Revert "Revert "find_headers.py to better find headers.""

This reverts commit 59da548b0c.

This now provides more information on failure and always sets the
source root for cases where the output directory is not a subdirectory
of the source directory.

Change-Id: I8e317814d4686d9a0736b7097b404920fa55e769
Reviewed-on: https://skia-review.googlesource.com/130134
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>

BUILD.gn

@@ -1013,7 +1013,9 @@ if (skia_enable_tools) {
     public_configs = [ ":skia.h_config" ]
     skia_h = "$target_gen_dir/skia.h"
     script = "gn/find_headers.py"
-    args = [ rebase_path(skia_h, root_build_dir) ] +
+    args = [ rebase_path("//bin/gn") ] +
+           [ rebase_path("//") ] +
+           [ rebase_path(skia_h, root_build_dir) ] +
            rebase_path(skia_public_includes)
     depfile = "$skia_h.deps"
     outputs = [

gn/core.gni

@@ -392,6 +392,7 @@ skia_core_sources = [
   "$_include/core/SkData.h",
   "$_include/core/SkDeferredDisplayListRecorder.h",
   "$_include/core/SkDeque.h",
+  "$_include/core/SkDocument.h",
   "$_include/core/SkDrawable.h",
   "$_include/core/SkDrawFilter.h",
   "$_include/core/SkDrawLooper.h",

gn/find_headers.py

@@ -5,43 +5,83 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import collections
+import json
 import os
+import subprocess
 import sys
 
-# We'll recursively search each include directory for headers,
-# then write them to skia.h with a small blacklist.
+# Finds all public sources in include directories then write them to skia.h.
 
-# We'll also write skia.h.deps, which Ninja uses to track dependencies. It's the
+# Also write skia.h.deps, which Ninja uses to track dependencies. It's the
 # very same mechanism Ninja uses to know which .h files affect which .cpp files.
 
-skia_h       = sys.argv[1]
-include_dirs = sys.argv[2:]
+gn              = sys.argv[1]
+absolute_source = sys.argv[2]
+skia_h          = sys.argv[3]
+include_dirs    = sys.argv[4:]
 
-blacklist = {
-  "GrGLConfig_chrome.h",
-  "SkFontMgr_fontconfig.h",
-}
+absolute_source = os.path.normpath(absolute_source)
 
-headers = []
-for directory in include_dirs:
-  for f in os.listdir(directory):
-    if os.path.isfile(os.path.join(directory, f)):
-      if f.endswith('.h') and f not in blacklist:
-        headers.append(os.path.join(directory,f))
-headers.sort()
+include_dirs = [os.path.join(os.path.normpath(include_dir), '')
+                for include_dir in include_dirs]
+include_dirs.sort(key=len, reverse=True)
 
-with open(skia_h, "w") as f:
+# If skia ever uses 'public' that will need to be considered as well or instead.
+gn_sources_cmd = [gn, 'desc', '.', '--root=%s' % absolute_source,
+                  '--format=json', '*', 'sources']
+
+sources_json_txt = ''
+try:
+  sources_json_txt = subprocess.check_output(gn_sources_cmd)
+except subprocess.CalledProcessError as e:
+  print e.output
+  raise
+
+sources_json = {}
+try:
+  sources_json = json.loads(sources_json_txt)
+except ValueError:
+  print sources_json_txt
+  raise
+
+sources = {os.path.join(absolute_source, os.path.normpath(source[2:]))
+           for target in sources_json.itervalues()
+           for source in target.get('sources', [])}
+
+Header = collections.namedtuple('Header', ['absolute', 'include'])
+headers = {}
+for source in sources:
+  source_as_include = [source[len(include_dir):]
+                       for include_dir in include_dirs
+                       if source.startswith(include_dir)]
+  if not source_as_include:
+    continue
+  statinfo = os.stat(source)
+  key = str(statinfo.st_ino) + ':' + str(statinfo.st_dev)
+  # On Windows os.stat st_ino is 0 until 3.3.4 and st_dev is 0 until 3.4.0.
+  if key == '0:0':
+    key = source
+  include_path = source_as_include[0]
+  if key not in headers or len(include_path) < len(headers[key].include):
+    headers[key] = Header(source, include_path)
+
+headers = headers.values()
+headers.sort(key=lambda x: x.include)
+
+with open(skia_h, 'w') as f:
   f.write('// skia.h generated by GN.\n')
   f.write('#ifndef skia_h_DEFINED\n')
   f.write('#define skia_h_DEFINED\n')
-  for h in headers:
-    f.write('#include "' + os.path.basename(h) + '"\n')
+  for header in headers:
+    f.write('#include "' + header.include + '"\n')
   f.write('#endif//skia_h_DEFINED\n')
 
-with open(skia_h + '.deps', "w") as f:
+with open(skia_h + '.deps', 'w') as f:
   f.write(skia_h + ':')
-  for h in headers:
-    f.write(' ' + h)
+  for header in headers:
+    f.write(' ' + header.absolute)
+  f.write(' build.ninja.d')
   f.write('\n')
 
 # Temporary: during development this file wrote skia.h.d, not skia.h.deps,