pkg/build_systems.bzl - third_party/protobuf - Git at Google

 # Starlark utilities for working with other build systems

 load("@rules_pkg//:providers.bzl", "PackageFilegroupInfo", "PackageFilesInfo")
 load(":cc_dist_library.bzl", "CcFileList")

 ################################################################################
 # Macro to create CMake and Automake source lists.
 ################################################################################

 def gen_file_lists(name, out_stem, **kwargs):
     gen_cmake_file_lists(
         name = name + "_cmake",
         out = out_stem + ".cmake",
         source_prefix = "${protobuf_SOURCE_DIR}/",
         **kwargs
     )
     native.filegroup(
         name = name,
         srcs = [
             out_stem + ".cmake",
         ],
         visibility = ["//src:__pkg__"],
     )

 ################################################################################
 # Aspect that extracts srcs, hdrs, etc.
 ################################################################################

 ProtoFileList = provider(
     doc = "List of proto files and generated code to be built into a library.",
     fields = {
         # Proto files:
         "proto_srcs": "proto file sources",

         # Generated sources:
         "hdrs": "header files that are expected to be generated",
         "srcs": "source files that are expected to be generated",
     },
 )

 def _flatten_target_files(targets):
     files = []
     for target in targets:
         for tfile in target.files.to_list():
             files.append(tfile)
     return files

 def _file_list_aspect_impl(target, ctx):
     # We're going to reach directly into the attrs on the traversed rule.
     rule_attr = ctx.rule.attr
     providers = []

     # Extract sources from a `proto_library`:
     if ProtoInfo in target:
         proto_srcs = []
         srcs = []
         hdrs = []
         for src in _flatten_target_files(rule_attr.srcs):
             proto_srcs.append(src)
             srcs.append("%s/%s.pb.cc" % (src.dirname, src.basename))
             hdrs.append("%s/%s.pb.h" % (src.dirname, src.basename))

         providers.append(ProtoFileList(
             proto_srcs = proto_srcs,
             srcs = srcs,
             hdrs = hdrs,
         ))

     return providers

 file_list_aspect = aspect(
     doc = """
 Aspect to provide the list of sources and headers from a rule.

 Output is CcFileList and/or ProtoFileList. Example:

   cc_library(
       name = "foo",
       srcs = [
           "foo.cc",
           "foo_internal.h",
       ],
       hdrs = ["foo.h"],
       textual_hdrs = ["foo_inl.inc"],
   )
   # produces:
   # CcFileList(
   #     hdrs = [File("foo.h")],
   #     textual_hdrs = [File("foo_inl.inc")],
   #     internal_hdrs = [File("foo_internal.h")],
   #     srcs = [File("foo.cc")],
   # )

   proto_library(
       name = "bar_proto",
       srcs = ["bar.proto"],
   )
   # produces:
   # ProtoFileList(
   #     proto_srcs = ["bar.proto"],
   #     # Generated filenames are synthesized:
   #     hdrs = ["bar.pb.h"],
   #     srcs = ["bar.pb.cc"],
   # )
 """,
     implementation = _file_list_aspect_impl,
 )

 ################################################################################
 # Generic source lists generation
 #
 # This factory creates a rule implementation that is parameterized by a
 # fragment generator function.
 ################################################################################

 def _create_file_list_impl(ctx, fragment_generator):
     # `fragment_generator` is a function like:
     #     def fn(originating_rule: Label,
     #            varname: str,
     #            source_prefix: str,
     #            path_strings: [str]) -> str
     #
     # It returns a string that defines `varname` to `path_strings`, each
     # prepended with `source_prefix`.
     #
     # When dealing with `File` objects, the `short_path` is used to strip
     # the output prefix for generated files.

     out = ctx.outputs.out

     fragments = []
     for srcrule, libname in ctx.attr.src_libs.items():
         if CcFileList in srcrule:
             cc_file_list = srcrule[CcFileList]

             # Turn depsets of files into sorted lists.
             srcs = sorted(cc_file_list.srcs.to_list())
             hdrs = sorted(
                 depset(transitive = [
                     cc_file_list.textual_hdrs,
                     cc_file_list.hdrs,
                 ]).to_list(),
             )

             fragments.extend([
                 fragment_generator(
                     srcrule.label,
                     libname + "_srcs",
                     ctx.attr.source_prefix,
                     [f.short_path for f in srcs],
                 ),
                 fragment_generator(
                     srcrule.label,
                     libname + "_hdrs",
                     ctx.attr.source_prefix,
                     [f.short_path for f in hdrs],
                 ),
             ])

         if ProtoFileList in srcrule:
             proto_file_list = srcrule[ProtoFileList]
             fragments.extend([
                 fragment_generator(
                     srcrule.label,
                     libname + "_proto_srcs",
                     ctx.attr.source_prefix,
                     [f.short_path for f in proto_file_list.proto_srcs],
                 ),
                 fragment_generator(
                     srcrule.label,
                     libname + "_srcs",
                     ctx.attr.source_prefix,
                     proto_file_list.srcs,
                 ),
                 fragment_generator(
                     srcrule.label,
                     libname + "_hdrs",
                     ctx.attr.source_prefix,
                     proto_file_list.hdrs,
                 ),
             ])

         files = {}

         if PackageFilegroupInfo in srcrule:
             for pkg_files_info, origin in srcrule[PackageFilegroupInfo].pkg_files:
                 # keys are the destination path:
                 files.update(pkg_files_info.dest_src_map)

         if PackageFilesInfo in srcrule:
             # keys are the destination:
             files.update(srcrule[PackageFilesInfo].dest_src_map)

         if files == {} and DefaultInfo in srcrule and CcFileList not in srcrule:
             # This could be an individual file or filegroup.
             # We explicitly ignore rules with CcInfo, since their
             # output artifacts are libraries or binaries.
             files.update(
                 {
                     f.short_path: 1
                     for f in srcrule[DefaultInfo].files.to_list()
                 },
             )

         if files:
             fragments.append(
                 fragment_generator(
                     srcrule.label,
                     libname + "_files",
                     ctx.attr.source_prefix,
                     sorted(files.keys()),
                 ),
             )

     ctx.actions.write(
         output = out,
         content = (ctx.attr._header % ctx.label) + "\n".join(fragments),
     )

     return [DefaultInfo(files = depset([out]))]

 # Common rule attrs for rules that use `_create_file_list_impl`:
 # (note that `_header` is also required)
 _source_list_common_attrs = {
     "out": attr.output(
         doc = (
             "The generated filename. This should usually have a build " +
             "system-specific extension, like `out.am` or `out.cmake`."
         ),
         mandatory = True,
     ),
     "src_libs": attr.label_keyed_string_dict(
         doc = (
             "A dict, {target: libname} of libraries to include. " +
             "Targets can be C++ rules (like `cc_library` or `cc_test`), " +
             "`proto_library` rules, files, `filegroup` rules, `pkg_files` " +
             "rules, or `pkg_filegroup` rules. " +
             "The libname is a string, and used to construct the variable " +
             "name in the `out` file holding the target's sources. " +
             "For generated files, the output root (like `bazel-bin/`) is not " +
             "included. " +
             "For `pkg_files` and `pkg_filegroup` rules, the destination path " +
             "is used."
         ),
         mandatory = True,
         providers = [
             [CcFileList],
             [DefaultInfo],
             [PackageFilegroupInfo],
             [PackageFilesInfo],
             [ProtoFileList],
         ],
         aspects = [file_list_aspect],
     ),
     "source_prefix": attr.string(
         doc = "String to prepend to each source path.",
     ),
 }

 ################################################################################
 # CMake source lists generation
 ################################################################################

 def _cmake_var_fragment(owner, varname, prefix, entries):
     """Returns a single `set(varname ...)` fragment (CMake syntax).

     Args:
       owner: Label, the rule that owns these srcs.
       varname: str, the var name to set.
       prefix: str, prefix to prepend to each of `entries`.
       entries: [str], the entries in the list.

     Returns:
       A string.
     """
     return (
         "# {owner}\n" +
         "set({varname}\n" +
         "{entries}\n" +
         ")\n"
     ).format(
         owner = owner,
         varname = varname,
         # Strip out "wkt/google/protobuf/" from the well-known type file paths.
         # This is currently necessary to allow checked-in and generated
         # versions of the well-known type generated code to coexist.
         entries = "\n".join(["  %s%s" % (prefix, f.replace("wkt/google/protobuf/", "")) for f in entries]),
     )

 def _cmake_file_list_impl(ctx):
     _create_file_list_impl(ctx, _cmake_var_fragment)

 gen_cmake_file_lists = rule(
     doc = """
 Generates a CMake-syntax file with lists of files.

 The generated file defines variables with lists of files from `srcs`. The
 intent is for these files to be included from a non-generated CMake file
 which actually defines the libraries based on these lists.

 For C++ rules, the following are generated:
     {libname}_srcs: contains srcs.
     {libname}_hdrs: contains hdrs and textual_hdrs.

 For proto_library, the following are generated:
     {libname}_proto_srcs: contains the srcs from the `proto_library` rule.
     {libname}_srcs: contains syntesized paths for generated C++ sources.
     {libname}_hdrs: contains syntesized paths for generated C++ headers.

 """,
     implementation = _cmake_file_list_impl,
     attrs = dict(
         _source_list_common_attrs,
         _header = attr.string(
             default = """\
 # Auto-generated by %s
 #
 # This file contains lists of sources based on Bazel rules. It should
 # be included from a hand-written CMake file that defines targets.
 #
 # Changes to this file will be overwritten based on Bazel definitions.

 if(${CMAKE_VERSION} VERSION_GREATER 3.10 OR ${CMAKE_VERSION} VERSION_EQUAL 3.10)
   include_guard()
 endif()

 """,
         ),
     ),
 )
	# Starlark utilities for working with other build systems

	load("@rules_pkg//:providers.bzl", "PackageFilegroupInfo", "PackageFilesInfo")
	load(":cc_dist_library.bzl", "CcFileList")

	################################################################################
	# Macro to create CMake and Automake source lists.
	################################################################################

	def gen_file_lists(name, out_stem, **kwargs):
	gen_cmake_file_lists(
	name = name + "_cmake",
	out = out_stem + ".cmake",
	source_prefix = "${protobuf_SOURCE_DIR}/",
	**kwargs
	)
	native.filegroup(
	name = name,
	srcs = [
	out_stem + ".cmake",
	],
	visibility = ["//src:__pkg__"],
	)

	################################################################################
	# Aspect that extracts srcs, hdrs, etc.
	################################################################################

	ProtoFileList = provider(
	doc = "List of proto files and generated code to be built into a library.",
	fields = {
	# Proto files:
	"proto_srcs": "proto file sources",

	# Generated sources:
	"hdrs": "header files that are expected to be generated",
	"srcs": "source files that are expected to be generated",
	},
	)

	def _flatten_target_files(targets):
	files = []
	for target in targets:
	for tfile in target.files.to_list():
	files.append(tfile)
	return files

	def _file_list_aspect_impl(target, ctx):
	# We're going to reach directly into the attrs on the traversed rule.
	rule_attr = ctx.rule.attr
	providers = []

	# Extract sources from a `proto_library`:
	if ProtoInfo in target:
	proto_srcs = []
	srcs = []
	hdrs = []
	for src in _flatten_target_files(rule_attr.srcs):
	proto_srcs.append(src)
	srcs.append("%s/%s.pb.cc" % (src.dirname, src.basename))
	hdrs.append("%s/%s.pb.h" % (src.dirname, src.basename))

	providers.append(ProtoFileList(
	proto_srcs = proto_srcs,
	srcs = srcs,
	hdrs = hdrs,
	))

	return providers

	file_list_aspect = aspect(
	doc = """
	Aspect to provide the list of sources and headers from a rule.

	Output is CcFileList and/or ProtoFileList. Example:

	cc_library(
	name = "foo",
	srcs = [
	"foo.cc",
	"foo_internal.h",
	],
	hdrs = ["foo.h"],
	textual_hdrs = ["foo_inl.inc"],
	)
	# produces:
	# CcFileList(
	# hdrs = [File("foo.h")],
	# textual_hdrs = [File("foo_inl.inc")],
	# internal_hdrs = [File("foo_internal.h")],
	# srcs = [File("foo.cc")],
	# )

	proto_library(
	name = "bar_proto",
	srcs = ["bar.proto"],
	)
	# produces:
	# ProtoFileList(
	# proto_srcs = ["bar.proto"],
	# # Generated filenames are synthesized:
	# hdrs = ["bar.pb.h"],
	# srcs = ["bar.pb.cc"],
	# )
	""",
	implementation = _file_list_aspect_impl,
	)

	################################################################################
	# Generic source lists generation
	#
	# This factory creates a rule implementation that is parameterized by a
	# fragment generator function.
	################################################################################

	def _create_file_list_impl(ctx, fragment_generator):
	# `fragment_generator` is a function like:
	# def fn(originating_rule: Label,
	# varname: str,
	# source_prefix: str,
	# path_strings: [str]) -> str
	#
	# It returns a string that defines `varname` to `path_strings`, each
	# prepended with `source_prefix`.
	#
	# When dealing with `File` objects, the `short_path` is used to strip
	# the output prefix for generated files.

	out = ctx.outputs.out

	fragments = []
	for srcrule, libname in ctx.attr.src_libs.items():
	if CcFileList in srcrule:
	cc_file_list = srcrule[CcFileList]

	# Turn depsets of files into sorted lists.
	srcs = sorted(cc_file_list.srcs.to_list())
	hdrs = sorted(
	depset(transitive = [
	cc_file_list.textual_hdrs,
	cc_file_list.hdrs,
	]).to_list(),
	)

	fragments.extend([
	fragment_generator(
	srcrule.label,
	libname + "_srcs",
	ctx.attr.source_prefix,
	[f.short_path for f in srcs],
	),
	fragment_generator(
	srcrule.label,
	libname + "_hdrs",
	ctx.attr.source_prefix,
	[f.short_path for f in hdrs],
	),
	])

	if ProtoFileList in srcrule:
	proto_file_list = srcrule[ProtoFileList]
	fragments.extend([
	fragment_generator(
	srcrule.label,
	libname + "_proto_srcs",
	ctx.attr.source_prefix,
	[f.short_path for f in proto_file_list.proto_srcs],
	),
	fragment_generator(
	srcrule.label,
	libname + "_srcs",
	ctx.attr.source_prefix,
	proto_file_list.srcs,
	),
	fragment_generator(
	srcrule.label,
	libname + "_hdrs",
	ctx.attr.source_prefix,
	proto_file_list.hdrs,
	),
	])

	files = {}

	if PackageFilegroupInfo in srcrule:
	for pkg_files_info, origin in srcrule[PackageFilegroupInfo].pkg_files:
	# keys are the destination path:
	files.update(pkg_files_info.dest_src_map)

	if PackageFilesInfo in srcrule:
	# keys are the destination:
	files.update(srcrule[PackageFilesInfo].dest_src_map)

	if files == {} and DefaultInfo in srcrule and CcFileList not in srcrule:
	# This could be an individual file or filegroup.
	# We explicitly ignore rules with CcInfo, since their
	# output artifacts are libraries or binaries.
	files.update(
	{
	f.short_path: 1
	for f in srcrule[DefaultInfo].files.to_list()
	},
	)

	if files:
	fragments.append(
	fragment_generator(
	srcrule.label,
	libname + "_files",
	ctx.attr.source_prefix,
	sorted(files.keys()),
	),
	)

	ctx.actions.write(
	output = out,
	content = (ctx.attr._header % ctx.label) + "\n".join(fragments),
	)

	return [DefaultInfo(files = depset([out]))]

	# Common rule attrs for rules that use `_create_file_list_impl`:
	# (note that `_header` is also required)
	_source_list_common_attrs = {
	"out": attr.output(
	doc = (
	"The generated filename. This should usually have a build " +
	"system-specific extension, like `out.am` or `out.cmake`."
	),
	mandatory = True,
	),
	"src_libs": attr.label_keyed_string_dict(
	doc = (
	"A dict, {target: libname} of libraries to include. " +
	"Targets can be C++ rules (like `cc_library` or `cc_test`), " +
	"`proto_library` rules, files, `filegroup` rules, `pkg_files` " +
	"rules, or `pkg_filegroup` rules. " +
	"The libname is a string, and used to construct the variable " +
	"name in the `out` file holding the target's sources. " +
	"For generated files, the output root (like `bazel-bin/`) is not " +
	"included. " +
	"For `pkg_files` and `pkg_filegroup` rules, the destination path " +
	"is used."
	),
	mandatory = True,
	providers = [
	[CcFileList],
	[DefaultInfo],
	[PackageFilegroupInfo],
	[PackageFilesInfo],
	[ProtoFileList],
	],
	aspects = [file_list_aspect],
	),
	"source_prefix": attr.string(
	doc = "String to prepend to each source path.",
	),
	}

	################################################################################
	# CMake source lists generation
	################################################################################

	def _cmake_var_fragment(owner, varname, prefix, entries):
	"""Returns a single `set(varname ...)` fragment (CMake syntax).

	Args:
	owner: Label, the rule that owns these srcs.
	varname: str, the var name to set.
	prefix: str, prefix to prepend to each of `entries`.
	entries: [str], the entries in the list.

	Returns:
	A string.
	"""
	return (
	"# {owner}\n" +
	"set({varname}\n" +
	"{entries}\n" +
	")\n"
	).format(
	owner = owner,
	varname = varname,
	# Strip out "wkt/google/protobuf/" from the well-known type file paths.
	# This is currently necessary to allow checked-in and generated
	# versions of the well-known type generated code to coexist.
	entries = "\n".join([" %s%s" % (prefix, f.replace("wkt/google/protobuf/", "")) for f in entries]),
	)

	def _cmake_file_list_impl(ctx):
	_create_file_list_impl(ctx, _cmake_var_fragment)

	gen_cmake_file_lists = rule(
	doc = """
	Generates a CMake-syntax file with lists of files.

	The generated file defines variables with lists of files from `srcs`. The
	intent is for these files to be included from a non-generated CMake file
	which actually defines the libraries based on these lists.

	For C++ rules, the following are generated:
	{libname}_srcs: contains srcs.
	{libname}_hdrs: contains hdrs and textual_hdrs.

	For proto_library, the following are generated:
	{libname}_proto_srcs: contains the srcs from the `proto_library` rule.
	{libname}_srcs: contains syntesized paths for generated C++ sources.
	{libname}_hdrs: contains syntesized paths for generated C++ headers.

	""",
	implementation = _cmake_file_list_impl,
	attrs = dict(
	_source_list_common_attrs,
	_header = attr.string(
	default = """\
	# Auto-generated by %s
	#
	# This file contains lists of sources based on Bazel rules. It should
	# be included from a hand-written CMake file that defines targets.
	#
	# Changes to this file will be overwritten based on Bazel definitions.

	if(${CMAKE_VERSION} VERSION_GREATER 3.10 OR ${CMAKE_VERSION} VERSION_EQUAL 3.10)
	include_guard()
	endif()

	""",
	),
	),
	)