Bugfix/early return init files

grpc/src/compiler/python_generator.cc

@@ -130,7 +130,7 @@ class StubGenerator : public BaseGenerator {
                 const Version& version)
       : BaseGenerator(parser, kStubConfig, path, version) {}
 
-  bool Generate() {
+  const char* Generate() {
     Imports imports;
     std::stringstream stub;
     std::string ns_name{};
@@ -150,8 +150,8 @@ class StubGenerator : public BaseGenerator {
   }
 
  private:
-  bool SaveStub(const std::string& filename, const Imports& imports,
-                const std::string& content) {
+  const char* SaveStub(const std::string& filename, const Imports& imports,
+                       const std::string& content) {
     std::stringstream ss;
     ss << "# Generated by the gRPC FlatBuffers compiler. DO NOT EDIT!\n"
        << '\n'
@@ -161,7 +161,8 @@ class StubGenerator : public BaseGenerator {
     ss << content << '\n';
 
     EnsureDirExists(StripFileName(filename));
-    return parser_.opts.file_saver->SaveFile(filename.c_str(), ss.str(), false);
+    return parser_.opts.file_saver->AttemptSave(filename.c_str(), ss.str(),
+                                                false);
   }
 
   void Generate(std::stringstream& ss, const ServiceDef* service,
@@ -246,7 +247,7 @@ class ServiceGenerator : public BaseGenerator {
                    const Version& version)
       : BaseGenerator(parser, kConfig, path, version) {}
 
-  bool Generate() {
+  const char* Generate() {
     Imports imports;
     std::stringstream ss;
 
@@ -282,16 +283,17 @@ class ServiceGenerator : public BaseGenerator {
   }
 
  private:
-  bool SaveService(const std::string& filename, const Imports& imports,
-                   const std::string& content) {
+  const char* SaveService(const std::string& filename, const Imports& imports,
+                          const std::string& content) {
     std::stringstream ss;
     ss << "# Generated by the gRPC FlatBuffers compiler. DO NOT EDIT!\n"
        << '\n';
     FormatImports(ss, imports);
     ss << content << '\n';
 
     EnsureDirExists(StripFileName(filename));
-    return parser_.opts.file_saver->SaveFile(filename.c_str(), ss.str(), false);
+    return parser_.opts.file_saver->AttemptSave(filename.c_str(), ss.str(),
+                                                false);
   }
 
   void GenerateStub(std::stringstream& ss, const ServiceDef* service,
@@ -395,14 +397,14 @@ class ServiceGenerator : public BaseGenerator {
 };
 }  // namespace
 
-bool Generate(const Parser& parser, const std::string& path,
-              const Version& version) {
+const char* Generate(const Parser& parser, const std::string& path,
+                     const Version& version) {
   ServiceGenerator generator{parser, path, version};
   return generator.Generate();
 }
 
-bool GenerateStub(const Parser& parser, const std::string& path,
-                  const Version& version) {
+const char* GenerateStub(const Parser& parser, const std::string& path,
+                         const Version& version) {
   StubGenerator generator{parser, path, version};
   return generator.Generate();
 }

grpc/src/compiler/python_generator.h

@@ -27,11 +27,11 @@
 namespace flatbuffers {
 namespace python {
 namespace grpc {
-bool Generate(const Parser& parser, const std::string& path,
-              const Version& version);
+const char* Generate(const Parser& parser, const std::string& path,
+                     const Version& version);
 
-bool GenerateStub(const Parser& parser, const std::string& path,
-                  const Version& version);
+const char* GenerateStub(const Parser& parser, const std::string& path,
+                         const Version& version);
 }  // namespace grpc
 }  // namespace python
 }  // namespace flatbuffers

include/flatbuffers/code_generators.h

@@ -93,6 +93,10 @@ class BaseGenerator {
  public:
   virtual bool generate() = 0;
 
+  // Modern alternative to bool generate() as this provides a way to
+  // return a specific error message in case of an error and nullptr on success.
+  virtual const char* Generate() { return nullptr; }
+
   static std::string NamespaceDir(const Parser& parser, const std::string& path,
                                   const Namespace& ns,
                                   const bool dasherize = false);

include/flatbuffers/file_manager.h

@@ -33,10 +33,18 @@ class FileSaver {
   virtual bool SaveFile(const char* name, const char* buf, size_t len,
                         bool binary) = 0;
 
+  virtual const char* AttemptSave(const char* name, const char* buf, size_t len,
+                                  bool binary) = 0;
+
   bool SaveFile(const char* name, const std::string& buf, bool binary) {
     return SaveFile(name, buf.c_str(), buf.size(), binary);
   }
 
+  const char* AttemptSave(const char* name, const std::string& buf,
+                          bool binary) {
+    return AttemptSave(name, buf.c_str(), buf.size(), binary);
+  }
+
   virtual void Finish() {}
 
  private:
@@ -52,13 +60,22 @@ class RealFileSaver final : public FileSaver {
  public:
   bool SaveFile(const char* name, const char* buf, size_t len,
                 bool binary) final;
+
+  const char* AttemptSave(const char* name, const char* buf, size_t len,
+                          bool binary) final;
+
+ private:
+  std::string error_msg;
 };
 
 class FileNameSaver final : public FileSaver {
  public:
   bool SaveFile(const char* name, const char* buf, size_t len,
                 bool binary) final;
 
+  const char* AttemptSave(const char* name, const char* buf, size_t len,
+                          bool binary) final;
+
   void Finish() final;
 
  private:

include/flatbuffers/idl.h

@@ -1301,8 +1301,8 @@ bool GenerateJavaGRPC(const Parser& parser, const std::string& path,
 
 // Generate GRPC Python interfaces.
 // See idl_gen_grpc.cpp.
-bool GeneratePythonGRPC(const Parser& parser, const std::string& path,
-                        const std::string& file_name);
+const char* GeneratePythonGRPC(const Parser& parser, const std::string& path,
+                               const std::string& file_name);
 
 // Generate GRPC Swift interfaces.
 // See idl_gen_grpc.cpp.

src/file_manager.cpp

@@ -30,4 +30,13 @@ bool RealFileSaver::SaveFile(const char* name, const char* buf, size_t len,
   return !ofs.bad();
 }
 
+const char* RealFileSaver::AttemptSave(const char* name, const char* buf,
+                                       size_t len, bool binary) {
+  if (!SaveFile(name, buf, len, binary)) {
+    static std::string error_msg;
+    error_msg = "Could not save file " + std::string(name ? name : "unknown");
+    return error_msg.c_str();
+  }
+  return nullptr;
+}
 }  // namespace flatbuffers

src/file_name_manager.cpp

@@ -33,6 +33,12 @@ bool FileNameSaver::SaveFile(const char* name, const char* buf, size_t len,
   return true;
 }
 
+const char* FileNameSaver::AttemptSave(const char* name, const char* buf,
+                                       size_t len, bool binary) {
+  return SaveFile(name, buf, len, binary) ? nullptr
+                                          : "Printing filename failed";
+}
+
 void FileNameSaver::Finish() {
   for (const auto& file_name : file_names_) {
     // Just print the file names to standard output.

src/idl_gen_grpc.cpp

@@ -440,25 +440,26 @@ bool GenerateJavaGRPC(const Parser& parser, const std::string& path,
   return JavaGRPCGenerator(parser, path, file_name).generate();
 }
 
-bool GeneratePythonGRPC(const Parser& parser, const std::string& path,
-                        const std::string& /*file_name*/) {
+const char* GeneratePythonGRPC(const Parser& parser, const std::string& path,
+                               const std::string& /*file_name*/) {
   int nservices = 0;
   for (auto it = parser.services_.vec.begin(); it != parser.services_.vec.end();
        ++it) {
     if (!(*it)->generated) nservices++;
   }
-  if (!nservices) return true;
+  if (!nservices) return nullptr;
 
   flatbuffers::python::Version version{parser.opts.python_version};
-  if (!version.IsValid()) return false;
+  if (!version.IsValid()) return "The provided Python version is not valid";
+
+  auto error = flatbuffers::python::grpc::Generate(parser, path, version);
+  if (error) return error;
 
-  if (!flatbuffers::python::grpc::Generate(parser, path, version)) {
-    return false;
-  }
   if (parser.opts.python_typing) {
-    return flatbuffers::python::grpc::GenerateStub(parser, path, version);
+    auto error = flatbuffers::python::grpc::GenerateStub(parser, path, version);
+    if (error) return error;
   }
-  return true;
+  return nullptr;
 }
 
 class SwiftGRPCGenerator : public flatbuffers::BaseGenerator {