Support deps for actions in GN.

tools/gn/functions_target.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/functions.h"
 
 #include "tools/gn/config_values_generator.h"
 #include "tools/gn/err.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/scope.h"
@@ skipping 52 matching lines @@
     "  sources, outputs, and source_prereqs will be all treated as relative\n" \
     "  to the current build file and converted as needed automatically).\n"
 
 // Common help paragraph on script output directories.
 #define SCRIPT_EXECUTION_OUTPUTS \
     "  All output files must be inside the output directory of the build.\n" \
     "  You would generally use |$target_out_dir| or |$target_gen_dir| to\n" \
     "  reference the output or generated intermediate file directories,\n" \
     "  respectively.\n"
 
+#define ACTION_DEPS \
+    "  The \"deps\" for an action will always be completed before any part\n" \
+    "  of the action is run so it can depend on the output of previous\n" \
+    "  steps. The \"datadeps\" will be built if the action is built, but\n" \
+    "  may not have completed before all steps of the action are started.\n" \
+    "  This can give additional parallelism in the build for runtime-only\n" \
+    "  dependencies.\n"
+
 const char kAction[] = "action";
 const char kAction_HelpShort[] =
     "action: Declare a target that runs a script a single time.";
 const char kAction_Help[] =
     "action: Declare a target that runs a script a single time.\n"
     "\n"
     "  This target type allows you to run a script a single time to produce\n"
     "  or more output files. If you want to run a script once for each of a\n"
     "  set of input files, see \"gn help action_foreach\".\n"
     "\n"
+    "Inputs\n"
+    "\n"
     "  In an action the \"sources\" and \"source_prereqs\" are treated the\n"
     "  same: they're both input dependencies on script execution with no\n"
     "  special handling. If you want to pass the sources to your script, you\n"
     "  must do so explicitly by including them in the \"args\". Note also\n"
     "  that this means there is no special handling of paths since GN\n"
     "  doesn't know which of the args are paths and not. You will want to use\n"
     "  rebase_path() to convert paths to be relative to the root_build_dir.\n"
     "\n"
     "  It is recommended you put inputs to your script in the \"sources\"\n"
     "  variable, and stuff like other Python files required to run your\n"
     "  script in the \"source_prereqs\" variable.\n"
     "\n"
+    ACTION_DEPS
+    "\n"
+    "Outputs\n"
+    "\n"
     "  You should specify files created by your script by specifying them in\n"
     "  the \"outputs\".\n"
     "\n"
     SCRIPT_EXECUTION_CONTEXT
     "\n"
     "File name handling\n"
     "\n"
     SCRIPT_EXECUTION_OUTPUTS
     "\n"
     "Variables\n"
@@ skipping 33 matching lines @@
 const char kActionForEach[] = "action_foreach";
 const char kActionForEach_HelpShort[] =
     "action_foreach: Declare a target that runs a script over a set of files.";
 const char kActionForEach_Help[] =
     "action_foreach: Declare a target that runs a script over a set of files.\n"
     "\n"
     "  This target type allows you to run a script once-per-file over a set\n"
     "  of sources. If you want to run a script once that takes many files as\n"
     "  input, see \"gn help action\".\n"
     "\n"
+    "Inputs\n"
+    "\n"
     "  The script will be run once per file in the \"sources\" variable. The\n"
     "  \"outputs\" variable should specify one or more files with a source\n"
     "  expansion pattern in it (see \"gn help source_expansion\"). The output\n"
     "  file(s) for each script invocation should be unique. Normally you\n"
     "  use \"{{source_name_part}}\" in each output file.\n"
     "\n"
     "  If your script takes additional data as input, such as a shared\n"
     "  configuration file or a Python module it uses, those files should be\n"
     "  listed in the \"source_prereqs\" variable. These files are treated as\n"
     "  dependencies of each script invocation.\n"
     "\n"
+    ACTION_DEPS
+    "\n"
+    "Outputs\n"
+    "\n"
     SCRIPT_EXECUTION_CONTEXT
     "\n"
     "File name handling\n"
     "\n"
     SCRIPT_EXECUTION_OUTPUTS
     "\n"
     "Variables\n"
     "\n"
     "  args, data, datadeps, depfile, deps, outputs*, script*,\n"
     "  source_prereqs, sources*\n"
@@ skipping 341 matching lines @@
 Value RunTest(Scope* scope,
               const FunctionCallNode* function,
               const std::vector<Value>& args,
               BlockNode* block,
               Err* err) {
   return ExecuteGenericTarget(functions::kExecutable, scope, function, args,
                               block, err);
 }
 
 }  // namespace functions