dawn-cmake/generator/generator_lib.gni

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# Copyright 2019 The Dawn 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.
# Template to help invoking code generators based on generator_lib.py
# Internal use only, this should only be called from templates implementing
# generator-specific actions.
#
# Variables:
# script: Path to generator script.
#
# args: List of extra command-line arguments passed to the generator.
#
# outputs: List of expected outputs, generation will fail if there is a
# mistmatch.
#
# generator_lib_dir: directory where generator_lib.py is located.
#
# custom_gen_dir: Optional custom target gen dir. Defaults to $target_gen_dir
# but allows output files to not depend on the location of the BUILD.gn
# that generates them.
#
# template_dir: Optional template root directory. Defaults to
# "${generator_lib_dir}/templates".
#
# jinja2_path: Optional Jinja2 installation path.
#
# allowed_output_dirs: Optional list of directories that are the only
# directories in which files of `outputs` are allowed to be (and not
# in children directories). Generation will fail if an output isn't
# in a directory in the list.
#
# root_dir: Optional root source dir for Python dependencies
# computation. Defaults to "${generator_lib_dir}/..". Any dependency
# outside of this directory is considered a system file and will be
# omitted.
#
template("generator_lib_action") {
_generator_args = []
if (defined(invoker.args)) {
_generator_args += invoker.args
}
assert(defined(invoker.generator_lib_dir),
"generator_lib_dir must be defined before calling this action!")
_template_dir = "${invoker.generator_lib_dir}/templates"
if (defined(invoker.template_dir)) {
_template_dir = invoker.template_dir
}
_generator_args += [
"--template-dir",
rebase_path(_template_dir),
]
if (defined(invoker.root_dir)) {
_generator_args += [
"--root-dir",
rebase_path(_root_dir, root_build_dir),
]
}
if (defined(invoker.jinja2_path)) {
_generator_args += [
"--jinja2-path",
rebase_path(invoker.jinja2_path),
]
}
# Chooses either the default gen_dir or the custom one required by the
# invoker. This allows moving the definition of code generators in different
# BUILD.gn files without changing the location of generated file. Without
# this generated headers could cause issues when old headers aren't removed.
_gen_dir = target_gen_dir
if (defined(invoker.custom_gen_dir)) {
_gen_dir = invoker.custom_gen_dir
}
# For build parallelism GN wants to know the exact inputs and outputs of
# action targets like we use for our code generator. We avoid asking the
# generator about its inputs by using the "depfile" feature of GN/Ninja.
#
# A ninja limitation is that the depfile is a subset of Makefile that can
# contain a single target, so we output a single "JSON-tarball" instead.
_json_tarball = "${_gen_dir}/${target_name}.json_tarball"
_json_tarball_target = "${target_name}__json_tarball"
_json_tarball_depfile = "${_json_tarball}.d"
_generator_args += [
"--output-json-tarball",
rebase_path(_json_tarball, root_build_dir),
"--depfile",
rebase_path(_json_tarball_depfile, root_build_dir),
]
# After the JSON tarball is created we need an action target to extract it
# with a list of its outputs. The invoker provided a list of expected
# outputs. To make sure the list is in sync between the generator and the
# build files, we write it to a file and ask the generator to assert it is
# correct.
_expected_outputs_file = "${_gen_dir}/${target_name}.expected_outputs"
write_file(_expected_outputs_file, invoker.outputs)
_generator_args += [
"--expected-outputs-file",
rebase_path(_expected_outputs_file, root_build_dir),
]
# Check that all of the outputs are in a directory that's allowed. This is
# useful to keep the list of directories in sink with other parts of the
# build.
if (defined(invoker.allowed_output_dirs)) {
_allowed_output_dirs_file = "${_gen_dir}/${target_name}.allowed_output_dirs"
write_file(_allowed_output_dirs_file, invoker.allowed_output_dirs)
_generator_args += [
"--allowed-output-dirs-file",
rebase_path(_allowed_output_dirs_file, root_build_dir),
]
}
# The code generator invocation that will write the JSON tarball, check the
# outputs are what's expected and write a depfile for Ninja.
action(_json_tarball_target) {
script = invoker.script
outputs = [
_json_tarball,
]
depfile = _json_tarball_depfile
args = _generator_args
}
# Extract the JSON tarball into the gen_dir
action(target_name) {
script = "${invoker.generator_lib_dir}/extract_json.py"
args = [
rebase_path(_json_tarball, root_build_dir),
rebase_path(_gen_dir, root_build_dir),
]
deps = [
":${_json_tarball_target}",
]
inputs = [
_json_tarball,
]
# The expected output list is relative to the gen_dir but action
# target outputs are from the root dir so we need to rebase them.
outputs = []
foreach(source, invoker.outputs) {
outputs += [ "${_gen_dir}/${source}" ]
}
}
}