Add GN function get_label_info

tools/gn/function_get_label_info.cc

Index: tools/gn/function_get_label_info.cc
diff --git a/tools/gn/function_get_label_info.cc b/tools/gn/function_get_label_info.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c097941e278ca3c9849d8d826629ce6f8d1a4605
--- /dev/null
+++ b/tools/gn/function_get_label_info.cc
@@ -0,0 +1,153 @@
+// Copyright 2014 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/err.h"
+#include "tools/gn/filesystem_utils.h"
+#include "tools/gn/functions.h"
+#include "tools/gn/label.h"
+#include "tools/gn/parse_tree.h"
+#include "tools/gn/value.h"
+
+namespace functions {
+
+const char kGetLabelInfo[] = "get_label_info";
+const char kGetLabelInfo_HelpShort[] =
+    "get_label_info: Get an attribute from a target's label.";
+const char kGetLabelInfo_Help[] =
+    "get_label_info: Get an attribute from a target's label.\n"
+    "\n"
+    "  get_label_info(target_label, what)\n"
+    "\n"
+    "  Given the label of a target, returns some attribute of that target.\n"
+    "  The target need not have been previously defined in the same file,\n"
+    "  since none of the attributes depend on the actual target definition,\n"
+    "  only the label itself.\n"
+    "\n"
+    "  See also \"gn help get_target_outputs\".\n"
+    "\n"
+    "Possible values for the \"what\" parameter\n"
+    "\n"
+    "  \"name\"\n"
+    "      The short name of the target. This will match the value of the\n"
+    "      \"target_name\" variable inside that target's declaration. For the\n"
+    "      label \"//foo/bar:baz\" this will return \"baz\".\n"
+    "\n"
+    "  \"dir\"\n"
+    "      The directory containing the target's definition, with no slash at\n"
+    "      the end. For the label \"//foo/bar:baz\" this will return\n"
+    "      \"//foo/bar\".\n"
+    "\n"
+    "  \"target_gen_dir\"\n"
+    "      The generated file directory for the target. This will match the\n"
+    "      value of the \"target_gen_dir\" variable when inside that target's\n"
+    "      declaration.\n"
+    "\n"
+    "  \"root_gen_dir\"\n"
+    "      The root of the generated file tree for the target. This will\n"
+    "      match the value of the \"root_gen_dir\" variable when inside that\n"
+    "      target's declaration.\n"
+    "\n"
+    "  \"target_out_dir\n"
+    "      The output directory for the target. This will match the\n"
+    "      value of the \"target_out_dir\" variable when inside that target's\n"
+    "      declaration.\n"
+    "\n"
+    "  \"root_out_dir\"\n"
+    "      The root of the output file tree for the target. This will\n"
+    "      match the value of the \"root_gen_dir\" variable when inside that\n"
+    "      target's declaration.\n"
+    "\n"
+    "  \"label_no_toolchain\"\n"
+    "      The fully qualified version of this label, not including the\n"
+    "      toolchain. For the input \":bar\" it might return\n"
+    "      \"//foo:bar\".\n"
+    "\n"
+    "  \"label_with_toolchain\"\n"
+    "      The fully qualified version of this label, including the\n"
+    "      toolchain. For the input \":bar\" it might return\n"
+    "      \"//foo:bar(//toolchain:x64)\".\n"
+    "\n"
+    "  \"toolchain\"\n"
+    "      The label of the toolchain. This will match the value of the\n"
+    "      \"current_toolchain\" variable when inside that target's\n"
+    "      declaration.\n"
+    "\n"
+    "Examples\n"
+    "\n"
+    "  get_label_info(\":foo\", \"name\")\n"
+    "  # Returns string \"foo\".\n"
+    "\n"
+    "  get_label_info(\"//foo/bar:baz\", \"gen_dir\")\n"
+    "  # Returns string \"//out/Debug/gen/foo/bar\".\n";
+
+Value RunGetLabelInfo(Scope* scope,
+                      const FunctionCallNode* function,
+                      const std::vector<Value>& args,
+                      Err* err) {
+  if (args.size() != 2) {
+    *err = Err(function, "Expected two arguments.");
+    return Value();
+  }
+
+  // Resolve the requested label.
+  Label label = Label::Resolve(scope->GetSourceDir(),
+                               ToolchainLabelForScope(scope), args[0], err);
+  if (label.is_null())
+    return Value();
+
+  // Extract the "what" parameter.
+  if (!args[1].VerifyTypeIs(Value::STRING, err))
+    return Value();
+  const std::string& what = args[1].string_value();
+
+  Value result(function, Value::STRING);
+  if (what == "name") {
+    result.string_value() = label.name();
+
+  } else if (what == "dir") {
+    result.string_value() = DirectoryWithNoLastSlash(label.dir());
+
+  } else if (what == "target_gen_dir") {
+    result.string_value() = DirectoryWithNoLastSlash(
+        GetGenDirForSourceDir(scope->settings(), label.dir()));
+
+  } else if (what == "root_gen_dir") {
+    Label toolchain_label = label.GetToolchainLabel();
+    bool is_default =
+        scope->settings()->default_toolchain_label() == toolchain_label;
+    result.string_value() = DirectoryWithNoLastSlash(
+        GetToolchainGenDir(scope->settings()->build_settings(),
+                           toolchain_label, is_default));
+
+  } else if (what == "target_out_dir") {
+    result.string_value() = DirectoryWithNoLastSlash(
+        GetOutputDirForSourceDir(scope->settings(), label.dir()));
+
+  } else if (what == "root_out_dir") {
+    Label toolchain_label = label.GetToolchainLabel();
+    bool is_default =
+        scope->settings()->default_toolchain_label() == toolchain_label;
+    result.string_value() = DirectoryWithNoLastSlash(
+        GetToolchainOutputDir(scope->settings()->build_settings(),
+                              toolchain_label, is_default));
+
+  } else if (what == "toolchain") {
+    result.string_value() = label.GetToolchainLabel().GetUserVisibleName(false);
+
+  } else if (what == "label_no_toolchain") {
+    result.string_value() =
+        label.GetWithNoToolchain().GetUserVisibleName(false);
+
+  } else if (what == "label_with_toolchain") {
+    result.string_value() = label.GetUserVisibleName(true);
+
+  } else {
+    *err = Err(args[1], "Unknown value for \"what\" parameter.");
+    return Value();
+  }
+
+  return result;
+}
+
+}  // namespace functions