remove use_siso_default.py

use_siso_default.py is no longer needed.
autoninja doesn't use it: https://crrev.com/c/6301272

Bug: 397994249
Change-Id: Iff1154492efe5c40e4a03bf5c220dd15e3c7e598
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6298322
Reviewed-by: Dirk Pranke <dpranke@google.com>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Fumitoshi Ukai <ukai@google.com>
Cr-Commit-Position: refs/heads/main@{#1425547}

build/dotfile_settings.gni

@@ -34,7 +34,6 @@ build_dotfile_settings = {
     "//build/toolchain/concurrent_links.gni",
     "//build/toolchain/nacl/BUILD.gn",
     "//build/toolchain/rbe.gni",
-    "//build/toolchain/siso.gni",
     "//build/toolchain/toolchain.gni",
     "//build/toolchain/win/BUILD.gn",
     "//build/toolchain/win/win_toolchain_data.gni",

build/toolchain/siso.gni

@@ -1,16 +1,8 @@
 # Defines the configuration of siso (next-gen build system)
 
-use_siso_default = false
-if (current_toolchain == default_toolchain) {
-  use_siso_default =
-      exec_script(rebase_path("//build/toolchain/use_siso_default.py"),
-                  [],
-                  "value",
-                  [])
-}
-
 declare_args() {
   # Placeholder to allow having use_siso in args.gn file.
   # Explicit `use_siso` in args.gn can override default.
-  use_siso = use_siso_default
+  # This is used only for autoninja (to dispatch siso or ninja).
+  use_siso = true
 }

build/toolchain/use_reclient_value.py

@@ -11,21 +11,14 @@ or used in depot_tools' autoninja or siso wrapper.
 import os
 import sys
 
-sys.path.insert(0, os.path.join(os.path.dirname(__file__)))
-import use_siso_default
-
 sys.path.insert(0, os.path.join(os.path.dirname(__file__), os.path.pardir))
 import gn_helpers
 
 def use_reclient_value(output_dir):
   """Returns use_reclient value."""
-  use_remoteexec = None
-  use_reclient = None
-  use_siso = use_siso_default.use_siso_default(output_dir)
   args = gn_helpers.ReadArgsGN(output_dir)
   use_remoteexec = args.get('use_remoteexec', False)
   use_reclient = args.get('use_reclient')
-  use_siso = args.get('use_siso', use_siso)
   # If args.gn has use_reclient, use it.
   if use_reclient is not None:
     return use_reclient

build/toolchain/use_siso_default.py

@@ -1,76 +0,0 @@
-#!/usr/bin/env python3
-# Copyright 2024 The Chromium Authors
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-"""Script to decide use_siso default value.
-
-`use_siso_default` is called by siso.gni via exec_script, and
-`use_siso_default_and_suggest_siso` is called by autoninja in depot_tools.
-"""
-# TODO(crbug.com/379584977): move this to depot_tools once `use_siso`
-# is not used for build graph.
-
-import os
-import shutil
-import sys
-
-_SISO_SUGGESTION = """Please run 'gn clean {output_dir}' when convenient to upgrade this output directory to Siso (Chromium’s Ninja replacement). If you run into any issues, please file a bug via go/siso-bug and switch back temporarily by setting the GN arg 'use_siso = false'"""
-
-
-def _is_google_corp_machine():
-  """This assumes that corp machine has gcert binary in known location."""
-  return shutil.which("gcert") is not None
-
-
-def _siso_supported(output_dir):
-  """Returns whether siso is supported for the current scenario."""
-  # If no .sisoenv, use Ninja.
-  if not os.path.exists(
-      os.path.join(os.path.dirname(__file__), "../config/siso/.sisoenv")):
-    return False
-
-  # If it's not chromium project, use Ninja.
-  gclient_args_gni = os.path.join(os.path.dirname(__file__),
-                                  "../config/gclient_args.gni")
-  if not os.path.exists(gclient_args_gni):
-    return False
-
-  with open(gclient_args_gni) as f:
-    if "build_with_chromium = true" not in f.read():
-      return False
-
-  # Use Siso by default for Googlers working on corp machine.
-  if _is_google_corp_machine():
-    return True
-
-  # Otherwise, use Ninja, until we are ready to roll it out
-  # on non-corp machines, too.
-  # TODO(378078715): enable True by default.
-  return False
-
-
-def use_siso_default(output_dir, suggest_siso=False):
-  """Returns use_siso default value."""
-  if not _siso_supported(output_dir):
-      return False
-
-  # This output directory is already using Siso.
-  if os.path.exists(os.path.join(output_dir, ".siso_deps")):
-    return True
-
-  # This output directory is still using Ninja.
-  if os.path.exists(os.path.join(output_dir, ".ninja_deps")):
-    if suggest_siso:
-        print(_SISO_SUGGESTION.format(output_dir=output_dir), file=sys.stderr)
-    return False
-
-  return True
-
-def use_siso_default_and_suggest_siso(output_dir):
-  """Returns use_siso default value and suggests to use siso."""
-  return use_siso_default(output_dir, suggest_siso = True)
-
-
-if __name__ == "__main__":
-  # exec_script runs in output directory.
-  print(str(use_siso_default(".")).lower())