GN: Change gen command syntax, support relative dirs.

tools/gn/setup.cc

Index: tools/gn/setup.cc
diff --git a/tools/gn/setup.cc b/tools/gn/setup.cc
index 9c0394800cf9714f40a22efb5f68c9a04d8a334c..91201bbc682202fdf264ae5e7b1d31e5ce9635a2 100644
--- a/tools/gn/setup.cc
+++ b/tools/gn/setup.cc
@@ -84,9 +84,6 @@ const char kTimeSwitch[] = "time";
 
 const char kTracelogSwitch[] = "tracelog";
 
-// Set build output directory.
-const char kSwitchBuildOutput[] = "output";
-
 const char kSecondarySource[] = "secondary";
 
 const base::FilePath::CharType kGnFile[] = FILE_PATH_LITERAL(".gn");
@@ -196,7 +193,7 @@ Setup::Setup()
 Setup::~Setup() {
 }
 
-bool Setup::DoSetup() {
+bool Setup::DoSetup(const std::string& build_dir) {
   CommandLine* cmdline = CommandLine::ForCurrentProcess();
 
   scheduler_.set_verbose_logging(cmdline->HasSwitch(kSwitchVerbose));
@@ -212,25 +209,10 @@ bool Setup::DoSetup() {
     return false;
   if (!FillOtherConfig(*cmdline))
     return false;
+  if (!FillBuildDir(build_dir))  // Must be after FillSourceDir to resolve.
+    return false;
   FillPythonPath();
 
-  base::FilePath build_path = cmdline->GetSwitchValuePath(kSwitchBuildOutput);
-  if (!build_path.empty()) {
-    // We accept either repo paths "//out/Debug" or raw source-root-relative
-    // paths "out/Debug".
-    std::string build_path_8 = FilePathToUTF8(build_path);
-    if (build_path_8.compare(0, 2, "//") != 0)
-      build_path_8.insert(0, "//");
-#if defined(OS_WIN)
-    // Canonicalize to forward slashes on Windows.
-    std::replace(build_path_8.begin(), build_path_8.end(), '\\', '/');
-#endif
-    build_settings_.SetBuildDir(SourceDir(build_path_8));
-  } else {
-    // Default output dir.
-    build_settings_.SetBuildDir(SourceDir("//out/Default/"));
-  }
-
   return true;
 }
 
@@ -311,6 +293,23 @@ bool Setup::FillSourceDir(const CommandLine& cmdline) {
   return true;
 }
 
+bool Setup::FillBuildDir(const std::string& build_dir) {
+  SourceDir resolved =
+      SourceDirForCurrentDirectory(build_settings_.root_path()).
+          ResolveRelativeDir(build_dir);
+  if (resolved.is_null()) {
+    Err(Location(), "Couldn't resolve build directory.",
+        "The build directory supplied (\"" + build_dir + "\") was not valid.").
+        PrintToStdout();
+    return false;
+  }
+
+  if (scheduler_.verbose_logging())
+    scheduler_.Log("Using build dir", resolved.value());
+  build_settings_.SetBuildDir(resolved);
+  return true;
+}
+
 void Setup::FillPythonPath() {
 #if defined(OS_WIN)
   // Find Python on the path so we can use the absolute path in the build.