Protobuf: protoc-gen-go: print help when invoked directly

Created on 13 Oct 2016 · 9Comments · Source: golang/protobuf

Flags such as -M and --plugins seem to be entirely undocumented. I expected to find them here or at least be able to run protoc-gen-go --help.

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atombender

👍1

Most helpful comment

When a person encounters a binary that they know nothing about, it's pretty customary to simply invoke the --help flag and expect something useful (even if all it does it link to the README page).

Thus, perhaps calling protoc-gen-go --help should print the help and exit.

dsnet on 9 Mar 2018

👍2

All 9 comments

Finally found them buried in this section.

atombender on 13 Oct 2016

+1 to this. The use of nested flags to set values with plugins such as:
protoc --go_out=plugins=grpc,import_path=mypackage:. *.proto
is rather confusing.

From what I understand, --go_out is a flag that tells protoc to use the protoc-gen-go plugin to compile a proto to golang. Since the protoc-gen-go plugin isn't being called directly it needs to get flags passed in as nested flags. In this case, it's like calling protoc-gen-go with the flags:
--plugins=grpc --import_path=mypackage

The flags are parsed in protoc-gen-go/generator/generator.go

Omustardo on 5 Mar 2017

these nested flags are unfortunate. They raise the learning curve needlessly.

fuzzyami on 27 Mar 2017

👍2

Perhaps this project could consider the "subargs" strategy used by Browserify. It would look something like this:

protoc --go_out [ --plugins=grpc --import_path=mypackage:.* ] *.proto

In other words, whatever is inside the brackets are simply normal flags, but they only apply to go_out.

atombender on 27 Mar 2017

I totally agree, I've been going round endlessly.

bweston92 on 11 May 2017

The nested flags are unfortunate, but follow the convention for other protoc output modes. Consistency is better than inventing our own thing here.

They're all documented in README.md, FWIW:
https://github.com/golang/protobuf#parameters

Having protoc-gen-go print something when invoked directly seems reasonable, although I'm not certain how to detect when that's happened short of vendoring in something like https://github.com/mattn/go-isatty.

neild on 9 Mar 2018

When a person encounters a binary that they know nothing about, it's pretty customary to simply invoke the --help flag and expect something useful (even if all it does it link to the README page).

Thus, perhaps calling protoc-gen-go --help should print the help and exit.

dsnet on 9 Mar 2018

👍2

This is fixed in the v1.20.0 release.

dsnet on 3 Mar 2020

@dsnet could you please confirm what was fixed as part of this or if the steps for checking help is different from what's described above ?

I'm basically trying to list all supported options (more specifically usage of M flag) but this didn't work !

# curl -LkO https://github.com/protocolbuffers/protobuf-go/releases/download/v1.20.0/protoc-gen-go.v1.20.0.linux.amd64.tar.gz
# tar xzvf protoc-gen-go.v1.20.0.linux.amd64.tar.gz
# ./protoc-gen-go --help
protoc-gen-go: unknown argument "--help" (this program should be run by protoc, not directly)