Add an assert_no_deps variable to GN.

tools/gn/variables.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/variables.h"
 
 namespace variables {
 
 // Built-in variables ----------------------------------------------------------
 
@@ skipping 373 matching lines @@
     "args: [string list] Arguments passed to an action.";
 const char kArgs_Help[] =
     "args: Arguments passed to an action.\n"
     "\n"
     "  For action and action_foreach targets, args is the list of arguments\n"
     "  to pass to the script. Typically you would use source expansion (see\n"
     "  \"gn help source_expansion\") to insert the source file names.\n"
     "\n"
     "  See also \"gn help action\" and \"gn help action_foreach\".\n";
 
+const char kAssertNoDeps[] = "assert_no_deps";
+const char kAssertNoDeps_HelpShort[] =
+    "assert_no_deps: [label pattern list] Ensure no deps on these targets.";
+const char kAssertNoDeps_Help[] =
+    "assert_no_deps: Ensure no deps on these targets.\n"
+    "\n"
+    "  A list of label patterns.\n"
+    "\n"
+    "  This list is a list of patterns that must not match any of the\n"
+    "  transitive dependencies of the target. These include all public,\n"
+    "  private, and data dependencies, and cross shared library boundaries.\n"
+    "  This allows you to express that undesirable code isn't accidentally\n"
+    "  added to downstream dependencies in a way that might otherwise be\n"
+    "  difficult to notice.\n"
+    "\n"
+    "  Checking does not cross executable boundaries. If a target depends on\n"
+    "  an executable, it's assumed that the executable is a tool that is\n"
+    "  producing part of the build rather than something that is linked and\n"
+    "  distributed. This allows assert_no_deps to express what is distributed\n"
+    "  in the final target rather than depend on the internal build steps\n"
+    "  (which may include non-distributable code).\n"
+    "\n"
+    "  See \"gn help label_pattern\" for the format of the entries in the\n"
+    "  list. These patterns allow blacklisting individual targets or whole\n"
+    "  directory hierarchies.\n"
+    "\n"
+    "  Sometimes it is desirable to enforce that many targets have no\n"
+    "  dependencies on a target or set of targets. One efficient way to\n"
+    "  express this is to create a group with the assert_no_deps rule on\n"
+    "  it, and make that group depend on all targets you want to apply that\n"
+    "  assertion to.\n"
+    "\n"
+    "Example\n"
+    "\n"
+    "  executable(\"doom_melon\") {\n"
+    "    deps = [ \"//foo:bar\" ]\n"
+    "    ...\n"
+    "    assert_no_deps = [\n"
+    "      \"//evil/*\",  # Don't link any code from the evil directory.\n"
+    "      \"//foo:test_support\",  # This target is also disallowed.\n"
+    "    ]\n"
+    "  }\n";
+
 const char kCflags[] = "cflags";
 const char kCflags_HelpShort[] =
     "cflags: [string list] Flags passed to all C compiler variants.";
 const char kCommonCflagsHelp[] =
     "cflags*: Flags passed to the C compiler.\n"
     "\n"
     "  A list of strings.\n"
     "\n"
     "  \"cflags\" are passed to all invocations of the C, C++, Objective C,\n"
     "  and Objective C++ compilers.\n"
@@ skipping 989 matching lines @@
   return info_map;
 }
 
 const VariableInfoMap& GetTargetVariables() {
   static VariableInfoMap info_map;
   if (info_map.empty()) {
     INSERT_VARIABLE(AllDependentConfigs)
     INSERT_VARIABLE(AllowCircularIncludesFrom)
     INSERT_VARIABLE(Args)
     INSERT_VARIABLE(Asmflags)
+    INSERT_VARIABLE(AssertNoDeps)
     INSERT_VARIABLE(Cflags)
     INSERT_VARIABLE(CflagsC)
     INSERT_VARIABLE(CflagsCC)
     INSERT_VARIABLE(CflagsObjC)
     INSERT_VARIABLE(CflagsObjCC)
     INSERT_VARIABLE(CheckIncludes)
     INSERT_VARIABLE(CompleteStaticLib)
     INSERT_VARIABLE(Configs)
     INSERT_VARIABLE(Console)
     INSERT_VARIABLE(Data)
@@ skipping 19 matching lines @@
     INSERT_VARIABLE(Sources)
     INSERT_VARIABLE(Testonly)
     INSERT_VARIABLE(Visibility)
   }
   return info_map;
 }
 
 #undef INSERT_VARIABLE
 
 }  // namespace variables