Add initial prototype for the GN meta-buildsystem.

tools/gn/functions_target.cc

Index: tools/gn/functions_target.cc
diff --git a/tools/gn/functions_target.cc b/tools/gn/functions_target.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a5991e777ca9d903ab718d46763d2e8c66908ad7
--- /dev/null
+++ b/tools/gn/functions_target.cc
@@ -0,0 +1,221 @@
+// 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/err.h"
+#include "tools/gn/parse_tree.h"
+#include "tools/gn/scope.h"
+#include "tools/gn/target_generator.h"
+#include "tools/gn/value.h"
+
+namespace {
+
+Value ExecuteGenericTarget(const char* target_type,
+                           Scope* scope,
+                           const FunctionCallNode* function,
+                           const std::vector<Value>& args,
+                           BlockNode* block,
+                           Err* err) {
+  if (!EnsureNotProcessingImport(function, scope, err) ||
+      !EnsureNotProcessingBuildConfig(function, scope, err))
+    return Value();
+  Scope block_scope(scope);
+  if (!FillTargetBlockScope(scope, function, target_type, block,
+                            args, &block_scope, err))
+    return Value();
+
+  block->ExecuteBlockInScope(&block_scope, err);
+  if (err->has_error())
+    return Value();
+
+  TargetGenerator::GenerateTarget(&block_scope, function->function(), args,
+                                  target_type, err);
+
+  block_scope.CheckForUnusedVars(err);
+  return Value();
+}
+
+}  // namespace
+
+Value ExecuteComponent(Scope* scope,
+                       const FunctionCallNode* function,
+                       const std::vector<Value>& args,
+                       BlockNode* block,
+                       Err* err) {
+  // A component is either a shared or static library, depending on the value
+  // of |component_mode|.
+  const Value* component_mode_value = scope->GetValue("component_mode");
+
+  static const char helptext[] =
+      "You're declaring a component here but have not defined "
+      "\"component_mode\" to\neither \"shared_library\" or \"static_library\".";
+  if (!component_mode_value) {
+    *err = Err(function->function(), "No component mode set.", helptext);
+    return Value();
+  }
+  if (component_mode_value->type() != Value::STRING ||
+      (component_mode_value->string_value() != functions::kSharedLibrary &&
+       component_mode_value->string_value() != functions::kStaticLibrary)) {
+    *err = Err(function->function(), "Invalid component mode set.", helptext);
+    return Value();
+  }
+  const std::string& component_mode = component_mode_value->string_value();
+
+  if (!EnsureNotProcessingImport(function, scope, err))
+    return Value();
+  Scope block_scope(scope);
+  if (!FillTargetBlockScope(scope, function, component_mode.c_str(), block,
+                            args, &block_scope, err))
+    return Value();
+
+  block->ExecuteBlockInScope(&block_scope, err);
+  if (err->has_error())
+    return Value();
+
+  TargetGenerator::GenerateTarget(&block_scope, function->function(), args,
+                                  component_mode, err);
+  return Value();
+}
+
+Value ExecuteCopy(Scope* scope,
+                  const FunctionCallNode* function,
+                  const std::vector<Value>& args,
+                  Err* err) {
+  if (!EnsureNotProcessingImport(function, scope, err) ||
+      !EnsureNotProcessingBuildConfig(function, scope, err))
+    return Value();
+  TargetGenerator::GenerateTarget(scope, function->function(), args,
+                                  functions::kCopy, err);
+  return Value();
+}
+
+/*
+custom: Declare a script-generated target.
+
+  This target type allows you to run a script over a set of sources files and
+  generate a set of output files.
+
+  The script will be executed with the given arguments with the current
+  directory being that of the current BUILD file.
+
+  There are two modes. The first mode is the "per-file" mode where you
+  specify a list of sources and the script is run once for each one as a build
+  rule. In this case, each file specified in the |outputs| variable must be
+  unique when applied to each source file (normally you would reference
+  "{{source_name_part}}" from within each one) or the build system will get
+  confused about how to build those files. You should use the |data| variable
+  to list all additional dependencies of your script: these will be added
+  as dependencies for each build step.
+
+  The second mode is when you just want to run a script once rather than as a
+  general rule over a set of files. In this case you don't list any sources.
+  Dependencies of your script are specified only in the |data| variable and
+  your |outputs| variable should just list all outputs.
+
+Variables:
+
+  args, data, deps, outputs, script*, sources
+  * = required
+
+  There are some special substrings that will be searched for when processing
+  some variables:
+
+    "{{source}}"
+        Expanded in |args|, this is the name of the source file relative to the
+        current directory when running the script. This is how you specify
+        the current input file to your script.
+
+    "{{source_name_part}}"
+        Expanded in |args| and |outputs|, this is just the filename part of the
+        current source file with no directory or extension. This is how you
+        specify a name transoformation to the output. Normally you would
+        write an output as "$target_output_dir/{{source_name_part}}.o".
+
+  All |outputs| files must be inside the output directory of the build. You
+  would generally use "$target_output_dir" or "$target_gen_dir" to reference
+  the output or generated intermediate file directories, respectively.
+
+Examples:
+
+  custom("general_rule") {
+    script = "do_processing.py"
+    sources = [ "foo.idl" ]
+    data = [ "my_configuration.txt" ]
+    outputs = [ "$target_gen_dir/{{source_name_part}}.h" ]
+    args = [ "{{source}}",
+             "-o", "$relative_target_gen_dir/{{source_name_part}}.h" ]
+  }
+
+  custom("just_run_this_guy_once") {
+    script = "doprocessing.py"
+    data = [ "my_configuration.txt" ]
+    outputs = [ "$target_gen_dir/insightful_output.txt" ]
+    args = [ "--output_dir", $target_gen_dir ]
+  }
+*/
+Value ExecuteCustom(Scope* scope,
+                    const FunctionCallNode* function,
+                    const std::vector<Value>& args,
+                    BlockNode* block,
+                    Err* err) {
+  return ExecuteGenericTarget(functions::kCustom, scope, function, args,
+                              block, err);
+}
+
+Value ExecuteExecutable(Scope* scope,
+                        const FunctionCallNode* function,
+                        const std::vector<Value>& args,
+                        BlockNode* block,
+                        Err* err) {
+  return ExecuteGenericTarget(functions::kExecutable, scope, function, args,
+                              block, err);
+}
+
+Value ExecuteSharedLibrary(Scope* scope,
+                           const FunctionCallNode* function,
+                           const std::vector<Value>& args,
+                           BlockNode* block,
+                           Err* err) {
+  return ExecuteGenericTarget(functions::kSharedLibrary, scope, function, args,
+                              block, err);
+}
+
+Value ExecuteStaticLibrary(Scope* scope,
+                           const FunctionCallNode* function,
+                           const std::vector<Value>& args,
+                           BlockNode* block,
+                           Err* err) {
+  return ExecuteGenericTarget(functions::kStaticLibrary, scope, function, args,
+                              block, err);
+}
+
+/*
+group: Declare a group of targets.
+
+  This target type allows you to create meta-targets that just collect a set
+  of dependencies into one named target.
+
+Variables:
+
+  deps
+
+Example:
+
+  group("all") {
+    deps = [
+      "//project:runner",
+      "//project:unit_tests",
+    ]
+  }
+*/
+Value ExecuteGroup(Scope* scope,
+                   const FunctionCallNode* function,
+                   const std::vector<Value>& args,
+                   BlockNode* block,
+                   Err* err) {
+  return ExecuteGenericTarget(functions::kGroup, scope, function, args,
+                              block, err);
+}
+