Enhance GN string interpolation.

tools/gn/string_utils_unittest.cc

Index: tools/gn/string_utils_unittest.cc
diff --git a/tools/gn/string_utils_unittest.cc b/tools/gn/string_utils_unittest.cc
index cb5506596892847277fec36049492e44ffc7e513..951a84912750dfa7c554072ac4ee119af882859d 100644
--- a/tools/gn/string_utils_unittest.cc
+++ b/tools/gn/string_utils_unittest.cc
@@ -18,6 +18,16 @@ bool CheckExpansionCase(const char* input, const char* expected, bool success) {
   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('"');
@@ -37,12 +47,13 @@ bool CheckExpansionCase(const char* input, const char* expected, bool success) {
 
   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 #$one", "hello #1", true));
@@ -51,6 +62,8 @@ TEST(StringUtils, ExpandStringLiteral) {
   EXPECT_TRUE(CheckExpansionCase("hello #${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 #$", nullptr, false));
@@ -70,3 +83,17 @@ TEST(StringUtils, ExpandStringLiteral) {
   const char* out = "\"$\\";
   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));
+}