Allow GN imports to be processed from imports.

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/strings/string_util.h"
 #include "tools/gn/config.h"
@@ skipping 354 matching lines @@
 
 const char kImport[] = "import";
 const char kImport_Help[] =
     "import: Import a file into the current scope.\n"
     "\n"
     "  The import command loads the rules and variables resulting from\n"
     "  executing the given file into the current scope.\n"
     "\n"
     "  By convention, imported files are named with a .gni extension.\n"
     "\n"
-    "  It does not do an \"include\". The imported file is executed in a\n"
-    "  standalone environment from the caller of the import command. The\n"
-    "  results of this execution are cached for other files that import the\n"
-    "  same .gni file.\n"
+    "  An import is different than a C++ \"include\". The imported file is\n"
+    "  executed in a standalone environment from the caller of the import\n"
+    "  command. The results of this execution are cached for other files that\n"
+    "  import the same .gni file.\n"
     "\n"
     "  Note that you can not import a BUILD.gn file that's otherwise used\n"
     "  in the build. Files must either be imported or implicitly loaded as\n"
     "  a result of deps rules, but not both.\n"
     "\n"
     "  The imported file's scope will be merged with the scope at the point\n"
     "  import was called. If there is a conflict (both the current scope and\n"
-    "  the imported file define some variable or rule with the same name)\n"
-    "  a runtime error will be thrown. Therefore, it's good practice to\n"
-    "  minimize the stuff that an imported file defines.\n"
+    "  the imported file define some variable or rule with the same name but\n"
+    "  different value), a runtime error will be thrown. Therefore, it's good\n"
+    "  practice to minimize the stuff that an imported file defines.\n"
     "\n"
     "Examples:\n"
     "\n"
     "  import(\"//build/rules/idl_compilation_rule.gni\")\n"
     "\n"
     "  # Looks in the current directory.\n"
     "  import(\"my_vars.gni\")\n";
 
 Value RunImport(Scope* scope,
                 const FunctionCallNode* function,
                 const std::vector<Value>& args,
                 Err* err) {
-  if (!EnsureSingleStringArg(function, args, err) ||
-      !EnsureNotProcessingImport(function, scope, err))
+  if (!EnsureSingleStringArg(function, args, err))
     return Value();
 
   const SourceDir& input_dir = scope->GetSourceDir();
   SourceFile import_file =
       input_dir.ResolveRelativeFile(args[0].string_value());
   scope->settings()->import_manager().DoImport(import_file, function,
                                                scope, err);
   return Value();
 }
 
@@ skipping 220 matching lines @@
     return found_function->second.executed_block_runner(
         function, args.list_value(), &block_scope, err);
   }
 
   // Otherwise it's a no-block function.
   return found_function->second.no_block_runner(scope, function,
                                                 args.list_value(), err);
 }
 
 }  // namespace functions