add ast::Module::to_str

This makes it easier to see the bug.

Bug: tint:22
Change-Id: Ic5acc0b8299ef31eb73b49863bc42ac09de6e9bf
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/17203
Reviewed-by: dan sinclair <dsinclair@google.com>

src/ast/module.cc

diff --git a/src/ast/module.cc b/src/ast/module.cc
index dfca88a..8b69af0 100644
--- a/src/ast/module.cc
+++ b/src/ast/module.cc
@@ -59,21 +59,24 @@
 std::string Module::to_str() const {
   std::ostringstream out;
 
+  out << "Module{" << std::endl;
+  const auto indent = 2;
   for (const auto& import : imports_) {
-    import->to_str(out, 0);
+    import->to_str(out, indent);
   }
   for (const auto& var : global_variables_) {
-    var->to_str(out, 0);
+    var->to_str(out, indent);
   }
   for (const auto& ep : entry_points_) {
-    ep->to_str(out, 0);
+    ep->to_str(out, indent);
   }
   for (const auto& alias : alias_types_) {
     out << alias->name() << " -> " << alias->type()->type_name() << std::endl;
   }
   for (const auto& func : functions_) {
-    func->to_str(out, 0);
+    func->to_str(out, indent);
   }
+  out << "}" << std::endl;
 
   return out.str();
 }

src/ast/module_test.cc

diff --git a/src/ast/module_test.cc b/src/ast/module_test.cc
index 64fd31b..7fad54b 100644
--- a/src/ast/module_test.cc
+++ b/src/ast/module_test.cc
@@ -14,9 +14,10 @@
 
 #include "src/ast/module.h"
 
+#include <sstream>
 #include <utility>
 
-#include "gtest/gtest.h"
+#include "gmock/gmock.h"
 #include "src/ast/entry_point.h"
 #include "src/ast/function.h"
 #include "src/ast/import.h"
@@ -34,6 +35,13 @@
   EXPECT_EQ(m.imports().size(), 0);
 }
 
+TEST_F(ModuleTest, ToStrEmitsPreambleAndPostamble) {
+  Module m;
+  const auto str = m.to_str();
+  const auto expected = "Module{\n}\n";
+  EXPECT_EQ(str, expected);
+}
+
 TEST_F(ModuleTest, Imports) {
   Module m;
 
@@ -44,6 +52,16 @@
   EXPECT_EQ("std::glsl", m.imports()[0]->name());
 }
 
+TEST_F(ModuleTest, ToStrWithImport) {
+  Module m;
+  m.AddImport(std::make_unique<Import>("GLSL.std.430", "std::glsl"));
+  const auto str = m.to_str();
+  EXPECT_EQ(str, R"(Module{
+  Import{"GLSL.std.430" as std::glsl}
+}
+)");
+}
+
 TEST_F(ModuleTest, LookupImport) {
   Module m;