From 9276dc1ff1673152e2bd38b0aabb79313b136555 Mon Sep 17 00:00:00 2001
From: Chris Bracken <chris@bracken.jp>
Date: Tue, 10 May 2022 07:02:35 -0700
Subject: [PATCH] [gn] Extract target_os, target_cpu resolution
 (flutter/engine#33224)

This is a minor refactoring to extract functions that resolve target_os
and target_cpu gn settings.

This is cleanup prior to adding support for host builds on Apple Silicon
Macs.

Issue: https://github.com/flutter/flutter/issues/96745
---
 engine/src/flutter/tools/gn | 76 ++++++++++++++++++-------------------
 1 file changed, 38 insertions(+), 38 deletions(-)

diff --git a/engine/src/flutter/tools/gn b/engine/src/flutter/tools/gn
index 11d7cf63323..8db9728ed2a 100755
--- a/engine/src/flutter/tools/gn
+++ b/engine/src/flutter/tools/gn
@@ -120,6 +120,37 @@ def can_use_prebuilt_dart(args):
     prebuilts_dir = os.path.join(SRC_ROOT, 'flutter', 'prebuilts', prebuilt)
   return prebuilts_dir != None and os.path.isdir(prebuilts_dir)
 
+
+def get_target_cpu(args):
+  if args.target_os == 'android':
+    target_cpu = args.android_cpu
+  elif args.target_os == 'ios':
+    if args.simulator:
+      target_cpu = args.simulator_cpu
+    else:
+      target_cpu = args.ios_cpu
+  elif args.target_os == 'mac':
+    target_cpu = args.mac_cpu
+  elif args.target_os == 'linux':
+    target_cpu = args.linux_cpu
+  elif args.target_os == 'fuchsia':
+    target_cpu = args.fuchsia_cpu
+  elif args.target_os == 'wasm':
+    target_cpu = 'wasm'
+  elif args.target_os == 'win':
+    target_cpu = args.windows_cpu
+  else:
+    # Building host artifacts
+    target_cpu = 'x64'
+
+  # No cross-compilation on Windows (for now).
+  # See: https://github.com/flutter/engine/pull/3883
+  if sys.platform.startswith(('cygwin', 'win')) and args.target_os != 'win':
+    target_cpu = cpu_for_target_arch(target_cpu)
+
+  return target_cpu
+
+
 def to_gn_args(args):
     if args.simulator:
         if args.target_os != 'ios':
@@ -189,20 +220,14 @@ def to_gn_args(args):
       # The GN arg is not available in the windows toolchain.
       gn_args['enable_lto'] = enable_lto
 
-    if args.target_os == 'android':
-        gn_args['target_os'] = 'android'
-    elif args.target_os == 'ios':
-        gn_args['target_os'] = 'ios'
-        gn_args['use_ios_simulator'] = args.simulator
+    if args.target_os:
+      gn_args['target_os'] = args.target_os
+    gn_args['target_cpu'] = get_target_cpu(args)
+
+    if args.target_os == 'ios':
+      gn_args['use_ios_simulator'] = args.simulator
     elif args.target_os == 'mac':
-        gn_args['target_os'] = 'mac'
-        gn_args['use_ios_simulator'] = False
-    elif args.target_os == 'fuchsia':
-        gn_args['target_os'] = 'fuchsia'
-    elif args.target_os == 'wasm':
-        gn_args['target_os'] = 'wasm'
-    elif args.target_os is not None:
-        gn_args['target_os'] = args.target_os
+      gn_args['use_ios_simulator'] = False
 
     if args.dart_debug:
         gn_args['dart_debug'] = True
@@ -211,27 +236,6 @@ def to_gn_args(args):
       gn_args['dart_debug'] = True
       gn_args['dart_debug_optimization_level'] = '0'
 
-    if args.target_os == 'android':
-        gn_args['target_cpu'] = args.android_cpu
-    elif args.target_os == 'ios':
-        if args.simulator:
-            gn_args['target_cpu'] = args.simulator_cpu
-        else:
-            gn_args['target_cpu'] = args.ios_cpu
-    elif args.target_os == 'mac':
-      gn_args['target_cpu'] = args.mac_cpu
-    elif args.target_os == 'linux':
-      gn_args['target_cpu'] = args.linux_cpu
-    elif args.target_os == 'fuchsia':
-      gn_args['target_cpu'] = args.fuchsia_cpu
-    elif args.target_os == 'wasm':
-      gn_args['target_cpu'] = 'wasm'
-    elif args.target_os == 'win':
-      gn_args['target_cpu'] = args.windows_cpu
-    else:
-        # Building host artifacts
-        gn_args['target_cpu'] = 'x64'
-
     # Flutter-specific arguments which don't apply for a CanvasKit build.
     if args.target_os != 'wasm':
       gn_args['flutter_use_fontconfig'] = args.enable_fontconfig
@@ -270,10 +274,6 @@ def to_gn_args(args):
     if args.interpreter:
       raise Exception('--interpreter is no longer needed on any supported platform.')
 
-    if sys.platform.startswith(('cygwin', 'win')) and args.target_os != 'win':
-      if 'target_cpu' in gn_args:
-        gn_args['target_cpu'] = cpu_for_target_arch(gn_args['target_cpu'])
-
     if args.target_os is None:
       if sys.platform.startswith(('cygwin', 'win')):
         gn_args['dart_use_fallback_root_certificates'] = True