Enhance GN string interpolation.

tools/gn/string_utils_unittest.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 "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/err.h"
 #include "tools/gn/scope.h"
 #include "tools/gn/settings.h"
 #include "tools/gn/string_utils.h"
 #include "tools/gn/token.h"
 #include "tools/gn/value.h"
 
 namespace {
 
 bool CheckExpansionCase(const char* input, const char* expected, bool success) {
   Scope scope(static_cast<const Settings*>(nullptr));
   int64 one = 1;
   scope.SetValue("one", Value(nullptr, one), nullptr);
   scope.SetValue("onestring", Value(nullptr, "one"), nullptr);
 
+  // Nested scope called "onescope" with a value "one" inside it.
+  scoped_ptr<Scope> onescope(new Scope(static_cast<const Settings*>(nullptr)));
+  onescope->SetValue("one", Value(nullptr, one), nullptr);
+  scope.SetValue("onescope", Value(nullptr, onescope.Pass()), nullptr);
+
+  // List called "onelist" with one value that maps to 1.
+  Value onelist(nullptr, Value::LIST);
+  onelist.list_value().push_back(Value(nullptr, one));
+  scope.SetValue("onelist", onelist, nullptr);
+
   // Construct the string token, which includes the quotes.
   std::string literal_string;
   literal_string.push_back('"');
   literal_string.append(input);
   literal_string.push_back('"');
   Token literal(Location(), Token::STRING, literal_string);
 
   Value result(nullptr, Value::STRING);
   Err err;
   bool ret = ExpandStringLiteral(&scope, literal, &result, &err);
 
   // Err and return value should agree.
   EXPECT_NE(ret, err.has_error());
 
   if (ret != success)
     return false;
 
   if (!success)
     return true;  // Don't check result on failure.
+  printf("%s\n", result.string_value().c_str());
   return result.string_value() == expected;
 }
 
 }  // namespace
 
-TEST(StringUtils, ExpandStringLiteral) {
+TEST(StringUtils, ExpandStringLiteralIdentifier) {
   EXPECT_TRUE(CheckExpansionCase("", "", true));
   EXPECT_TRUE(CheckExpansionCase("hello", "hello", true));
   EXPECT_TRUE(CheckExpansionCase("hello #$one", "hello #1", true));
   EXPECT_TRUE(CheckExpansionCase("hello #$one/two", "hello #1/two", true));
   EXPECT_TRUE(CheckExpansionCase("hello #${one}", "hello #1", true));
   EXPECT_TRUE(CheckExpansionCase("hello #${one}one", "hello #1one", true));
   EXPECT_TRUE(CheckExpansionCase("hello #${one}$one", "hello #11", true));
   EXPECT_TRUE(CheckExpansionCase("$onestring${one}$one", "one11", true));
+  EXPECT_TRUE(CheckExpansionCase("$onescope", "{\n  one = 1\n}", true));
+  EXPECT_TRUE(CheckExpansionCase("$onelist", "[1]", true));
 
   // Errors
   EXPECT_TRUE(CheckExpansionCase("hello #$", nullptr, false));
   EXPECT_TRUE(CheckExpansionCase("hello #$%", nullptr, false));
   EXPECT_TRUE(CheckExpansionCase("hello #${", nullptr, false));
   EXPECT_TRUE(CheckExpansionCase("hello #${}", nullptr, false));
   EXPECT_TRUE(CheckExpansionCase("hello #$nonexistant", nullptr, false));
   EXPECT_TRUE(CheckExpansionCase("hello #${unterminated", nullptr, false));
 
   // Unknown backslash values aren't special.
   EXPECT_TRUE(CheckExpansionCase("\\", "\\", true));
   EXPECT_TRUE(CheckExpansionCase("\\b", "\\b", true));
 
   // Backslashes escape some special things. \"\$\\ -> "$\  Note that gtest
   // doesn't like this escape sequence so we have to put it out-of-line.
   const char* in = "\\\"\\$\\\\";
   const char* out = "\"$\\";
   EXPECT_TRUE(CheckExpansionCase(in, out, true));
 }
+
+TEST(StringUtils, ExpandStringLiteralExpression) {
+  // Accessing the scope.
+  EXPECT_TRUE(CheckExpansionCase("hello #${onescope.one}", "hello #1", true));
+  EXPECT_TRUE(CheckExpansionCase("hello #${onescope.two}", nullptr, false));
+
+  // Accessing the list.
+  EXPECT_TRUE(CheckExpansionCase("hello #${onelist[0]}", "hello #1", true));
+  EXPECT_TRUE(CheckExpansionCase("hello #${onelist[1]}", nullptr, false));
+
+  // Trying some other (otherwise valid) expressions should fail.
+  EXPECT_TRUE(CheckExpansionCase("${1 + 2}", nullptr, false));
+  EXPECT_TRUE(CheckExpansionCase("${print(1)}", nullptr, false));
+}