Add optional public header checking to GN build

tools/gn/variables.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/variables.h"
 
 namespace variables {
 
 // Built-in variables ----------------------------------------------------------
 
@@ skipping 660 matching lines @@
     "\n"
     "  Outputs is valid for \"copy\", \"action\", and \"action_foreach\"\n"
     "  target types and indicates the resulting files. The values may contain\n"
     "  source expansions to generate the output names from the sources (see\n"
     "  \"gn help source_expansion\").\n"
     "\n"
     "  For copy targets, the outputs is the destination for the copied\n"
     "  file(s). For actions, the outputs should be the list of files\n"
     "  generated by the script.\n";
 
+const char kPublic[] = "public";
+const char kPublic_HelpShort[] =
+    "public: [file list] Declare public header files for a target.";
+const char kPublic_Help[] =
+    "public: Declare public header files for a target.\n"
+    "\n"
+    "  A list of files and patterns that other targets can include. These\n"
+    "  permissions are checked via the \"check\" command\n"
+    "  (see \"gn help check\").\n"
+    "\n"
+    "  If no public files are declared, other targets (assuming they have\n"
+    "  visibility to depend on this target) can include any file. If this\n"
+    "  variable is defined on a target, dependent targets may only include\n"
+    "  files on this whitelist.\n"
+    "\n"
+    "  The entries in this list are patterns (see \"gn help patterns\") so\n"
+    "  you can use simple wildcard matching if you have a directory of public\n"
+    "  files.\n"
+    "\n"
+    "  Header file permissions are also subject to visibility. A target\n"
+    "  must be visible to another target to include any files from it at all\n"
+    "  and the public headers indicate which subset of those files are\n"
+    "  permitted.\n"
+    "\n"
+    "  Public files are inherited through the dependency tree. So if there is\n"
+    "  a dependency A -> B -> C, then A can include C's public headers.\n"
+    "  However, the same is NOT true of visibility, so unless A is in C's\n"
+    "  visibility list, the include will be rejected.\n"
+    "\n"
+    "Examples:\n"
+    "  These exact files are public:\n"
+    "    public = [ \"foo.h\", \"bar.h\" ]\n"
+    "\n"
+    "  All files in the \"public\" directory are public:\n"
+    "    public = [ \"public/*\" ]\n"
+    "\n"
+    "  No files are public (no targets may include headers from this one):\n"
+    "    public = []\n";
+
 const char kScript[] = "script";
 const char kScript_HelpShort[] =
     "script: [file name] Script file for actions.";
 const char kScript_Help[] =
     "script: Script file for actions.\n"
     "\n"
     "  An absolute or buildfile-relative file name of a Python script to run\n"
     "  for a action and action_foreach targets (see \"gn help action\" and\n"
     "  \"gn help action_foreach\").\n";
 
@@ skipping 172 matching lines @@
     INSERT_VARIABLE(DirectDependentConfigs)
     INSERT_VARIABLE(ForwardDependentConfigsFrom)
     INSERT_VARIABLE(HardDep)
     INSERT_VARIABLE(IncludeDirs)
     INSERT_VARIABLE(Ldflags)
     INSERT_VARIABLE(Libs)
     INSERT_VARIABLE(LibDirs)
     INSERT_VARIABLE(OutputExtension)
     INSERT_VARIABLE(OutputName)
     INSERT_VARIABLE(Outputs)
+    INSERT_VARIABLE(Public)
     INSERT_VARIABLE(Script)
     INSERT_VARIABLE(SourcePrereqs)
     INSERT_VARIABLE(Sources)
     INSERT_VARIABLE(Visibility)
   }
   return info_map;
 }
 
 #undef INSERT_VARIABLE
 
 }  // namespace variables