Carbon fuzzing 2/3: added logic for converting carbon.proto to a Carbon source string. (#1155)

* Carbon fuzzing 2/3: added logic for converting carbon.proto to a Carbon source string.

* adjusted to proto changes in proto PR

* addressed todos

* removed unnecessary has_xx() calls

* minor fix

* sync from part 1

* Update executable_semantics/fuzzing/proto_to_carbon_test.cpp

Co-authored-by: Geoff Romer <gromer@google.com>

* review comments

* Update common/fuzzing/proto_to_carbon.cpp

Co-authored-by: Jon Meow <jperkins@google.com>

* Update common/fuzzing/proto_to_carbon.cpp

Co-authored-by: Jon Meow <jperkins@google.com>

* code review

* code review

* Update common/fuzzing/proto_to_carbon.cpp

Co-authored-by: Jon Meow <jperkins@google.com>

* code review

* merged + added support for type_params in class

* use <> includes for protobuf

* review comments

* code review comments

Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: Jon Meow <jperkins@google.com>

executable_semantics/fuzzing/BUILD

@@ -35,3 +35,25 @@ cc_test(
         "@llvm-project//llvm:Support",
     ],
 )
+
+cc_test(
+    name = "proto_to_carbon_test",
+    srcs = ["proto_to_carbon_test.cpp"],
+    args = [
+        "$(locations //executable_semantics:standard_libraries)",
+        "$(locations //executable_semantics/testdata:carbon_files)",
+    ],
+    data = [
+        "//executable_semantics:standard_libraries",
+        "//executable_semantics/testdata:carbon_files",
+    ],
+    deps = [
+        ":ast_to_proto_lib",
+        "//common/fuzzing:carbon_cc_proto",
+        "//common/fuzzing:proto_to_carbon_lib",
+        "//executable_semantics/syntax",
+        "@com_google_googletest//:gtest",
+        "@com_google_protobuf//:protobuf_headers",
+        "@llvm-project//llvm:Support",
+    ],
+)

executable_semantics/fuzzing/ast_to_proto.cpp

@@ -380,7 +380,14 @@ static auto StatementToProto(const Statement& statement) -> Fuzzing::Statement {
           ExpressionToProto(match.expression());
       for (const Match::Clause& clause : match.clauses()) {
         auto* clause_proto = match_proto->add_clauses();
-        *clause_proto->mutable_pattern() = PatternToProto(clause.pattern());
+        const bool is_default_clause =
+            clause.pattern().kind() == PatternKind::BindingPattern &&
+            cast<BindingPattern>(clause.pattern()).name() == AnonymousName;
+        if (is_default_clause) {
+          clause_proto->set_is_default(true);
+        } else {
+          *clause_proto->mutable_pattern() = PatternToProto(clause.pattern());
+        }
         *clause_proto->mutable_statement() =
             StatementToProto(clause.statement());
       }
@@ -466,6 +473,10 @@ static auto DeclarationToProto(const Declaration& declaration)
       const auto& class_decl = cast<ClassDeclaration>(declaration);
       auto* class_proto = declaration_proto.mutable_class_declaration();
       class_proto->set_name(class_decl.name());
+      if (class_decl.type_params().has_value()) {
+        *class_proto->mutable_type_params() =
+            TuplePatternToProto(**class_decl.type_params());
+      }
       for (Nonnull<const Declaration*> member : class_decl.members()) {
         *class_proto->add_members() = DeclarationToProto(*member);
       }

executable_semantics/fuzzing/ast_to_proto_test.cpp

@@ -5,6 +5,7 @@
 #include "executable_semantics/fuzzing/ast_to_proto.h"
 
 #include <gmock/gmock.h>
+#include <google/protobuf/descriptor.h>
 #include <gtest/gtest.h>
 
 #include <filesystem>
@@ -13,7 +14,6 @@
 #include <variant>
 
 #include "executable_semantics/syntax/parse.h"
-#include "google/protobuf/descriptor.h"
 #include "llvm/Support/Error.h"
 
 namespace Carbon::Testing {

executable_semantics/fuzzing/proto_to_carbon_test.cpp

@@ -0,0 +1,63 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include "common/fuzzing/proto_to_carbon.h"
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+#include "executable_semantics/fuzzing/ast_to_proto.h"
+#include "executable_semantics/syntax/parse.h"
+
+namespace Carbon::Testing {
+namespace {
+
+static std::vector<llvm::StringRef>* carbon_files = nullptr;
+
+// Returns a string representation of `ast`.
+auto AstToString(const AST& ast) -> std::string {
+  std::string s;
+  llvm::raw_string_ostream out(s);
+  out << "package " << ast.package.package << (ast.is_api ? "api" : "impl")
+      << ";\n";
+  for (auto* declaration : ast.declarations) {
+    out << *declaration << "\n";
+  }
+  return s;
+}
+
+TEST(ProtoToCarbonTest, Roundtrip) {
+  int parsed_ok_count = 0;
+  for (const llvm::StringRef f : *carbon_files) {
+    Carbon::Arena arena;
+    const ErrorOr<AST> ast = Carbon::Parse(&arena, f, /*trace=*/false);
+    if (ast.ok()) {
+      ++parsed_ok_count;
+      const std::string source_from_proto = ProtoToCarbon(AstToProto(*ast));
+      SCOPED_TRACE(testing::Message()
+                   << "Carbon file: " << f << ", source from proto:\n"
+                   << source_from_proto);
+      const ErrorOr<AST> ast_from_proto = Carbon::ParseFromString(
+          &arena, f, source_from_proto, /*trace=*/false);
+
+      if (ast_from_proto.ok()) {
+        EXPECT_EQ(AstToString(*ast), AstToString(*ast_from_proto));
+      } else {
+        ADD_FAILURE() << "Parse error " << ast_from_proto.error().message();
+      }
+    }
+  }
+  // Makes sure files were actually processed.
+  EXPECT_GT(parsed_ok_count, 0);
+}
+
+}  // namespace
+}  // namespace Carbon::Testing
+
+auto main(int argc, char** argv) -> int {
+  ::testing::InitGoogleTest(&argc, argv);
+  Carbon::Testing::carbon_files =
+      new std::vector<llvm::StringRef>(&argv[1], &argv[argc]);
+  return RUN_ALL_TESTS();
+}