Add unit tests for template invocation.

Adds tests for basic functionality of templates, and athrowing errors for unused variables of various types.

Adds some helpers to set up a test invocation of some GN code.

Adds the ability to capture the output from print() calls in a test.

BUG=

Review URL: https://codereview.chromium.org/228123002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@262468 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 12 insertions, 3 deletions

diff --git a/tools/gn/functions.cc b/tools/gn/functions.cc
index ac1c294..618855b 100644
--- a/tools/gn/functions.cc
+++ b/tools/gn/functions.cc
@@ -532,12 +532,21 @@ Value RunPrint(Scope* scope,
                const FunctionCallNode* function,
                const std::vector<Value>& args,
                Err* err) {
+  std::string output;
   for (size_t i = 0; i < args.size(); i++) {
     if (i != 0)
-      std::cout << " ";
-    std::cout << args[i].ToString(false);
+      output.push_back(' ');
+    output.append(args[i].ToString(false));
   }
-  std::cout << std::endl;
+  output.push_back('\n');
+
+  const BuildSettings::PrintCallback& cb =
+      scope->settings()->build_settings()->print_callback();
+  if (cb.is_null())
+    printf("%s", output.c_str());
+  else
+    cb.Run(output);
+
   return Value();
 }