Enhance GN diagnostic tools

tools/gn/command_check.cc

Index: tools/gn/command_check.cc
diff --git a/tools/gn/command_check.cc b/tools/gn/command_check.cc
index 3546b7c1aa945580d307bd15a57c0986f9be006b..74ffb42e098a24f4062fc142bfb725d99dc22da9 100644
--- a/tools/gn/command_check.cc
+++ b/tools/gn/command_check.cc
@@ -3,8 +3,10 @@
 // found in the LICENSE file.
 
 #include "tools/gn/commands.h"
+#include "tools/gn/header_checker.h"
 #include "tools/gn/setup.h"
 #include "tools/gn/standard_out.h"
+#include "tools/gn/trace.h"
 
 namespace commands {
 
@@ -12,28 +14,81 @@ const char kCheck[] = "check";
 const char kCheck_HelpShort[] =
     "check: Check header dependencies.";
 const char kCheck_Help[] =
-    "gn check: Check header dependencies.\n"
+    "gn check <out_dir> [<target label>]\n"
     "\n"
     "  \"gn check\" is the same thing as \"gn gen\" with the \"--check\" flag\n"
     "  except that this command does not write out any build files. It's\n"
     "  intended to be an easy way to manually trigger include file checking.\n"
     "\n"
-    "  See \"gn help\" for the common command-line switches.\n";
+    "  The <label_pattern> can take exact labels or patterns that match more\n"
+    "  than one (although not general regular expressions). If specified,\n"
+    "  only those matching targets will be checked.\n"
+    "  See \"gn help label_pattern\" for details.\n"
+    "\n"
+    "  See \"gn help\" for the common command-line switches.\n"
+    "\n"
+    "Examples\n"
+    "\n"
+    "  gn check out/Debug\n"
+    "      Check everything.\n"
+    "\n"
+    "  gn check out/Default //foo:bar\n"
+    "      Check only the files in the //foo:bar target.\n"
+    "\n"
+    "  gn check out/Default \"//foo/*\n"
+    "      Check only the files in targets in the //foo directory tree.\n";
 
 int RunCheck(const std::vector<std::string>& args) {
+  if (args.size() != 1 && args.size() != 2) {
+    Err(Location(), "You're holding it wrong.",
+        "Usage: \"gn check <out_dir> [<target_label>]\"").PrintToStdout();
+    return 1;
+  }
+
   // Deliberately leaked to avoid expensive process teardown.
   Setup* setup = new Setup();
-  // TODO(brettw) bug 343726: Use a temporary directory instead of this
-  // default one to avoid messing up any build that's in there.
-  if (!setup->DoSetup("//out/Default"))
+  if (!setup->DoSetup(args[0]))
     return 1;
-  setup->set_check_public_headers(true);
-
   if (!setup->Run())
     return 1;
 
+  std::vector<const Target*> targets_to_check;
+  if (args.size() == 2) {
+    // Compute the target to check (empty means everything).
+    if (!ResolveTargetsFromCommandLinePattern(setup, args[1], false,
+                                              &targets_to_check))
+      return 1;
+    if (targets_to_check.size() == 0) {
+      OutputString("No matching targets.\n");
+      return 1;
+    }
+  }
+
+  if (!CheckPublicHeaders(&setup->build_settings(),
+                          setup->builder()->GetAllResolvedTargets(),
+                          targets_to_check))
+    return 1;
+
   OutputString("Header dependency check OK\n", DECORATION_GREEN);
   return 0;
 }
 
+bool CheckPublicHeaders(const BuildSettings* build_settings,
+                        const std::vector<const Target*>& all_targets,
+                        const std::vector<const Target*>& to_check) {
+  ScopedTrace trace(TraceItem::TRACE_CHECK_HEADERS, "Check headers");
+
+  scoped_refptr<HeaderChecker> header_checker(
+      new HeaderChecker(build_settings, all_targets));
+
+  std::vector<Err> header_errors;
+  header_checker->Run(to_check, &header_errors);
+  for (size_t i = 0; i < header_errors.size(); i++) {
+    if (i > 0)
+      OutputString("___________________\n", DECORATION_YELLOW);
+    header_errors[i].PrintToStdout();
+  }
+  return header_errors.empty();
+}
+
 }  // namespace commands