tree ec3edfa1469d801a0656c60275dfeca40475a0ec
parent eaebec13127c17304ede6b9553fdbe327848fd3b
author Jingwen Chen <jingwen@google.com> 1596809794 +0000
committer Jingwen Chen <jingwen@google.com> 1598010346 +0000

Surface module properties as Bazel BUILD target attributes in the Bazel overlay

This patchset changes bazel_overlay to generate soong_module as a macro,
instead of a rule, and generate module properties in the BUILD files as
kwargs to the soong_module macro.

Here's a sample of the new BUILD files with module properties:

bionic/libdl/BUILD.bazel:
https://paste.googleplex.com/6484466996346880?raw

art/build/apex/BUILD.bazel:
https://paste.googleplex.com/5461276001042432?raw

bionic/apex/BUILD.bazel:
https://paste.googleplex.com/4932795173437440?raw

soong_module is now a macro that conditionally expands to underlying
soong_<module type> rules with statically defined attributes. In this
CL, we are starting with a hardcoded filegroup rule definition to
demonstrate the conditional rule loading within the soong_module macro.
If the module_type matches an existing Bazel rule, soong_module forwards
the entire **kwargs into the rule, which Bazel typechecks.

Non-filegroup module types will be expanded into generic_soong_module,
but with the kwargs dropped.

This approach allows us to:

1) Programmtically generate soong_<module type> rules for all module
types available in Soong, together with the statically defined attribute
types in `attrs`.
2) Incrementally migrate and test individual module types from
generic_soong_module to their module rule shims.
3) Swap out the module rule shims to the actual Bazel rules (e.g
cc_library, java_library) and perform attribute manipulation in Starlark
itself.

Example of querying against the 'srcs' attribute in soong_filegroup:

```
$ bazel cquery 'kind(soong_filegroup, //...)' | wc -l
590

$ bazel cquery --output=build 'attr(srcs, "linker.cpp",
kind(soong_filegroup, //bionic/...))'
INFO: Analyzed 3907 targets (0 packages loaded, 0 targets configured).
INFO: Found 3907 targets...
/usr/local/google/home/jingwen/aosp/out/soong/bazel_overlay/bionic/linker/BUILD.bazel:4144:13
soong_filegroup(
  name = "linker_sources",
  generator_name = "linker_sources",
  generator_function = "soong_module",
  generator_location = "bionic/linker/BUILD.bazel:4144:13",
  srcs = ["dlfcn.cpp", "linker.cpp", "linker_block_allocator.cpp",
"linker_dlwarning.cpp", "linker_cfi.cpp", "linker_config.cpp",
"linker_debug.cpp", "linker_gdb_support.cpp", "linker_globals.cpp",
"linker_libc_support.c", "linker_libcxx_support.cpp",
"linker_namespaces.cpp", "linker_logger.cpp",
"linker_mapped_file_fragment.cpp", "linker_phdr.cpp",
"linker_relocate.cpp", "linker_sdk_versions.cpp", "linker_soinfo.cpp",
"linker_tls.cpp", "linker_utils.cpp", "rt.cpp"],
  deps = [],
)
/usr/local/google/home/jingwen/aosp/out/soong/bazel_overlay/soong_module.bzl:32:23
in <toplevel>
```

This CL is known to be lacking the following features, and will be looked at in follow up CLs:

1) Pretty printing reflect.Interface properties, like arch, multilib and
dists.
2) Generating module Bazel rule shims for all module types, instead of
hardcoding them like `soong_filegroup`.

Bug: 162720644
Test: bazel_overlay_test.go (soong build test)
Test: m bazel_overlay && cd out/soong/bazel_overlay && bazel cquery //...
Signed-off-by: Jingwen Chen <jingwen@google.com>
Change-Id: Ic1e448887eb540ed15a55bc4090cf75a4d832d41