hpb_generator: abrogate output in favour of io::Printer

We unify hpb's impl to utilize Protobuf's canonical printer, as opposed to a bespoke solution.

- augment hpb::Context with EmitLegacy, which keeps the $* syntax while we convert. This allows for a far simpler transitional pathway, and we can incrementally port to .Emit() as we see fit. Of course, all new calls should use .Emit().
- use the Context to wrap io::Printer and any hpb-specific info (e.g. what backend we're using)

PiperOrigin-RevId: 686198921

Author: honglooker

hpb_generator/context.h

@@ -9,13 +9,19 @@
 #define GOOGLE_PROTOBUF_COMPILER_HPB_CONTEXT_H__
 
 #include <memory>
+#include <string>
 #include <utility>
 
+#include "absl/strings/ascii.h"
+#include "absl/strings/str_replace.h"
 #include "absl/strings/string_view.h"
+#include "absl/strings/substitute.h"
 #include "absl/types/source_location.h"
 #include "absl/types/span.h"
+#include "google/protobuf/descriptor.h"
 #include "google/protobuf/io/printer.h"
 #include "google/protobuf/io/zero_copy_stream.h"
+#include "upb_generator/c/names.h"
 namespace google::protobuf::hpb_generator {
 
 enum class Backend { UPB, CPP };
@@ -38,11 +44,8 @@ struct Options {
  */
 class Context final {
  public:
-  Context(std::unique_ptr<io::ZeroCopyOutputStream> stream,
-          const Options& options)
-      : stream_(std::move(stream)),
-        printer_(stream_.get()),
-        options_(options) {}
+  Context(io::ZeroCopyOutputStream* stream, const Options& options)
+      : stream_(stream), printer_(stream_), options_(options) {}
 
   void Emit(absl::Span<const io::Printer::Sub> vars, absl::string_view format,
             absl::SourceLocation loc = absl::SourceLocation::current()) {
@@ -54,19 +57,56 @@ class Context final {
     printer_.Emit(format, loc);
   }
 
+  // TODO: b/373438292 - Remove EmitLegacy in favor of Emit.
+  // This is an interim solution while we migrate from Output to io::Printer
+  template <class... Arg>
+  void EmitLegacy(absl::string_view format, const Arg&... arg) {
+    auto res = absl::Substitute(format, arg...);
+    printer_.Emit(res, absl::SourceLocation::current());
+  }
+
   const Options& options() { return options_; }
+  io::Printer& printer() { return printer_; }
 
   Context(const Context&) = delete;
   Context& operator=(const Context&) = delete;
   Context(Context&&) = delete;
   Context& operator=(Context&&) = delete;
 
  private:
-  std::unique_ptr<io::ZeroCopyOutputStream> stream_;
+  io::ZeroCopyOutputStream* stream_;
   io::Printer printer_;
   const Options& options_;
 };
 
+// TODO: b/373438292 - re-house these 4 legacy funcs post io::Printer move
+inline std::string MessageName(const google::protobuf::Descriptor* descriptor) {
+  return upb::generator::CApiMessageType(descriptor->full_name());
+}
+
+inline std::string ToCIdent(absl::string_view str) {
+  return absl::StrReplaceAll(str, {{".", "_"}, {"/", "_"}, {"-", "_"}});
+}
+
+inline std::string ToPreproc(absl::string_view str) {
+  return absl::AsciiStrToUpper(ToCIdent(str));
+}
+
+inline void EmitFileWarning(const google::protobuf::FileDescriptor* file, Context& ctx) {
+  ctx.EmitLegacy(
+      R"cc(
+        /* This file was generated by hpb_generator (Handle Protobuf) "
+        from the input
+         * file:
+         *
+         *     $0
+         *
+         * Do not edit -- your changes will be discarded when the file is
+         * regenerated. */
+      )cc",
+      file->name());
+  ctx.Emit("\n");
+}
 }  // namespace protobuf
 }  // namespace google::hpb_generator