devtools_entrypoint.gni

# Copyright 2021 The Chromium 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/toolchain/rbe.gni")
import("../../../third_party/typescript/typescript.gni")
import("./copy.gni")
import("./node.gni")
import("./rollup.gni")
import("./vars.gni")

# This defines an entrypoint for DevTools, which uses Rollup
# in release mode, but creates an unbundled JavaScript file
# in debug mode. This entrypoint should only be used if:
# 1. it defines a file that is statically imported. E.g. in
#    the form of "../entrypoint/entrypoint.js".
# 2. it defines a file that is dynamically imported by the
#    runtime. This uses the same notation, but uses a dynamic
#    import in `core/root/Runtime.js`.
template("devtools_entrypoint") {
  assert(defined(invoker.entrypoint),
         "You must define the 'entrypoint' for a rollup target")

  _entrypoint_target_name = "devtools_entrypoint-" + target_name

  _entrypoint_output_file_name = get_path_info(invoker.entrypoint, "name")
  _entrypoint_gen_file_location =
      "$target_gen_dir/$_entrypoint_output_file_name.js"

  _devtools_entrypoint_deps = []

  _is_web_worker = defined(invoker.is_web_worker) && invoker.is_web_worker

  # In debug mode, the entrypoint is kept as-is. This means we only
  # need to compile with TypeScript, which means it will fetch all
  # of its files as separate network requests.
  if (is_debug) {
    _ts_library_target_name = _entrypoint_target_name + "-typescript"

    ts_library(_ts_library_target_name) {
      sources = [ invoker.entrypoint ]

      inputs = invoker.inputs
      deps = invoker.deps

      is_web_worker = _is_web_worker
    }

    _devtools_entrypoint_deps += [ ":$_ts_library_target_name" ]
  } else {
    # In release mode, we are running Rollup and thus bundle all
    # files in the (sub-)folder(s) into 1 file.
    #
    # To make sure that the build system can handle the Rollup
    # bundle, we have to use several tasks. That's because we
    # can't have 2 tasks generate a file to the same location.
    #
    # First, we need to compile the entrypoint with TypeScript
    # as usual. However, we can't put the output into the
    # location of the entrypoint, as that's where we are going
    # to put the Rollup bundle output. Therefore, we need to
    # create a separate file called the "entrypoint.prebundle.ts"
    # file.
    #
    # We compile the "prebundle.ts" with TypeScript, to create
    # the "prebundle.js" file. We pass in the "prebundle.js"
    # into Rollup, which then outputs into the normal
    # "entrypoint.js" location.
    #
    # Since TypeScript does not support renaming of files during
    # compilation, we first have a "copy" task that copies (and
    # essentially renames) the file to the output directory.
    #
    # Additionally, we need to fix the tsconfig renaming, to patch
    # up the generated tsconfig.json as part of the second ts_library
    # step.
    #
    # Since all of these tasks depend on each other, we have to
    # make sure that the GN dependency graph correctly corresponds
    # to that. Therefore, the graph looks like so:
    #
    #   copy -> ts_library -> fix-tsconfig -> rollup
    #
    _entrypoint_output_file_name = get_path_info(invoker.entrypoint, "name")
    _output_file_name =
        "$target_gen_dir/$_entrypoint_output_file_name.prebundle"
    _copy_output_file_name = "$_output_file_name.ts"
    _prebundle_output_file_name = "$_output_file_name.js"

    _copy_target_name = _entrypoint_target_name + "-copy"
    _rollup_target_name = _entrypoint_target_name + "-rollup"
    _prebundle_target_name = _entrypoint_target_name + "-tsconfig"
    _generated_declaration_target_name =
        _entrypoint_target_name + "-generate-declaration"

    node_action(_copy_target_name) {
      script = "scripts/build/ninja/copy-file.js"

      inputs = [ invoker.entrypoint ]

      outputs = [ _copy_output_file_name ]

      _copy_src = rebase_path(".", root_build_dir) + "/" + invoker.entrypoint
      _copy_dest = rebase_path(_copy_output_file_name, root_build_dir)

      args = [
        _copy_src,
        _copy_dest,
      ]

      public_deps = invoker.deps
    }

    ts_library(_prebundle_target_name) {
      sources = [ _copy_output_file_name ]

      rootdir = target_gen_dir

      inputs = invoker.inputs
      deps = invoker.deps

      public_deps = [ ":$_copy_target_name" ]

      is_web_worker = _is_web_worker

      if (defined(use_rbe) && use_rbe && defined(devtools_use_rbe) &&
          devtools_use_rbe) {
        use_rbe = false
      }
    }

    rollup(_rollup_target_name) {
      entrypoint = _prebundle_output_file_name

      output_file_location = _entrypoint_gen_file_location

      # Since rollup bundles both the entrypoint and the files it imports,
      # we have to make sure that, when you change a file it imports, we
      # retrigger Rollup. Since the `invoker.deps` is a reference to the
      # `ts_library` that compiles all of the files it imports, we have to
      # explicitly add it here. If you don't, then the file change will
      # retrigger the copy action above, but "the output of the copy action"
      # is the same. So Ninja will detect that no output has changed for
      # "_typescript_target_name" and bail out. This would then *also* skip
      # the Rollup action.
      public_deps = [ ":$_prebundle_target_name" ] + invoker.deps
    }

    # TypeScript requires a `module.d.ts` that describes
    # the public API of the `module.js` entrypoint. To do so, we copy
    # the generated `prebundle.d.ts` over, as the public API for a
    # rolled up bundle remains the same.
    node_action(_generated_declaration_target_name) {
      script = "scripts/build/ninja/generate-declaration.js"

      args = [
        rebase_path(target_gen_dir, root_build_dir),
        invoker.entrypoint,
      ]

      public_deps = [
        ":$_prebundle_target_name",
        ":$_rollup_target_name",
      ]

      outputs = [ "$target_gen_dir/$_entrypoint_output_file_name.d.ts" ]
    }

    _devtools_entrypoint_deps += [ ":$_generated_declaration_target_name" ]
  }

  # Because we change the filename before rolling up the bundle,
  # tsc can get upset when it uses the original `target_name` to
  # reference a different `ts_library`. The `ts_library` action
  # above generates a `tsconfig.json` which does not include the
  # `target_name`, but instead uses `_ts_library_target_name`.
  #
  # For example, if the `target_name` is "module", the `ts_library`
  # action above generates a
  # `devtools_entrypoint-module-typescript-tsconfig.json`. However,
  # if a different `ts_library` depends on this `devtools_entrypoint`,
  # it depends on it as "../module:module". Therefore, the expected
  # location of the `tsconfig.json` is instead `module-tsconfig.json`.
  #
  # Therefore, we need to generate a separate tsconfig.json which
  # artificially mimics what `ts_library` would have generated.
  _generated_tsconfig_location =
      target_gen_dir + "/" + invoker.target_name + "-tsconfig.json"
  _target_outputs = [ _entrypoint_gen_file_location ]

  node_action(target_name) {
    script = "scripts/build/ninja/generate-tsconfig.js"

    args = [
             rebase_path(_generated_tsconfig_location, root_build_dir),
             rebase_path(invoker.entrypoint, root_build_dir),
           ] + invoker.deps

    public_deps = _devtools_entrypoint_deps

    outputs = [ _generated_tsconfig_location ]

    data = _target_outputs

    metadata = {
      grd_files = _target_outputs
    }

    if (defined(invoker.visibility)) {
      visibility = invoker.visibility
    } else {
      visibility = [ ":*" ]
    }
  }
}

set_defaults("devtools_entrypoint") {
  inputs = []
}