gyp: add compile_commands.json gyp generator

this is a re-base of the gyp part of
3c46bb9
after bumping GYP version to
https://chromium.googlesource.com/external/gyp/+/eb296f67da078ec01f5e3a9ea9cdc6d26d680161

Original-Review-By: James M Snell <jasnell@gmail.com>
Ref: nodejs/node#7986
PR-URL: nodejs/node#12450
Reviewed-By: João Reis <reis@janeasystems.com>

tools/gyp/pylib/gyp/generator/compile_commands_json.py

@@ -0,0 +1,115 @@
+# Copyright (c) 2016 Ben Noordhuis <info@bnoordhuis.nl>. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import gyp.common
+import gyp.xcode_emulation
+import json
+import os
+
+generator_additional_non_configuration_keys = []
+generator_additional_path_sections = []
+generator_extra_sources_for_rules = []
+generator_filelist_paths = None
+generator_supports_multiple_toolsets = True
+generator_wants_sorted_dependencies = False
+
+# Lifted from make.py.  The actual values don't matter much.
+generator_default_variables = {
+  'CONFIGURATION_NAME': '$(BUILDTYPE)',
+  'EXECUTABLE_PREFIX': '',
+  'EXECUTABLE_SUFFIX': '',
+  'INTERMEDIATE_DIR': '$(obj).$(TOOLSET)/$(TARGET)/geni',
+  'PRODUCT_DIR': '$(builddir)',
+  'RULE_INPUT_DIRNAME': '%(INPUT_DIRNAME)s',
+  'RULE_INPUT_EXT': '$(suffix $<)',
+  'RULE_INPUT_NAME': '$(notdir $<)',
+  'RULE_INPUT_PATH': '$(abspath $<)',
+  'RULE_INPUT_ROOT': '%(INPUT_ROOT)s',
+  'SHARED_INTERMEDIATE_DIR': '$(obj)/gen',
+  'SHARED_LIB_PREFIX': 'lib',
+  'STATIC_LIB_PREFIX': 'lib',
+  'STATIC_LIB_SUFFIX': '.a',
+}
+
+
+def IsMac(params):
+  return 'mac' == gyp.common.GetFlavor(params)
+
+
+def CalculateVariables(default_variables, params):
+  default_variables.setdefault('OS', gyp.common.GetFlavor(params))
+
+
+def AddCommandsForTarget(cwd, target, params, per_config_commands):
+  output_dir = params['generator_flags']['output_dir']
+  for configuration_name, configuration in target['configurations'].iteritems():
+    builddir_name = os.path.join(output_dir, configuration_name)
+
+    if IsMac(params):
+      xcode_settings = gyp.xcode_emulation.XcodeSettings(target)
+      cflags = xcode_settings.GetCflags(configuration_name)
+      cflags_c = xcode_settings.GetCflagsC(configuration_name)
+      cflags_cc = xcode_settings.GetCflagsCC(configuration_name)
+    else:
+      cflags = configuration.get('cflags', [])
+      cflags_c = configuration.get('cflags_c', [])
+      cflags_cc = configuration.get('cflags_cc', [])
+
+    cflags_c = cflags + cflags_c
+    cflags_cc = cflags + cflags_cc
+
+    defines = configuration.get('defines', [])
+    defines = ['-D' + s for s in defines]
+
+    # TODO(bnoordhuis) Handle generated source files.
+    sources = target.get('sources', [])
+    sources = [s for s in sources if s.endswith('.c') or s.endswith('.cc')]
+
+    def resolve(filename):
+      return os.path.abspath(os.path.join(cwd, filename))
+
+    # TODO(bnoordhuis) Handle generated header files.
+    include_dirs = configuration.get('include_dirs', [])
+    include_dirs = [s for s in include_dirs if not s.startswith('$(obj)')]
+    includes = ['-I' + resolve(s) for s in include_dirs]
+
+    defines = gyp.common.EncodePOSIXShellList(defines)
+    includes = gyp.common.EncodePOSIXShellList(includes)
+    cflags_c = gyp.common.EncodePOSIXShellList(cflags_c)
+    cflags_cc = gyp.common.EncodePOSIXShellList(cflags_cc)
+
+    commands = per_config_commands.setdefault(configuration_name, [])
+    for source in sources:
+      file = resolve(source)
+      isc = source.endswith('.c')
+      cc = 'cc' if isc else 'c++'
+      cflags = cflags_c if isc else cflags_cc
+      command = ' '.join((cc, defines, includes, cflags,
+                          '-c', gyp.common.EncodePOSIXShellArgument(file)))
+      commands.append(dict(command=command, directory=output_dir, file=file))
+
+
+def GenerateOutput(target_list, target_dicts, data, params):
+  per_config_commands = {}
+  for qualified_target, target in target_dicts.iteritems():
+    build_file, target_name, toolset = (
+        gyp.common.ParseQualifiedTarget(qualified_target))
+    if IsMac(params):
+      settings = data[build_file]
+      gyp.xcode_emulation.MergeGlobalXcodeSettingsToSpec(settings, target)
+    cwd = os.path.dirname(build_file)
+    AddCommandsForTarget(cwd, target, params, per_config_commands)
+
+  output_dir = params['generator_flags']['output_dir']
+  for configuration_name, commands in per_config_commands.iteritems():
+    filename = os.path.join(output_dir,
+                            configuration_name,
+                            'compile_commands.json')
+    gyp.common.EnsureDirExists(filename)
+    fp = open(filename, 'w')
+    json.dump(commands, fp=fp, indent=0, check_circular=False)
+
+
+def PerformBuild(data, configurations, params):
+  pass