GN: Add ability to specify a depfile for custom targets.

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 375 matching lines @@
     "defines: C preprocessor defines.\n"
     "\n"
     "  A list of strings\n"
     "\n"
     "  These strings will be passed to the C/C++ compiler as #defines. The\n"
     "  strings may or may not include an \"=\" to assign a value.\n"
     "\n"
     "Example:\n"
     "  defines = [ \"AWESOME_FEATURE\", \"LOG_LEVEL=3\" ]\n";
 
+const char kDepfile[] = "depfile";
+const char kDepfile_HelpShort[] =
+    "depfile: [string] File name for input dependencies for custom targets.";
+const char kDepfile_Help[] =
+    "depfile: [string] File name for input dependencies for custom targets.\n"
+    "\n"
+    "  If nonempty, this string specifies that the current \"custom\" target\n"
+    "  will generate the given \".d\" file containing the dependencies of the\n"
+    "  input. Empty or unset means that the script doesn't generate the\n"
+    "  files.\n"
+    "\n"
+    "  The .d file should go in the target output directory. If you have more\n"
+    "  than one source file that the script is being run over, you can use\n"
+    "  the output file expansions described in \"gn help custom\" to name the\n"
+    "  .d file according to the input."
+    "\n"
+    "  The format is that of a Makefile, and all of the paths should be\n"
+    "  relative to the root build directory.\n"
+    "\n"
+    "Example:\n"
+    "  custom(\"myscript_target\") {\n"
+    "    script = \"myscript.py\"\n"
+    "    sources = [ ... ]\n"
+    "\n"
+    "    # Locate the depfile in the output directory named like the\n"
+    "    # inputs but with a \".d\" appended.\n"
+    "    depfile = \"$relative_target_output_dir/{{source_name}}.d\"\n"
+    "\n"
+    "    # Say our script uses \"-o <d file>\" to indicate the depfile.\n"
+    "    args = [ \"{{source}}\", \"-o\", depfile ]\n"
+    "  }\n";
+
 const char kDeps[] = "deps";
 const char kDeps_HelpShort[] =
     "deps: [label list] Linked dependencies.";
 const char kDeps_Help[] =
     "deps: Linked dependencies.\n"
     "\n"
     "  A list of target labels.\n"
     "\n"
     "  Specifies dependencies of a target. Shared and dynamic libraries will\n"
     "  be linked into the current target. Other target types that can't be\n"
@@ skipping 354 matching lines @@
     INSERT_VARIABLE(AllDependentConfigs)
     INSERT_VARIABLE(Args)
     INSERT_VARIABLE(Cflags)
     INSERT_VARIABLE(CflagsC)
     INSERT_VARIABLE(CflagsCC)
     INSERT_VARIABLE(CflagsObjC)
     INSERT_VARIABLE(CflagsObjCC)
     INSERT_VARIABLE(Configs)
     INSERT_VARIABLE(Data)
     INSERT_VARIABLE(Datadeps)
+    INSERT_VARIABLE(Depfile)
     INSERT_VARIABLE(Deps)
     INSERT_VARIABLE(DirectDependentConfigs)
     INSERT_VARIABLE(External)
     INSERT_VARIABLE(ForwardDependentConfigsFrom)
     INSERT_VARIABLE(GypFile)
     INSERT_VARIABLE(HardDep)
     INSERT_VARIABLE(IncludeDirs)
     INSERT_VARIABLE(Ldflags)
     INSERT_VARIABLE(Libs)
     INSERT_VARIABLE(LibDirs)
     INSERT_VARIABLE(OutputName)
     INSERT_VARIABLE(Outputs)
     INSERT_VARIABLE(Script)
     INSERT_VARIABLE(SourcePrereqs)
     INSERT_VARIABLE(Sources)
   }
   return info_map;
 }
 
 #undef INSERT_VARIABLE
 
 }  // namespace variables