# Copyright 2018 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import("//build/rust/rustc_artifact.gni")
import("//build/rust/rustc_test.gni")
import("//build/toolchain/rbe.gni")

# Defines a Rust binary
#
# Parameters
#
#   output_name (optional)
#     Name of the output file. Also used as the crate name of the binary,
#     except the crate name has dashes replaced with underscores. If not
#     specified, it defaults to the target name.
#
#   name (optional, deprecated)
#     Deprecated version of output_name.
#
#   output_dir (optional)
#     Directory that the resulting binary should be placed in.
#     See: `gn help output_dir`
#
#   output_extension (optional)
#     The file extension for the binary.
#     See: `gn help output_extension`
#
#   version (optional)
#     Semver version of the crate as seen on crates.io.
#
#   edition
#     Edition of the Rust language to be used. See
#     https://doc.rust-lang.org/edition-guide/editions/index.html for more info on rust editions.
#
#   configs (optional)
#     A list of config labels applying to this target.
#
#   enforce_source_listing (optional)
#     When true, enforces that any source files used by the Rust compiler are
#     listed in `sources`. Defaults to true.
#
#   sources (optional)
#     List of source files which this crate is allowed to compile. Only
#     allowed when `enforce_source_listing = true`.
#     The Rust compiler discovers source files by following `mod` declarations
#     starting at the `source_root`. The discovered source files must match this
#     list.
#
#   inputs (optional)
#     List of additional non-source files read by the compiler. These are typically
#     configuration or test-data files included in the build with the `include_str!`
#     macro. Only allowed when `enforce_source_listing = true`.
#
#   deps (optional)
#     List of rust_library GN targets on which this crate depends.
#     Third party crates can be included through paths like
#     "//third_party/rust_crates:<cratename>",
#
#   test_deps (optional)
#     List of rust_library GN targets on which this crate's tests depend.
#
#   non_rust_deps (optional)
#     List of non-rust_library GN targets on which this crate depends.
#     Obsolete. Please use deps instead.
#
#   data_deps (optional)
#     List of GN targets that are only needed at runtime.
#
#   with_unit_tests (optional)
#     Builds unit tests associated with the binary. This will create a
#     `<output_name_underscored>_bin_test` test file in the output directory,
#     and a new GN target called <name>_test.
#     Equivalent to adding a `rustc_test` target with that name and the same
#     source_root.
#
#   test_args (optional)
#     List of flags to pass directly to the test binary, e.g.
#     ["--nocapture"].
#
#   test_environments (optional)
#     What environments unit tests, if provided, should target. Only used here
#     for linux and mac tests, with a default value of a general linux/mac
#     environment (as a function of $current_os).
#     See environments parameter //build/testing/test_spec.gni for more
#     details.
#
#   sdk_category (optional)
#     If this field is set, this rust binary will be included in SDK builds for
#     the provided category. See //build/sdk/sdk_atom.gni for available
#     categories.
#
#   source_root (optional)
#     Location of the crate root (e.g. `src/main.rs` or `src/lib.rs`).
#     This defaults to `./src/main.rs` for binaries and `./src/lib.rs` for libraries,
#     and should only be changed when absolutely necessary
#     (such as in the case of generated code).
#
#   features (optional)
#     A list of conditional compilation flags to enable. This can be used to set features for crates
#     built in-tree which are also published to crates.io. This would be passed to rustc as
#     '--cfg feature="XXX"'
#
#   rustenv (optional)
#     A list of environment variables that will be set when running the rust
#     compiler. These can be accessed at compile time with
#     [`std::env!`](https://doc.rust-lang.org/stable/std/macro.env.html)
#
#   disable_rbe (optional)
#     Set to true to force this target to build locally, overriding the global
#     `rust_rbe_enable`.  This applies to the unit-test as well, unless
#     `test_disable_rbe` is specified.
#
#   test_disable_rbe (optional)
#     Set to true to build only the unit-test locally.
#
#   disable_clippy (optional)
#     Don't run clippy on this target.
#
#   quiet_clippy (boolean, optional)
#     Passed through to rustc_artifact(), see that template for documentation.
#
#   disable_rustdoc (optional)
#     Don't add this target to https://fuchsia.dev/go/rustdoc
#     NOTE: for binaries this is enabled by default
#
#   original_target_name (optional)
#     The name of the target as it appears in the BUILD file. Enables tooling
#     to find the template invocation in a BUILD file where this target was defined.
#
#   exclude_toolchain_tags (optional)
#     List of toolchain or variant tags to exclude this target from. This can be
#     useful if the target is incompatible with a certain toolchain or variant.
#     See build/toolchain/toolchain_tags.gni and build/toolchain/variant_tags.gni
#     for a list of common tags.
#
#   link_args (optional)
#     List of arguments to pass to the linker via "-Clink-args=...".
#
#   assert_no_deps (optional)
#     Ensure no deps on these targets, see [assert_no_deps](https://gn.googlesource.com/gn/+/main/docs/reference.md#var_assert_no_deps)

# Example of usage:
#
#   rustc_binary("foo-bar") {
#     deps = [
#       "//garnet/public/rust/bar",
#       "//third_party/rust_crates:argh",
#       "//third_party/rust_crates:serde",
#       "//third_party/rust_crates:slab",
#     ]
#     with_unit_tests = true
#     sources = [ "src/main.rs" ]
#   }
#
# Example of using the outputs of the above:
#
#   package("foo") {
#     deps = [
#       ":foo-bar",
#     ]
#
#     binaries = [
#       {
#         name = "foo_bar"
#         dest = "foo-bar"
#       }
#    }
#
#   test_package("foo-bar-tests") {
#     deps = [
#       ":foo-bar_test",
#     ]
#
#    tests = [
#      {
#        name = "foo_bar_bin_test"
#      }
#    ]
#
template("rustc_binary") {
  not_needed(invoker, [ "version" ])

  # If I delete this block, GN complains about pool being unused,
  # even though the generated ninja files look correct.
  if (defined(invoker.pool)) {
    assert(invoker.pool != "")
  }

  if (defined(invoker.original_target_name)) {
    _original_target_name = invoker.original_target_name
  } else {
    _original_target_name = target_name
  }

  # use the target name unless another name is specified
  assert(!(defined(invoker.output_name) && defined(invoker.name)),
         "Only one of output_name and name may be specified.")
  _output_name = target_name
  if (defined(invoker.output_name)) {
    _output_name = invoker.output_name
  } else if (defined(invoker.name)) {
    _output_name = invoker.name
  }

  # rustc does not support dashes in crate names
  _crate_name = string_replace(_output_name, "-", "_")

  # if "with_unit_tests" is set to true, generate an additional rust test target
  # TODO(https://fxbug.dev/42152447): accept a string.
  if (defined(invoker.with_unit_tests) && invoker.with_unit_tests) {
    rustc_test_internal("${target_name}_test") {
      output_name = "${_output_name}_bin_test"
      original_target_name = _original_target_name

      if (defined(invoker.test_args)) {
        args = invoker.test_args
      }

      configs = []
      configs = invoker.configs

      # rustc_test defaults to assuming the input is a binary.
      # specify the source_root here to avoid this.
      source_root = "src/main.rs"
      if (defined(invoker.source_root)) {
        source_root = invoker.source_root
      }
      forward_variables_from(invoker,
                             "*",
                             [
                               "name",
                               "disable_rustdoc",
                               "assert_no_deps",
                               "link_args",
                               "output_name",
                               "source_root",
                               "test_disable_rbe",
                             ])
      if (defined(invoker.test_disable_rbe)) {
        disable_rbe = invoker.test_disable_rbe
      }
    }
  }

  ### Shim that converts rustc_binary to a default GN executable pattern ###

  # default location for rust binaries
  source_root = "src/main.rs"
  if (defined(invoker.source_root)) {
    source_root = invoker.source_root
  }

  rustc_artifact(target_name) {
    target_type = "executable"
    crate_root = source_root
    clippy_crate_type = "bin"
    crate_name = _crate_name
    original_target_name = _original_target_name

    pass_through = {
      # pass through these variables unmodified
      forward_variables_from(invoker,
                             [
                               "data_deps",
                               "exclude_toolchain_tags",
                               "output_dir",
                               "output_extension",
                             ])
      output_name = _output_name
    }

    forward_variables_from(invoker,
                           [
                             "assert_no_deps",
                             "disable_clippy",
                             "quiet_clippy",
                             "edition",
                             "enforce_source_listing",
                             "features",
                             "inputs",
                             "link_args",
                             "pool",
                             "rustenv",
                             "sources",
                             "testonly",
                             "visibility",
                           ])

    disable_rbe = !rust_rbe_enable
    if (defined(invoker.disable_rbe)) {
      disable_rbe = invoker.disable_rbe
    }

    configs = []
    configs = invoker.configs

    # Unstripped binaries can be massive compared to stripped binaries.
    # When skipping downloads, artifacts can be retrieved from RBE later using
    # `build/rbe/dlwrap.py --download ...`.
    if (!disable_rbe && !rust_rbe_download_unstripped_binaries) {
      configs += [ "//build/config/rust:no_download" ]
    }

    deps = []
    if (defined(invoker.deps)) {
      deps += invoker.deps
    }

    # TODO(https://fxbug.dev/42120123) remove "non_rust_deps" as a concept
    if (defined(invoker.non_rust_deps)) {
      deps += invoker.non_rust_deps
    }

    metadata = {
      if (defined(invoker.disable_rustdoc)) {
        disable_rustdoc = [ invoker.disable_rustdoc ]
      } else {
        disable_rustdoc = [ true ]
      }
    }
  }
}