# Starlark utilities for working with other build systems
load("@rules_pkg//:providers.bzl", "PackageFilegroupInfo", "PackageFilesInfo")
################################################################################
# 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 = "${protobuf_SOURCE_DIR}/",
**kwargs
)
gen_automake_file_lists(
name = name + "_automake",
out = out_stem + ".am",
source_prefix = "$(top_srcdir)/",
**kwargs
)
native.filegroup(
name = name,
srcs = [
out_stem + ".cmake",
out_stem + ".am",
],
)
################################################################################
# Aspect that extracts srcs, hdrs, etc.
################################################################################
CcFileList = provider(
doc = "List of files to be built into a library.",
fields = {
# As a rule of thumb, `hdrs` and `textual_hdrs` are the files that
# would be installed along with a prebuilt library.
"hdrs": "public header files, including those used by generated code",
"textual_hdrs": "files which are included but are not self-contained",
# The `internal_hdrs` are header files which appear in `srcs`.
# These are only used when compiling the library.
"internal_hdrs": "internal header files (only used to build .cc files)",
"srcs": "source files",
},
)
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 _combine_cc_file_lists(file_lists):
hdrs = {}
textual_hdrs = {}
internal_hdrs = {}
srcs = {}
for file_list in file_lists:
hdrs.update({f: 1 for f in file_list.hdrs})
textual_hdrs.update({f: 1 for f in file_list.textual_hdrs})
internal_hdrs.update({f: 1 for f in file_list.internal_hdrs})
srcs.update({f: 1 for f in file_list.srcs})
return CcFileList(
hdrs = sorted(hdrs.keys()),
textual_hdrs = sorted(textual_hdrs.keys()),
internal_hdrs = sorted(internal_hdrs.keys()),
srcs = sorted(srcs.keys()),
)
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 `cc_library` (or similar):
if CcInfo in target:
# CcInfo is a proxy for what we expect this rule to look like.
# However, some deps may expose `CcInfo` without having `srcs`,
# `hdrs`, etc., so we use `getattr` to handle that gracefully.
internal_hdrs = []
srcs = []
# Filter `srcs` so it only contains source files. Headers will go
# into `internal_headers`.
for src in _flatten_target_files(getattr(rule_attr, "srcs", [])):
if src.extension.lower() in ["c", "cc", "cpp", "cxx"]:
srcs.append(src)
else:
internal_hdrs.append(src)
providers.append(CcFileList(
hdrs = _flatten_target_files(getattr(rule_attr, "hdrs", [])),
textual_hdrs = _flatten_target_files(getattr(
rule_attr,
"textual_hdrs",
[],
)),
internal_hdrs = internal_hdrs,
srcs = srcs,
))
# 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(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.
def _impl(ctx):
out = ctx.outputs.out
fragments = []
for srcrule, libname in ctx.attr.src_libs.items():
if CcFileList in srcrule:
cc_file_list = srcrule[CcFileList]
fragments.extend([
fragment_generator(
srcrule.label,
libname + "_srcs",
ctx.attr.source_prefix,
[f.short_path for f in cc_file_list.srcs],
),
fragment_generator(
srcrule.label,
libname + "_hdrs",
ctx.attr.source_prefix,
[f.short_path for f in (cc_file_list.hdrs +
cc_file_list.textual_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 CcInfo 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]))]
return _impl
# 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,
entries = "\n".join([" %s%s" % (prefix, f) for f in entries]),
)
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 = _create_file_list_impl(_cmake_var_fragment),
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()
""",
),
),
)
################################################################################
# Automake source lists generation
################################################################################
def _automake_var_fragment(owner, varname, prefix, entries):
"""Returns a single variable assignment fragment (Automake 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.
"""
if len(entries) == 0:
# A backslash followed by a blank line is illegal. We still want
# to emit the variable, though.
return "# {owner}\n{varname} =\n".format(
owner = owner,
varname = varname,
)
fragment = (
"# {owner}\n" +
"{varname} = \\\n" +
"{entries}"
).format(
owner = owner,
varname = varname,
entries = " \\\n".join([" %s%s" % (prefix, f) for f in entries]),
)
return fragment.rstrip("\\ ") + "\n"
gen_automake_file_lists = rule(
doc = """
Generates an Automake-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 Makefile.am
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 = _create_file_list_impl(_automake_var_fragment),
attrs = dict(
_source_list_common_attrs.items(),
_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 Makefile.am that defines targets.
#
# Changes to this file will be overwritten based on Bazel definitions.
""",
),
),
)
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