name}" ]
	}

	public_configs = [ ":${_name}_config" ]

	if (defined(invoker.public_configs)) {
	public_configs += invoker.public_configs
	}

	forward_variables_from(invoker, [ "deps" ])

	if (!defined(public_deps)) {
	public_deps = []
	}
	public_deps += [
	":${_name}_files",
	":${_name}_zap_pregen",
	]
	}
	}

	# Defines a target that runs code generation based on
	# scripts/codegen.py
	#
	# Arguments:
	# input
	# The ".matter" file to use to start the code generation
	#
	# generator
	# Name of the generator to use (e.g. java-jni, java-class, cpp-app)
	#
	# outputs
	# Explicit names of the expected outputs. Enforced to validate that
	# expected outputs are generated when processing input files.
	#
	# deps, public_configs
	# Forwarded to the resulting source set
	#
	# Command line parameters:
	#
	# chip_code_pre_generated_directory:
	# - If this is set, generation will NOT happen at compile time but rather
	# the code generation is assumed to have already happened and reside in
	# the given location.
	# - The TOP LEVEL directory is assumed to be given. Actual location for
	# individual generators is expected to be of the form
	# <top_dir>/<matter_path>/<generator>
	#
	# NOTE: content of "outputs" is verified to match the output of codegen.py
	# exactly. It is not inferred on purpose, to make build-rules explicit
	# and verifiable (even though codegen.py can at runtime report its outputs)
	#
	# To find the list of generated files, you can run codegen.py with the
	# "--name-only" argument
	#
	# NOTE:
	# the result of the target_name WILL BE a `source_set`. Treat it as such.
	#
	# Example usage:
	#
	# chip_codegen("java-jni-generate") {
	# input = "controller-clusters.matter"
	# generator = "java-jni"
	#
	# outputs = [
	# "jni/IdentifyClient-ReadImpl.cpp",
	# "jni/IdentifyClient-InvokeSubscribeImpl.cpp",
	# # ... more to follow
	# ]
	# }
	#
	template("chip_codegen") {
	if (chip_code_pre_generated_directory == "") {
	_chip_build_time_codegen(target_name) {
	forward_variables_from(invoker,
	[
	"deps",
	"generator",
	"input",
	"outputs",
	"public_configs",
	])
	}
	} else {
	_name = target_name

	# This constructs a path like:
	# FROM all-clusters-app.matter (inside examples/all-clusters-app/all-clusters-common/)
	# USING "cpp-app" for generator:
	# => ${pregen_dir}/examples/all-clusters-app/all-clusters-common/all-clusters-app/codegen/cpp-app
	_generation_dir =
	chip_code_pre_generated_directory + "/" +
	string_replace(rebase_path(invoker.input, chip_root), ".matter", "") +
	"/codegen/" + invoker.generator

	config("${_name}_config") {
	include_dirs = [ "${_generation_dir}" ]
	}

	source_set(_name) {
	public_configs = [ ":${_name}_config" ]

	if (defined(invoker.public_configs)) {
	public_configs += invoker.public_configs
	}

	forward_variables_from(invoker, [ "deps" ])

	sources = []
	foreach(name, invoker.outputs) {
	sources += [ "${_generation_dir}/${name}" ]
	}
	}
	}
	}

	# Defines a target that runs code generation based on
	# scripts/codegen.py
	#
	# Arguments:
	# input
	# The ".matter" file to use to start the code generation
	#
	# generator
	# Name of the generator to use (e.g. java-jni, java-class, cpp-app)
	#
	# outputs
	# Explicit names of the expected outputs. Enforced to validate that
	# expected outputs are generated when processing input files.
	#
	# deps, public_configs
	# Forwarded to the resulting source set
	#
	# Command line parameters:
	#
	# chip_code_pre_generated_directory:
	# - If this is set, generation will NOT happen at compile time but rather
	# the code generation is assumed to have already happened and reside in
	# the given location.
	# - The TOP LEVEL directory is assumed to be given. Actual location for
	# individual generators is expected to be of the form
	# <top_dir>/<matter_path>/<generator>
	#
	# NOTE: content of "outputs" is verified to match the output of codegen.py
	# exactly. It is not inferred on purpose, to make build-rules explicit
	# and verifiable (even though codegen.py can at runtime report its outputs)
	#
	# To find the list of generated files, you can run codegen.py with the
	# "--name-only" argument
	#
	# NOTE:
	# the result of the target_name WILL BE a `source_set`. Treat it as such.
	#
	# Example usage:
	#
	# chip_codegen("java-jni-generate") {
	# input = "controller-clusters.matter"
	# generator = "java-jni"
	#
	# outputs = [
	# "jni/IdentifyClient-ReadImpl.cpp",
	# "jni/IdentifyClient-InvokeSubscribeImpl.cpp",
	# # ... more to follow
	# ]
	# }
	#
	template("chip_zapgen") {
	if (chip_code_pre_generated_directory == "") {
	_chip_build_time_zapgen(target_name) {
	forward_variables_from(invoker,
	[
	"deps",
	"generator",
	"input",
	"outputs",
	"public_configs",
	"prune_outputs",
	])
	}
	} else {
	_name = target_name

	# This contstructs a path like:
	# FROM all-clusters-app.zap (inside examples/all-clusters-app/all-clusters-common/)
	# USING "cpp-app" for generator:
	# => ${pregen_dir}/examples/all-clusters-app/all-clusters-common/all-clusters-app/codegen/cpp-app
	_generation_dir =
	chip_code_pre_generated_directory + "/" +
	string_replace(rebase_path(invoker.input, chip_root), ".zap", "") +
	"/zap/" + invoker.generator

	config("${_name}_config") {
	include_dirs = [ "${_generation_dir}" ]
	}

	# Pick up only the headers and mark them available to use
	# Specifically controller seems to require header files but NOT cpp (does)
	# not want to include cpp compilation of IM command handler data
	source_set("${_name}_headers") {
	sources = []
	foreach(name, invoker.outputs) {
	if (get_path_info(name, "extension") == "h") {
	sources += [ "${_generation_dir}/${name}" ]
	}
	}

	# Ugly, but references WILL reference back into main code.
	check_includes = false
	}

	# need to have consistent naming. Make sure "files" exists
	action("${_name}_files") {
	script = "${chip_root}/scripts/tools/zap/check_file_existence.py"

	_output_name = "${target_gen_dir}/${_name}_files_checked.stamp"

	args = [
	"--touch",
	rebase_path(_output_name),
	]
	outputs = [ _output_name ]

	foreach(name, invoker.outputs) {
	args += [
	"--exists",
	rebase_path("${_generation_dir}/${name}"),
	]
	}

	# Depending on the files gets access to the headers
	public_deps = [ ":${_name}_headers" ]
	}

	source_set(_name) {
	forward_variables_from(invoker,
	[
	"deps",
	"public_configs",
	"prune_outputs",
	])
	if (!defined(public_configs)) {
	public_configs = []
	}
	public_configs += [ ":${_name}_config" ]

	sources = []
	foreach(name, invoker.outputs) {
	sources += [ "${_generation_dir}/${name}" ]
	}

	# Ugly, but references WILL reference back into main code.
	check_includes = false
	}
	}
	}