feat: Add functionality to export proto files

[Eitol]

Feature Description:

Add a new option --proto-out-dir to grpcurl that allows users to generate .proto files for listed, described, or invoked elements and their transitive dependencies.

Functionality:

When using the list and describe verbs, the listed or described elements and their transitive dependencies will be written as .proto files in the specified directory.

Proposed Implementation:
Add a new flag:

protoOut = flags.String("proto-out-dir", "", "The name of a directory where the generated .proto files will be written.")

Use Case:
This feature will be useful for users who need to generate .proto files from gRPC services, especially when working with services that don't have readily available .proto files or when dealing with dynamically generated services.

Tested with the starlink gRPC server.

TEST: OK

closes #474
closes #206

[dragonsinth]

Seems reasonable to me, @jhump wdyt?

[dragonsinth]

you should be able to omit this block, if err is non-nil, f will be nil

[Eitol]

solved

[dragonsinth]

immediately after this block, you should probably defer f.Close()

[Eitol]

you can't defer in a for loop.

See number 2: https://blog.learngoprogramming.com/gotchas-of-defer-in-go-1-8d070894cb01

[dragonsinth]

You have to scope it sometimes:

for _, fd := range allFilesSlice {
	fdFQName := fd.GetFullyQualifiedName()
	dirPath := filepath.Dir(fdFQName)
	outFilepath := filepath.Join(outProtoDirPath, dirPath)
	if err := os.MkdirAll(outFilepath, 0755); err != nil {
		return fmt.Errorf("failed to create directory %q: %v", outFilepath, err)
	}
	fileName := filepath.Base(fdFQName)
	filePath := filepath.Join(outFilepath, fileName)
	err := func() error {
		f, err := os.Create(filePath)
		if err != nil {
			return fmt.Errorf("failed to create")
		}
		defer f.Close()
		if err := pr.PrintProtoFile(fd, f); err != nil {
			return fmt.Errorf("failed to write")
		}
		if err := f.Close(); err != nil {
			return fmt.Errorf("failed to close")
		}
		return nil
	}()
	if err != nil {
		return fmt.Errorf("file %q: %w", filePath, err)
	}
}
return nil

[dragonsinth]

^^ yeah this

[Eitol]

ready

[dragonsinth]

You actually want to error check the close as well. Something like:

err = pr.PrintProtoFile(fd, f)
if err == nil {
  err = f.Close()
}
// do the error check now

you also don't need the final close if you deferred close earlier

[Eitol]

ready

[Eitol]

@dragonsinth hello. Is there anything else to complete?

[dragonsinth]

Let's do one more pass on this, I have a few changes:

• simplify filepath calculations and naming
• improve errors with filename and error wrapping
• 0777 so the system level umask can take effect

func writeProtoFile(outProtoDirPath string, fd *desc.FileDescriptor, pr *protoprint.Printer) error {
	outFile := filepath.Join(outProtoDirPath, fd.GetFullyQualifiedName())
	outDir := filepath.Dir(outFile)
	if err := os.MkdirAll(outDir, 0777); err != nil {
		return fmt.Errorf("failed to create directory %q: %w", outDir, err)
	}

	f, err := os.Create(outFile)
	if err != nil {
		return fmt.Errorf("failed to create proto file %q: %w", outFile, err)
	}
	defer f.Close()
	if err := pr.PrintProtoFile(fd, f); err != nil {
		return fmt.Errorf("failed to write proto file %q: %w", outFile, err)
	}
	return nil
}

[Eitol]

ready

[jhump]

Seems reasonable to me, @jhump wdyt?

Sorry for lack of reply. I've been on a family vacation. FWIW, looks good to me, too 👍.

[rrfheff]

keen to use this feature too, when will we release it?

[victorphamdeveloper]

Keen to use this feature too. Wonder how people deal with this without this feature