tools/gn: make defined(foo.bar) an error if !defined(foo)

tools/gn/functions.cc

 // 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 <iostream>
 
 #include "base/environment.h"
 #include "base/strings/string_util.h"
@@ skipping 323 matching lines @@
     "  Returns true if the given argument is defined. This is most useful in\n"
     "  templates to assert that the caller set things up properly.\n"
     "\n"
     "  You can pass an identifier:\n"
     "    defined(foo)\n"
     "  which will return true or false depending on whether foo is defined in\n"
     "  the current scope.\n"
     "\n"
     "  You can also check a named scope:\n"
     "    defined(foo.bar)\n"
-    "  which returns true if both foo is defined and bar is defined on the\n"
-    "  named scope foo. It will throw an error if foo is defined but is not\n"
-    "  a scope.\n"
+    "  which will return true or false depending on whether bar is defined in\n"
+    "  the named scope foo. It will throw an error if foo is not defined or\n"
+    "  is not a scope.\n"
     "\n"
     "Example:\n"
     "\n"
     "  template(\"mytemplate\") {\n"
     "    # To help users call this template properly...\n"
     "    assert(defined(invoker.sources), \"Sources must be defined\")\n"
     "\n"
     "    # If we want to accept an optional \"values\" argument, we don't\n"
     "    # want to dereference something that may not be defined.\n"
     "    if (defined(invoker.values)) {\n"
@@ skipping 21 matching lines @@
       return Value(function, true);
     return Value(function, false);
   }
 
   const AccessorNode* accessor = args_vector[0]->AsAccessor();
   if (accessor) {
     // Passed an accessor "defined(foo.bar)".
     if (accessor->member()) {
       // The base of the accessor must be a scope if it's defined.
       const Value* base = scope->GetValue(accessor->base().value());
-      if (!base)
-        return Value(function, false);
+      if (!base) {
+        *err = Err(accessor, "Undefined identifier");
+        return Value();
+      }
       if (!base->VerifyTypeIs(Value::SCOPE, err))
         return Value();
 
       // Check the member inside the scope to see if its defined.
       if (base->scope_value()->GetValue(accessor->member()->value().value()))
         return Value(function, true);
       return Value(function, false);
     }
   }
 
@@ skipping 413 matching lines @@
   }
 
   // Otherwise it's a no-block function.
   if (!VerifyNoBlockForFunctionCall(function, block, err))
     return Value();
   return found_function->second.no_block_runner(scope, function,
                                                 args.list_value(), err);
 }
 
 }  // namespace functions