tools/generate_compile_commands.py conform to style guide

Change-Id: I7d0b917968cf232fde4d0650e25d82fa6b4caefe
Reviewed-on: https://dart-review.googlesource.com/c/86881
Reviewed-by: Zach Anderson <zra@google.com>

tools/generate_compile_commands.py

@@ -4,45 +4,75 @@
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-import subprocess
+import argparse
+import generate_buildfiles
 import json
+import subprocess
+import sys
 import utils
+import os
 
-### Python script to generate compile_commands.json and make it more useful.
+# Python script to generate compile_commands.json which is used by the clang
+# and intellij language analysis servers used in IDEs such as Visual Studio
+# Code and Emacs.
 
 HOST_OS = utils.GuessOS()
 
-if not HOST_OS in ['linux', 'macos']:
-  print ("Generate compile_commands has not been ported to %s yet." % (HOST_OS))
-  exit
 
-if HOST_OS == 'linux':
-  ninja = 'ninja-linux64'
-  out_folder = ' out'
-if HOST_OS == 'macos':
-  ninja = 'ninja-mac'
-  out_folder = ' xcodebuild'
+def GenerateCompileCommands(options):
+  gn_result = generate_buildfiles.RunGn(options)
+  if (gn_result != 0):
+    return gn_result
 
-subprocess.call("python tools/generate_buildfiles.py", shell=True)
+  out_folder = utils.GetBuildRoot(HOST_OS, mode="debug", arch="x64")
 
-command_set = json.loads(
-  subprocess.check_output(
-    ninja + " -C " + out_folder + "/DebugX64 -t compdb cxx cc h", shell=True
+  if (not os.path.isdir(out_folder)):
+    return 1
+
+  command_set = json.loads(
+      subprocess.check_output(
+          ["ninja", "-C", out_folder, "-t", "compdb", "cxx", "cc", "h"]
+      )
   )
-)
 
-commands = []
-for obj in command_set:
-  C = obj["command"]
+  commands = []
+  for obj in command_set:
+    command = obj["command"]
 
-  # Skip precompiled mode, a lot of code is commented out in precompiled mode
-  if ("-DDART_PRECOMPILED_RUNTIME" in C):
-    continue
+    # Skip precompiled mode, a lot of code is commented out in precompiled mode
+    if ("-DDART_PRECOMPILED_RUNTIME" in command):
+      continue
 
-  # Remove warnings
-  C = C.replace("-Werror", "")
+    # Remove warnings
+    command = command.replace("-Werror", "")
 
-  obj["command"] = C
-  commands += [obj]
+    obj["command"] = command
+    commands += [obj]
 
-json.dump(commands, open("compile_commands.json", "w"), indent=4)
+  json.dump(commands, open("compile_commands.json", "w"), indent=4)
+
+  return 0
+
+
+def ParseArgs(args):
+  args = args[1:]
+  parser = argparse.ArgumentParser(
+      description="A script to generate compile_commands.json which is used by"
+      + "the clang and intellij language analysis servers used in IDEs such as"
+      + "Visual Studio Code and Emacs")
+
+  parser.add_argument("-v", "--verbose",
+                      help='Verbose output.',
+                      default=False,
+                      action="store_true")
+
+  return parser.parse_args(args)
+
+
+def main(argv):
+  options = ParseArgs(argv)
+  return GenerateCompileCommands(options)
+
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv))